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Old 06-21-2011, 07:24 PM   #1 (permalink)
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Default Stuck at 55mpg!

I am new to this forum, and also a new owner to the insight. I've had it for just under 2 months now. When I drove it back to PA from Illinois, I got around 65-70mpg.
Everyday I drive 90 miles round trip to work. It seems I have been stuck at the 55mpg range for weeks now.
It also seems that it is more fuel efficient in 4th gear around 65mph then it is in 5th gear (is this correct)?


Sorry about the random questions..just looking for some answers!

Thanks in advance!
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Old 06-21-2011, 07:42 PM   #2 (permalink)
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It's really difficult.. nearly impossible to say, really.. without being able to drive your route. The Insight is very sensitive to environmental conditions.. It could be any one of a dozen different things..

It's funny, I've seen the 4th vs. 5th gear thing mentioned several times in the last few days and I too experienced this when I was a new Insight owner.

With practice, you will find that the tallest gear you can possibly be in for your speed will always give the best fuel economy. I am guessing that the reason some of us find that 4th gear seems "better" at first, is because we are used to having power on tap. You can still easily lean burn in 4th gear, but pressing the gas pedal actually nets you some noticeable power. The consequence of this is that the instantaneous MPG display is just that much more touchy than it is in 5th gear - it's very easy to kick out of lean burn mode in 4th.

Do you find that you're able to get better fuel economy one way than the other, and 55MPG is your net? If so, it could just be your route.

Have you tried slowing down a little to see what that can do to your numbers? Even 60 instead of 65MPH can make a big difference, again depending on your specific driving conditions. Try 55MPH too, if you can.

My guess is that after only 2 months, you have not completely learned the intimacies of lean burn mode and the extremely small pedal movements required to work with it effectively.

Take your car out onto your route when you're not in a rush to get to/from work and there isn't much traffic, and play with it a bit. See what kind of fuel economy you can get cruising along at different speeds. For example, cruise along at 55MPH and 75MPG - or whatever the number that you're able to maintain is. Practice moving the instantaneous MPG display in 5MPG increments up and down the display, from 120MPG down to ~60MPG and back up again, noting what this does to your available power and speed. Learn to recognize lean burn mode, and how far down you can press the pedal before you feel that surge of power as you lose lean burn and the MPG drops down to 45-50. I can't stress small movements of the pedal enough - I haven't actually measured, but I would estimate that I move my foot 1-2mm at a time.

Are you running OEM tires, and at what PSI?
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Last edited by Eli; 06-21-2011 at 07:52 PM.
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Old 06-23-2011, 10:32 AM   #3 (permalink)
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Long trips for me are ALWAYS net far better fuel economy than shorter trips.

With shorter trips, you are in effect amortizing even minor accelrations over fewer highway miles. I know in my CVT car when I go rowing about 7 miles from my home, my segment milege is only about 29 mpg by the time I get to the highway and accelerate up to 55 (my normal crusing speed, where I can usually see a solid 65 MPG in the instantanious readout, and sometimes MUCH more). By the time I get to my destination though the MPG average will usually have climbed up to between 60 and 70 MPG.

But when I turn around to come back, by the time I get back to the highway from the dock, in as little as 1.4 miles, the average will have fallen back to around 55 MPG.

So, on a relativly short trip (75 miles even), unless you can hold EXACT speeds or can pulse and glide without disrupting traffic, EVERY small acceleration really bits into fueld economy.

On long distance trips, ESPECIALLY in FLAT FLAT FLAT Illinois, holding a specific speed is MUCH easier, and you don't have a lot of accelerations.

Also, the AC is a huge drain on mileage. I assume that it was very cool when you brought the car home.

If you are running the AC, expect a 10 to 15 MPG hit depending on the heat.

Around town in Austin Tx, it is so hot during the summer that the AC compressor is on a LOT. This drags my mileage down to about 40 sometimes. The problem for me is that it is so hot that if I use Autostop, I bake even at stoplights.

Spring and fall, and mild winter days, I can pull 65 MPG segments all day long (and this is in a CVT), so the AC is a real killer.
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Old 06-23-2011, 11:32 AM   #4 (permalink)
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I'm not sure where exactly the maximum efficiency point for load is on the engine but I've found that if I can keep engine load capped to 80% under lean-burn I can get better gas mileage overall, so if I drop to 4th gear and push 70% load, I'll still be at 75MPG but getting a little extra acceleration out of the engine at the same fuel consumpsion. Sometimes I'll be pushing 65MPG going up a hill in 4th gear versus trying to hold 70mpg up in hill in 5th gear, both under lean-burn and I'll actually get better overal mileage because I'll get back to 5th gear sooner because the speed recovers better and the actual distance travelled at 65MPG is quite a bit shorter with the added performance.

If I can cruise at the speed I can without pushing more fuel through than 80MPG I'll stay in 5th but if I've got a few hills ahead and don't want to lose speed, many times 4th gear helps a bunch versus losing lean-burn. I haven't seen much difference in just dropping lean-burn and pushing the max performance 95% load at roughly 3/4 throttle (under 80 TPS on the Scangauge) because it doesn't drop below stoich fuel ratio and then once up to enough speed, snag lean-burn again right away. Depends on my level of patience but gas mileage was pretty good on the way back from St Louis toward the end of winter using that trick. If its for a moderate hill that I'm coming up to often I prefer to make the gear switch while its in a lean-burn purge and that way I'm not dropping out of lean-burn during the ideal part of the cycle.
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Old 06-23-2011, 12:22 PM   #5 (permalink)
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HaHa, I'm going to guess a new owner would have no idea what MN just said. But I have been driving mine since last July and I understand completely.

Basically Cah155, it just takes time and reading these posts can really help. Another great help is a gauge like the Ultra-Gauge which happens to be cheap right now: UltraGauge Automotive Information Center and OBDII Scan Tool.

That gauge has made lean-burn so much clearer to me. Entering or leaving LB is subtle, seat of the pants identified. I can look at the gauge and see throttle position movement, engine load, and state of O2 sensors and really have an idea what is going on. Good Luck!
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Old 06-23-2011, 01:59 PM   #6 (permalink)
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Set the A/C from either "Auto" or "ECON - A/C ON" to "ECON - A/C OFF" and your mileage will return to normal.

Current warm temperatures for my manual: 76 mpg round trip to work with the A/C off, with it set to ECON A/C ON I get 60 mpg.

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Old 06-23-2011, 08:02 PM   #7 (permalink)
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Hi Cah155, congratulations, getting an Insight these times is like hitting the lottery...
I think I was exactly in your situation some time ago...having to drive in 4th gear as in 5th the car was not able to enter lean burn for more than a couple of seconds at a time. I wanted to get good mpg that some times at night I was slowing down to 35-40 mph and driving on the highway in 4th gear in lean burn I thought that was the only way I could get 75 mpg....

And while there is a long learning curve for improvement of the efficient driving there are some pure mechanical problems that develop with our cars from time to time.

First the good news : most probably it is not high mileage engine fatigue.
That was my biggest fear when I got mine and it was doing ~53mpg . At that time I felt the car did not have any power . It was pushing 200 000 miles on the odo and I was afraid that the engine was worn out.

Mine had similar symptoms: I had to drive mostly in 4th gear as the car would not enter lean burn in 5th and often could not keep moderate speed in 5th gear without IMA assist (unless I was not going down hill )

So after finding some interesting posts here I started on the way to better mpg.

- tire pressure - 44psi and car feels better
- EGR valve replacement ( look for the herky-jerky symptoms post )
- new spark plugs (they need replacement at 105k and mine were at 196k - but looked in perfect shape)
- under body panels, mine were missing (once installed things got a little bit better at higher speeds)

- EGR plate cleaning ( huge difference, probably several horses found their way back to the engine on that day and I could start driving in 5th gear)

- new 12v battery . mine was bad from the day I bought the car and probably contributed a lot to a constant hidden charging and robbed my engine power all the time...

- grid charger. If your battery is under stress , the overnight charging may fix that and prevent the frequent recalls /charging which start when the battery weakens.

The problem with the IMA battery IMHO is that once the car starts developing some problems like for example low tire pressure and clogged EGR plate , then the balance of power needed for moving the car around and for charging the IMA battery is destroyed. The engineers at Honda calculated the engine power for maximum efficiency, but seems they did not provide any cushion for when the car performance deteriorates and did not take into account the driver reaction.

So once the engine start producing less power the driver starts adjusting his stile to get the same MPG he was getting when the car performed better. The first thing is to reduce the charge /assist events. And the better the driver gets in avoiding charge and assist the worse the IMA battery gets as it is being less charged and less exercised.

So once the engine deteriorates , the IMA battery follows. Once the battery is in bad shape enough it stars charging most of the time, and becomes more of a liability than of help...

a grid charger fixes the deficit of power and rejuvenates the IMA battery.... time will tell for how long in my case...

also other small things help, synthetic 0W-20 engine oil, correct transmission fluid, engine block heater in the winter, not using the A/C, slowing down... ( I do not drive with 35 mph in 4th any more, my car is in good shape enough to keep 75mpg with 50-55 mph on a level road now in 5th gear)

good luck !
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Old 07-03-2011, 01:47 PM   #8 (permalink)
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wow thanks for all the great help guys! Much appreciated
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