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I’m purchasing a 1st gen Honda Insight soon, and I’m already thinking about mods to increase the MPG.

Anyone have any suggestions?

Here’s what I’m thinking so far

  • lightweight wheels (still looking, taking recommendations)
  • high MPG tires (still looking, taking recommendations)
  • weight reduction—removing passenger seat, removing sound insulation, installing lighter weight driver seat
  • hot air intake
  • coilovers to lower the car and reduce drag coefficient
This will be a daily driver, but I am perfectly fine being uncomfortable. Needless to say, I’ll never have a passenger.
 

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Heheh...

Welcome to the club. :)

The easiest way to get better fuel economy is to adjust the nut behind the steering wheel. ;) That means if you haven't ever driven an Insight before, there is a learning curve to spectacular fuel economy.

The next best and easiest things you can do for MPG are to make sure that your car is in tip-top shape. That means all underbody panels and spats present, correct tires inflated to the correct PSI, EGR plate clean, EGR valve functional, no error codes. It will help immensely to get a specimen with a powerful engine. A compression test will go a long way towards comparing different engines; the butt dyno is notoriously unreliable.

Once all of that is taken care of, you can start to think about things like hot air intake.
 

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Please don't remove your interior. There is already barely any sound deadening and removing your seat won't really have an noticable effect.

As said above, give it a tune up, run M1 0W16 oil, install a belly pan and fix any under body aero it needs, get LRR tires. I've owned one for years and it's always a challenge to drive it efficiently.
 

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I agree with previous two comments. Driving skill is most important. But....

I once obsessed on MPG, both in competition, and regular driving. (See my signature.) Some of what you mention is useless or counterproductive, particularly bullets one and two - you won't find better tires or wheels than the OEM. Yes, once you have gotten what you can out of driving technique, then a hot air intake off the 1st catalytic will help a bit.

I ran out of desire before I got around to lowering the car, but reconsidered it. I don't think I'd go as far as coil overs if I wanted to do this. I'd just cut the springs a bit - much cheaper. You are very limit in how much lowering you can do. Lie on the ground and look at the suspension travel available in the rear. You only have about 2 inches, which is easily taken up in tight turns. The famous Insight "thump," accompanied by increased oversteer, is caused by bottoming - even with stock height. Scott's springs help a lot on this problem. (While under there, look at that shiny spot on the metal stop, just over the bump rubber - if you doubt.)

A Forced Auto Stop(FAS) circuit will hype your MPG faster than about any other mod. MPG goes up very rapidly when the engine isn't running ;)

There are 3 aero improvements which will improve MPG to some unknown degree. Most states allow removal of the right side mirror which helps slightly. Tests on ecomodder have consistently shown about 3% improvement for both mirrors or 1 1/2% for one.

Airflow through the engine compartment is very lossy aerodynamically. In much of the year, you can safely block much of the lower opening, and all of the top opening. I blocked about 90% of the lower opening, with a small opening just in front of the radiator. You MUST have a separate means of monitoring the coolant temp because the dash gauge is notoriously slow and inaccurate.

Last, a full underbelly helps. Scott's front underbelly is very helpful in smoothing out the flow in front of the crossover attachment(the most important area aerodynamically), but you are left with some "dirty" area around the lower A-arms which can be improved. There is a huge "dirty" area in back between the fuel tank and the rear bumper which can be smoothed out. It goes without saying that your regular Honda plastic mid panels need to be in place.
 

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As above.

The seats are ridiculously light and unless you are going to a fiberglass/carbon fiber type race seat you won't save anything. Weight is not the problem in these cars. There is precious little you can do in the form of weight reduction which will make ANY noticable impact in your daily MPG's.

The best tires for efficiency are the stock Potenza's.

The stock wheels are already some of the lightest ever built by an OEM.

Hot air intake mod is OK unless you live somewhere hot like me. My IAT is over 120 in the summer already.

Lowering the car makes very little difference.

The things that make the BIGGEST difference are a good "stage zero" which is catching up on all neglected maintenance and putting in good, fresh fluids. Make sure the EGR plate is clean, Good stock indexed plugs, Clean catilytic converter(s), and probably the biggest of all make sure all the under body aero is in place and in great shape. You CAN upgrade to one of Scott's skidplates to help with this. That is money well spent.

Also higher than normal tire pressures make a difference.


After all this just drive it and learn to hypermile if that's your thing. Once you top out on your MPG averages look into some of the mods that are popular here. FAS, Calpod, Mima, and maybe even an updated battery pack if you're savvy.


FWIW, you don't NEED a good battery to get great MPG's. If your battery is toast I would just bypass it and save up for a lithium option instead of trying to fix the stock pack. NiCad's and NiMh's (stock battery) are pretty well done for. You'll waste a lot of money and not be satisfied trying to fix up the stock pack. If yours is working however, keep it working! That's free money right there.
 

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A stock car with a partial grille block and 45-50psi in the tires will cruise at 90-105mpg at ~50mph. I wasn't able to squeeze much more out, even doing things like removing the mirrors and rear wiper and more thorough underbody paneling. Weight seemed to affect fuel economy very little on the open highway. Engine-off coasting DOES work, but it adds a fair bit of fiddling just to drive in a straight line.

I'd say block 75% of your grille, air the tires up, and install a kill switch of FAS and learn how to game the IMA system - I was still figuring this out after years of owning the car.
 

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<snip>

Engine-off coasting DOES work, but it adds a fair bit of fiddling just to drive in a straight line.

<snip>
This concept eludes me. It will take a certain amount of heat to move a certain amount of weight with a certain amount of drag a certain distance. Over the road trucks find their greatest efficiencies at a fixed speed/RPM for the longest possible distance. I know of no trucking company that uses the accelerate/coast method to increase MPG. Likewise ships and airplanes. So I wonder how it would then apply to automobiles. Has there ever been, say, side by side testing? One car driving 200 miles at a constant rate alongside the same make and model using the accelerate/coast method? This would move this from conjecture to tested fact. In short, I remain unconvinced until I see real proof.
 

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NiCad's and NiMh's (stock battery) are pretty well done for. You'll waste a lot of money and not be satisfied trying to fix up the stock pack.
Toyota is still producing brand new cars with NiMH packs. They're not done yet.
 

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This concept eludes me. It will take a certain amount of heat to move a certain amount of weight with a certain amount of drag a certain distance. Over the road trucks find their greatest efficiencies at a fixed speed/RPM for the longest possible distance. I know of no trucking company that uses the accelerate/coast method to increase MPG. Likewise ships and airplanes. So I wonder how it would then apply to automobiles. Has there ever been, say, side by side testing? One car driving 200 miles at a constant rate alongside the same make and model using the accelerate/coast method? This would move this from conjecture to tested fact. In short, I remain unconvinced until I see real proof.
It works because of parasitic losses.

Consider: At full throttle at 2000rpm, let's say it takes 3hp to overcome friction in all of the bearings, between the piston rings and piston walls, to overcome friction in the belts, to compress the springs in the valvetrain, to turn the water pump, oil pump, basically just to spin the engine.

It takes the same 3hp to spin the engine at half throttle, and the same at 0% load at 2000rpm - the engine still burns fuel just to spin, and quite a bit, because it's driving things like water and oil pumps and has a bunch of belts and other frictional components attached to it.

Cruising along at 55mph, the engine is loaded at around 50% (a hair more, typically, but let's round it to 50% for my argument).

Let's say that at 55mph, our cars need 12hp to maintain speed, to overcome aero drag, rolling resistance and drivetrain losses. Our engines need to burn enough fuel to make 15hp because 3hp of that is just turning the engine, doing no useful work.

It stands to reason then, that if you ran the engine half the time at 100% load, and coasted with the engine off the other half of the time, over time you'd have half of the parasitic losses. Half the time you wouldn't be turning the water pump, oil pump, belts, camshafts, etc. It would be equivalent to reducing drag by 1.5hp and overall would save fuel.

This is the same reason you get better fuel economy in 5th gear than in, say, 3rd gear. The parasitic losses in 3rd are higher than in 5th because RPM is around twice as high, and the ratio of useful work to parasitic losses is much worse. The engine might be using 6hp just to spin at 4000rpm, meaning you need to burn enough fuel to make 18hp at the same 55mph in 3rd gear.

Pulse and glide driving is similar to if we could have a hypothetical 6th gear that was just tall enough that our cars would barely maintain speed at 55mph with the pedal to the floor. While the engine is running, it has the best possible ratio of useful work to losses.
 

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I do not want to get in a long drawn out discussion about this. Acceleration eats up gas. By eliminating acceleration a huge drain is elliminated. Back to my questiion, if this works why don't ships use it? If it works why don't commercial trucks use it? If it works why don't airplanes use it? Until you can provide more than conjecture I remain unconvinced. This is untested. One test is worth a thousand opinions. Where's the beef?
 

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Well.. It should be entirely possible to pulse and glide in a big rig; I bet there are a few hypermiling truckers out there who have done it. An airplane should be really good at pulse and glide. Ships as in container ships, probably not so much given that their engines operate at peak efficiency all the time, and water is 50x more dense than air. Not sure how much the latter plays a role.

I think the reason you don't see people doing pulse and glide in these vehicles is simply because of time. They're on a schedule where time is money - money that easily overrides any potential fuel savings.

A peek at the BSFC chart for the Insight engine shows that accelerating at ~3/4 throttle at 2500-3500RPM is more efficient than cruising at 1500RPM, a (purely estimated) difference of around 25-35 grams of fuel per kWh of energy produced.

84682


But since you wanted beef, this paper contains a whole cow's worth. ;)
 

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I'll look for some independent tests in a bit, but I was sold on it when I tried it in my old Del Sol with an Integra B18C engine.

That car had very aggressive gearing. 5th gear was like 3rd gear in our Insights. At 70mph it was turning a 1.8L at something like 4500rpm, it could have used another 4+ gears on top of that on the highway. Driving in a straight line at steady speed it would deliver around 28mpg at 70mph, and I could see as high as maybe 35mpg at 55. By practicing pulse and glide, I could see as high as 50-55mpg, but it was a lot of work.

Modern transmissions virtually eliminate the need for pulse and glide by having a very wide spread of ratios.

The CVT in the G1's top ratio is hardly taller than 4th gear in the manual, because it was an early an immature technology for automotive applications. That's part of the reason CVT Insights don't get nearly the same highway fuel economy - they lack the top gearing. However, a modern Civic CVT can get the Civic 1.5L down to maybe 1400rpm at the same speeds the Insight's ridiculously tall 5MT would be at 2000rpm. That engine is running at full load, so there's zero need for pulse and glide.

Probably the quickest and easiest demonstration I can show in the real world is by linking my fuel logs I keep on Ecomodder. For a while, my 2.4L swapped Insight had an inoperable 6th gear, so I was driving around in a lower gear. I was averaging low 40's MPG in summer. However, on a trip back from Boston I tried pulse and glide the entire way (quite exhausting), and when I filled up the tank, I had averaged 65mpg.

84683


You're right in that a chassis takes a fixed amount of heat to push down the road. P&G doesn't reduce that, it just cuts the amount of losses and improperly geared engine imparts.

Edit: read here.


Edit2: As for jet engines, they operate a bit differently. The most equivalent thing for them is the "bypass ratio". Read about it here:

 

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I do not doubt your faith in pulse and glide. I am not surprised that you can muster graphs and charts. But until there is an actual test this is all unproven conjecture and no more. Show me the proof where this is fact. If pulse and glide were an effective technique I'll bet it would be built into long haul trucks. Or maybe the idea of a bunch of vehicles accelerating and slowing on interstates is just too scary to contemplate. There is no free lunch. But I will gladly admit I am wrong when I see proof, as in tested. I wrote code for 20 years and it is no accident that our motto was, "One test is worth a thousand opinions."

I am somewhat surprised that this has never been tested. It would be easy to do within the Insight Central community itself. Get ten or twelve Insights together and have half do pulse and glide and the other half drive ordinarily. Do that over two or three hundred miles a few times alternating who uses pulse and glide and who does not. Then evaluate the results.
 

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Did you read the link I sent?

Pulse & glide in a Geo Metro

Still skeptical, I went out in my car with the ScanGauge. I really didn't believe it was going to work, but here are the numbers I saw. I went to my "test course" - a nearly perfectly level stretch of 2-lane highway about 6.5 km long - but these numbers aren't meant to be taken as experimentally valid. I only did one run, so consider yourself warned. It's just a snapshot:

At a steady 80 km/h (about 50 mph) I was getting 59 mpg (US) (there was a tail wind)
"gliding" down from 90 to 70 km/h took 16 seconds
pulse & glide results - Firefly

"pulsing" back up from 70 to 90 km/h at a rate of acceleration that also took 16 seconds I was getting about 34 mpg (US)
So my pulse and glide average would be 68 mpg, vs. 59 at the same average speed. That's a 15% increase over the steady state mpg - theoretically.
I say theoretically because the engine would have to be off in the glide to get that mileage. You could do it, but it adds another step in an already arguably impractical process (remember the engine shuts off automatically in the Prius when you lift off the accelerator).

So I took a couple more readings. With the engine idling, and the car in neutral, the average mpg shown on the ScanGauge in the glide down from 90-70 km/h was 550 mpg. When you average that against the 34 mpg of the pulse, it works out to an average of 64 mpg. Now we're at an 8% increase over the steady-state mpg.

pulse & glide chart - Prius

I would name the difference between the two techniques "full" pulse & glide (neutral, with engine off in the glide) vs. "mild" (neutral, with engine idling in the glide).

So, now you know the next time you find yourself cruising down a lonely road at a steady speed, you're not getting the best mileage you could. You could be pulsing & gliding to maintain the same average speed, and saving lots of fuel in the process.

To exceed your steady-state mpg (X), you just have to be able to "pulse" at a rate of fuel consumption that is greater than half of X (assuming equal length pulses & glides; you may be able to increase the proportion of glide to pulse - meaning faster acceleration in the pulse, or glides that are timed to take advantage of descending a grade - and still beat your steady-state mpg for that average speed). You can see how fuel economy instrumentation plays a critical role in determining the best rate of pulse to make this work.
I'll see if I can find something from the US government, or perhaps a university.
 

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Here are some references for you:


The way in which a vehicle is driven significantly affects its fuel consumption. This paper analyses the fuel-optimal driving strategies of a traditional vehicle equipped with a continuously variable transmission in car-following scenarios. A minimal-fuel-consumption problem is formulated, which is numerically solved using the Gauss pseudospectral method. The identified optimal manoeuvres were found to demonstrate two types of behaviour depending on the vehicle speed: pulse-and-gliding (PnG) and constant speed (CS). Further analyses indicate that the difference in behaviours mainly depends on the engine fuelling characteristics (both static and transient) and the road load. As the preceding vehicle’s speed increases, the optimal manoeuvre changes from partial PnG to full PnG, and finally to CS. In the full-PnG strategy, the engine switches between the minimum brake specific fuel consumption point and the idling point while the range error oscillates between its upper and lower bounds. The period, duty cycle percentage, and fuel economy improvement of the PnG strategy are analysed and presented.

The goal of many competitions and challenges held in North America and Europe is to achieve extremely low fuel consumption. A possible strategy to reduce fuel consumption is to use the vehicleâ s fuel converter such as an engine to accelerate the vehicle to a high speed and coast to a lower speed with the engine off. This method will reduce fuel flow to zero during the coast phase. Also, the vehicle uses higher power engine load to accelerate to the upper vehicle speed in a limited time, thus increasing the engine brake thermal efficiency. This strategy is known as â pulse and glideâ or â burn and coastâ in some references. In this study, the â pulse and glideâ (PnG) method is first applied to a conventional vehicle to quantify the fuel consumption benefits when compared to steady speed conditions over the same distance. After that, an HEV is used as well to investigate if a hybrid system can further reduce fuel consumption with the proposed strategy. Note that the HEV used in this study has the advantage that the engine can be automatically shut off below a certain speed (~40 mph) at low loads, however a driver must shut off the engine manually in a conventional vehicle to apply this driving strategy. In this document, three preliminary results of the PnG driving strategy are presented; (1) improved fuel economy for a conventional vehicle from a simple spread sheet model, (2) improved fuel economy for an HEV from a dynamic vehicle simulation model (the Powertrain Analysis Toolkit (PSAT)) and (3) improved fuel economy for an HEV from vehicle testing at Argonne National Laboratory (ANL), all compared to steady speed conditions. The preliminary results show that the impact of engine load and kinetic energy stored in vehicle inertia is significant for fuel consumption using a PnG driving strategy compared to steady speed driving at the same average speed case. Especially, fuel economy can be improved at low speed range and higher acceleration because the aerodynamic drag force is smaller at low speed and the engine is running in a more efficient region for a short period of time respectively. In the last section, proposed directions of research are addressed based on the preliminary results.
And our favorite and most reliable source, Wikipedia:


Pulse and glide[edit]
See also: Bang-bang control
Pulse and glide (PnG) or burn and coast driving strategy consists of rapid acceleration to a given speed (the "pulse" or "burn"), followed by a period of coasting or gliding down to a lower speed, at which point the burn-coast sequence is repeated.[24][25] Coasting is most efficient when the engine is not running, although some gains can be realized with the engine on (to maintain power to brakes, steering and ancillaries) and the vehicle in neutral.[25] Most modern petrol vehicles cut off the fuel supply completely when coasting (over-running) in gear, although the moving engine adds considerable frictional drag and speed is lost more quickly than with the engine declutched from the drivetrain.

The pulse-and-glide strategy is proven to be an efficient control design both in car-following[25] and free-driving scenarios,[26] with 20% fuel saving. In the PnG strategy, the control of the engine and the transmission determines the fuel-saving performance, and it is obtained by solving an optimal control problem (OCP). Due to a discrete gear ratio, strong nonlinear engine fuel characteristics, and different dynamics in the pulse/glide mode, the OCP is a switching nonlinear mixed-integer problem.[27][28]

Some hybrid vehicles are well-suited to performing pulse and glide.[29] In a series-parallel hybrid (see hybrid vehicle drivetrain), the internal combustion engine and charging system can be shut off for the glide by simply manipulating the accelerator. However based on simulation, more gains in economy are obtained in non-hybrid vehicles.[24][25]

This control strategy can also be used in vehicle platoon (The platooning of automated vehicles has the potential of significantly enhancing the fuel efficiency of road transportation), and this control method performs much better than conventional linear quadratic controllers.[30]

Pulse and glide ratio of combustion engine in hybrid vehicles points on it by gear ratio in its consumption map, battery capacity, battery level, load, depending on acceleration, wind drag and its factor of speed.

Causes of pulse-and-glide energy saving[edit]
Much of the time, automobile engines operate at only a fraction of their maximal efficiency,[31] resulting in lower fuel efficiency (or what is the same thing, higher specific fuel consumption (SFC)).[32] Charts that show the SFC for every feasible combination of torque (or Brake Mean Effective Pressure) and RPM are called Brake specific fuel consumption maps. Using such a map, one can find the efficiency of the engine at various combinations of rpm, torque, etc.[25]

During the pulse (acceleration) phase of pulse and glide, the efficiency is near maximal due to the high torque and much of this energy is stored as kinetic energy of the moving vehicle. This efficiently-obtained kinetic energy is then used in the glide phase to overcome rolling resistance and aerodynamic drag. In other words, going between periods of very efficient acceleration and gliding gives an overall efficiency that is usually significantly higher than just cruising at a constant speed. Computer calculations have predicted that in rare cases (at low speeds where the torque required for cruising at steady speed is low) it's possible to double (or even triple) fuel economy.[24] More realistic simulations that account for other traffic suggest improvements of 20% are more likely.[25] In other words, in the real world one is unlikely to see fuel efficiency double or triple. Such a failure is due to signals, stop signs, and considerations for other traffic; all of these factors interfering with the pulse and glide technique. But improvements in fuel economy of 20% or so are still feasible.[24][25][33]
 

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I posted the paper cited in the Wiki. Its called "Strategies to minimize the fuel consumption of passenger cars during car-following scenarios"
By S Eben Li and H Peng
From Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA

It has a detailed section on pulse and glide, with lots of fancy math and graphics.

Not sure what more you want... :p
 

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I remain skeptical on the acknowledged counterintuitiveness. The quoted papers are supportive and convincing. You would not have cited them if hey were not. If I get some time I will poke around and see what I can find. You may be entirely right and I may be entirely wrong. On a scholastic level these are single studies and I do not know if they have been peer-reviewed. One thing is for sure and that is that I will gladly pay the difference not to put up with this method. And if the assumption proves true that it does work do not lose sight that you are exposing yourself to real risk with this slowing down and accelerating when it is done on a highway, or worse, on an interstate. This is not as risky as taking off your front brakes to save gas but it is close. As usual, YMMV.
 

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And that's likely why I was unable to find any government sources.

I personally can't see the harm in shutting off my engine when rolling downhill on the highway on a grade where I can maintain speed, and bump starting it back up at the bottom to climb the other side - especially since our cars maintain both power steering and braking without the engine running.

Probably the easiest way to verify this yourself would be to just try it. The Insight doesn't gain as much as most other vehicles of that era from P&G because it's already very well geared - the amount you gain is proportional to the losses - but they're measurable.
 

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So when doing P&G do you shift into neutral when gliding? Or do you jsut give barely any throttle? I've never tried it. 20% fuel savings sounds amazing.
 

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So when doing P&G do you shift into neutral when gliding? Or do you jsut give barely any throttle? I've never tried it. 20% fuel savings sounds amazing.
Pulse and glide doesn't work if you leave it in gear. If left in gear, your engine is still generating a lot of parasitic losses, spinning your water and oil pump (among other things) at high RPM. This is, in fact, generally referred to as "engine braking".

I can think of two ways to do P&G:

1) Accelerate in 5th gear to a few mph over your target speed. Drop it into neutral (engine RPM drops), coast down to a few mph below your target speed. Put it back in gear, repeat.

2) Accelerate in 5th gear to a few mph over your target speed. Drop it in neutral. Kill the engine somehow. Coast down to a few mph below your target speed. Put it back in gear and bump start the engine. Repeat.

The key is that the engine RPM drops, preferably to zero. Pulse and glide with the engine idling between pulses still shows gains, but they're typically half as much as "engine off coasting" because the engine still consumes fuel while idling.

There are a few ways to kill the engine.

My favorite is Natalya's Forced Auto Stop mod. This basically sends a signal to your ECU that your car is below 19mph and you've tapped the brake, resulting in auto stop until you put the car back into gear, at which point it will restart just like you're putting it back in gear at a stoplight. The engine will also automatically restart if your brake vacuum gets too low - it has all of the safeties Honda built in to ensure you could safely coast without the engine running under 19mph, just at any speed.

Another method is to put a relay in line to your fuel injector grounds, which you activate with a switch. This is what I've done with previous cars and did in my Insight until Natalya came up with her awesome mod.

A third method, least good in my opinion, is to cut off the fuel pump. The wiring is the easiest, but fuel pressure doesn't stop immediately.

Options 2 and 3 will rarely cause a CEL, option 1 never does.

Pulse and glide is easiest if you live in an area with rolling hills - simply drive up one side of the hill normally, then put the engine in auto-stop and roll down the other side. I've had trips in my car (with the original engine) as high as 120-130mpg doing mild engine-off coasting in rolling hills.
 
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