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Sudden MPG drop

3K views 36 replies 8 participants last post by  bobgg 
#1 ·
Hey everyone,

I recently changed my CVT fluid (using the proper Honda fluid) and serpentine belt and afterwards I’m seeing a 4 - 5 MPG drop (from 48 to 43/44). This is over the course of two tanks.

I made a mistake refilling the CVT, underfilling it about a quart. When I started the car to drive it and warm it up, I could hear some not too loud screeching from the engine bay, so I stopped right away. All in all I drove maybe 500m. I realized and corrected my mistake, which resolved the sound and driving feels normal. It’s slow to creep in D from standstill, but maybe it was like that before, I’m not sure.

I’m a little worried about the CVT though. Did I damage it causing the loss in MPG? Could it be caused by the new serpentine? Could removing the wheel and reattaching it cause the wheel to drag? Would love to hear what you all think.
 
#2 ·
Do a recalibration of the CVT.

Take the car on a flat road. Turn off all the accessories(lights, stereo, anything).
Drive until you reach 59km/h(do the conversion for Miles/h).....and the take tour foot off from the accelerator pedal, and let the car crawl until reaches 7km/h.
You save to find a road that gives you this conditions.

This way you gonna realigne the CVT.

You will find this procedure in the service manual also.

Good luck

Inviato dal mio Mi A2 utilizzando Tapatalk
 
#3 ·
I'm not well versed with the CVT, but the Insight is very sensitive to cold weather. Catadarius may well be correct, but since the MPG dropped over the course of two tanks it may be because of weather getting colder. Just thinking out loud. Good luck with your car.
 
#4 ·
Alright I’ll try the recalibration later today. The metric won’t be a problem, I’m in the Netherlands;). I’ll also do a check on the tire pressure and just now drained half a liter of oil which the selling company overfilled. Could a faulty calibration of the cvt cause this loss in efficiency?

As for the weather, these two tanks were actually driven in warmer weather than the previous ones. I only have the car for a month or so, so maybe I should also not put two much weight on the mileage of the first two tanks as compared to my second two. I was just a little worried I messed something up in the first month of owning this car. We’ll see!
 
#8 ·
So no brake drag, but the tires were definitely underinflated. The right front one was around 1.8 bar or 26 psi. I upped them all to 2.8 bar or 40 psi now. Did a short test drive myself in start/stop traffic with a speedlimit of 50km/h and managed over 20km/l or 47 mpg. Tomorrow I’ll take a trip on the highway and see what it does there, but so far it’s looking good. I’ll need to keep an eye of the tire pressure though. It should drop out of nowhere I suppose.

Oh I also attempted the recalibration but I have no idea if that worked. I’m guessing it doesn’t tell you it recalibrated
 
#9 · (Edited)
Update after the highway trip, I averaged 21 km/L or around 50 mpg including some inner city driving at highway traffic jams. Total distance was around 70km. While cruising on the highway at 90-100 km/h, I did 25km/L or 58 mpg. All of this is according to the MID. I’m concluding that the cause was low tire pressure, but I’m still unsure why the pressure dropped. I’ll just check regularly if the pressure stays up now, but I’m marking this down as resolved.

All the people getting 60+ mpg, I’m guessing that’s driving mostly on 60-80 km/h roads? I would love to hit that as a trip average, but my route might not allow it.
 
#10 ·
All the people getting 60+ mpg, I’m guessing that’s driving mostly on 60-80 km/h roads? I would love to hit that as a trip average, but my route might not allow it.
Yup, you nailed it there. The marketing spec of 4-5L/100km average consumption is a fairy tale. Yes, on a highway w/o head wind, no A/C, going with a steady snail semi-truck speed of 80-90km/h you will manage 5ish L/100km (as calculated at the pump after refueling, The display is always way optimistic with at least 10% too good fuel consumption). But day to day mixed city/highway, forget it. 7.5-8L/100km is normal unless you are being REALLY vigilant and manage to minimize stopping and accelerating to land at about 7L/100km. Pure city driving is 9-10L/100km. It is not the matter of idling in traffic jams even, but simply having to stop and accelerate again. It is still 1300kg to move around. One cannot fool physics, no matter what the green ecomentalists say ;)
 
#11 · (Edited)
I couldn’t disagree with gandalf more. Right now with a dead IMA pack in an Insight I just put back on the road I am getting about 6,1 liters/100 Km, about 46+ mpg and that’s with no belly pan and no sideskirts driving mostly secondary roads in stop and go traffic. In my well-sorted Insight I typically get 5.4 L/100km or about 52 mpg. In summer I routinely get about 4.7 L/100km or about 60 mpg in mixed city/ highway driving and both of those cars are CVTs. I guess we use bigger liters on this side of the pond.

I have to clarify — my gallons are US, not imperial.
 
#14 ·
So, to achieve those mpg numbers I use Honda spark plugs, RE 92 tires inflated to 45 PSI, Scott K’s custom aluminum belly pan, a clean EGR plate, a good alignment and no dragging brakes and avoid jackrabit starts and panic stops. I try to avoid stopping altogether. By that I mean I will regen brake up to stop light as much as possible before actually applying the brakes. I coast whenever possible and I am not above following a bus or semitruck (but not too closely).
 
#16 · (Edited)
Gen2 is 50% heavier than gen1, 1300kg vs 800kg and has over 10% worse power-to-weight ratio 77 vs 86 hp/tonne and is 7cm higher.
Added weight, more under-powered, more aerodynamic drag. None of this improves mileage, really.
That said, Gen1 specs with 83! MPG
does not look all that realistic.
And then gen2 with 64 MPG
please... who are you kidding? (Remark directed at those writing the specs, not you @Joule ;))
And converted to US gallons
69 vs 53 MPG Gen1 and Gen2 respectively.
 
#17 ·
I’m curious how it will develop. Most of my rides are long (60 - 100 km) and the MID often puts me around 4.5 - 4.8 L / 100 km (49 - 52 mpg), and this is in fairly cold weather. I’m hoping it to be a bit better in the summer even. I’m fairly patient though and don’t mind hanging around in the slow lane, coasting up to each light and avoiding the use of the brake pads. The gf is a little less patient though, so it’ll be tricky to measure at the pump, but my first two tanks clocked in at 4.9 km / L, which I don’t think is bad at all.
 
#20 ·
Sounds like a smart plan ;). We only sporadically travel together though, but I think it’s fine the way it is. If we can keep it on or under 5L / 100km, I’m very happy.


That is a great result if you ask me. I am running 40psi in my tires, maybe I'll try 45psi as well. Recommended pressure is ridiculously low 33psi, as printed on a sticker on the door frame. I cannot believe that is right, since even visually it looks underinflated on the car.
I indeed think the 33 might be a bit under, but 45 to me feels like it would really be over. I know some others on the forums here run it, but I’m running 40 now. It already feels like having to do an evasive maneuver in the rain might be risky, so I’m actually considering lowering it a bit and seeing the impact on my mpg. Not sure how the weather is in Poland, but I wouldn’t like 45 psi on frozen winter roads myself 😬.
 
#22 ·
Regarding MPG/KPL, my 01 CVT used to clock in over 50 most of the time with: A) careful but not pedantically so driving working for me; B) the topography of my landscape is pretty hilly which is a mixed bag; C) my IMA was weak, I had no belly pan, and didn't monitor my tire pressures carefully.

When I had 2 different people use the car for many months at a time, driving it without any significant understanding or concern for the details of how to maximize efficiency, the MPG tended to range from about 43 to 48 per tank. I personally occasionally slipped down into that range, usually when hurrying (maintaining high average speeds) on long trips that included some significant hill-climbing. This

While I understand the principle of higher tire pressure being good for MPG, my own experience has been that above some reasonable number (depends on the design of the tires and the weight of the car), the returns are diminishing. In my insight, I tended to run in the high 30s and didn't see any measureable increase when I pushed it over 40. When I might have let 1 or more tires drop down into the low 20s, I do believe I noticed.

I live in the mountains of the southern end of the Rockies (NM) where snow and ice have become fairly intermittent over the last two decades, but am still fairly aware of the need for decent traction when those conditions emerge and do find that higher pressures (over mid-30s) on that care yielded some noticeable loss of traction. I have a particularly icy, shaded, windey hill which on occasion becomes wicked-treacherous and the smallest difference can matter... I have deliberately dropped the pressure in my insight to about 20 to be able to navigate those conditions with a little more control and it the extra softness and traction area definitely helped!

My Chevy Volt is quite a bit heavier and I find the difference both in MPG and in traction to be less dependent on tire inflation, but then I am running Bridgestone Run-Flats which may not suffer is much with lower pressure given their very stiff sidewalls? The Volt has much more precise instantaneous instrumentation... especially with My Green Volt monitoring the current draw and speed (and therefore miles/kWh) and I find that under similar conditions/terrain that driving style significantly dominates mpg, including acceleration/deceleration and speeds. Some of my best efficiency actually comes from climbing a fairly steep 9 mile hill from my home at 40-50 mph, driving a few miles around a fairly flat mesa-top townscape at under 25 mph and then back home (9 more miles with a 2000 ft drop) at 40-60mph.

When I commuted the same trip in my Insight, I didn't do quite as well, probably because the downhill run was pretty much 15 minutes of "idle" without a big enough battery to return more than a little of the energy from the climb through regenerative braking. Occasionally I would "hypermile" this route, but the power-steering/brakes without engine were problematic for comfort/safety. I suspect I could have done a great deal better with an MT on these routes.

Previous to my Insight I hypermiled/coasted my 84 CRX-HF the same commute up to 70mpg per tank. I don't think I ever broke 65mpg on a tank with the insight, but beat the CRX on all other routes.
 
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#23 ·
@sasmyth how many miles do you get per kWh in your Volt for the round trip you described? And what is the consumption rate for just the climb?
 
#24 ·
I don't record these (outside my faulty anecdotal memory) but a reasonable estimate is that I probably arrive home with about 5kWh/10kWh useable from a nominal 25mile RT (including some "around town". Under the best conditions, the climb consumes more than that, I regen about 1kWh on the return... so about .5kWh/mile...

The run from my home to my (former) workplace and/or the downtown location of the small mountain town is nominally about 11 miles with the first and last mile being only slightly uphill. I hit the top of the hill with more than the 40% retained by mountain mode, showing 4 or 5 (of 10) bars on the dash... depending on circumstances, I may or may not trigger mountain mode before heading back downhill...

That first/last mile on the mesa-top is too flat to coast the whole way back down, but the consumption is very limited for that short run... sometimes that is when mountain mode kicks in if I allow it and then the minimum .10 gallon gets burned... but I avoid that naturally.

Your question has me wanting to track those three (six) legs more specifically. Unfortunately here in mid-winter I never (as of this year) get a clean run without triggering the ICE in some combination of 1) almost immediately; 2) early in the climb; 3) the duration of the climb; If I (or the cold-mode) run the ICE the whole climb, it still slips behind with some high RPMs on the steep parts.

I'm looking into the battery-heating system to see if that is failing (intermittently) because the cell-by-cell performance monitored during and after use/charge doesn't show any obvious issues.
 
#25 ·
Man, I really like this car. I was finally able to take it on a longer drive, by myself, going to work and back. All in all adds up to a little over 190 km and, this time, included going into the city to pick something up (which took half an hour or so) and some highway traffic jams. It did the entire thing in 4.3 L / 100 km (54-55 MPG) which is the best trip yet. We’ll have to see if the MID is vastly underestimating, but do far it seems pretty accurate.

Given that this was all through 0 - 1 degrees C, it’s absolutely amazing to me. I’m curious how much a (partial) grill block would help, because I had the feeling fuel efficiency kept going up even 30 - 40 minutes into the trip. I can’t wait until it’s nice summer weather again to see how it behaves then.

Speedometer Odometer Trip computer Gauge Car
 
#28 ·
I’m curious how much a (partial) grill block would help
Most likely nothing, or cause overheating when there is a need for good airflow through the radiator, unless your thermostat is malfunctioning and opening too early or stuck open. The cooling system is designed to keep the coolant at the optimal operating temperature regardless of weather. If it is cold, the thermostat won't open and there won't be any coolant circulating through the rad anyway.
 
#29 ·
Damn, mine is almost always about 10% too optimistic. Even when I consistently filled up to the brim until I actually saw fuel in the inlet to rule out any error due to pump cut-off.
Same thing when I ran the distance over 3 or 4 tanks (some 1500kms) to average out pump cut-off.
 
#27 ·
My experience for over a decade of checking this nearly every fill up was that it was very accurate, I chalked up discrepancies mostly to differences on just how/when I cut off the pump...

Even though it has been decades since it made sense (to me) to "top up the tank to the next round number" as my father always did "back in the day" I still find myself dropping in another fraction of a liter (.07?) now and then. I'd guess that the fill-tube is likely to hold a larger fraction of a liter if you push it.

The pump auto-cutoff sensors are likely to vary from pump to pump, even time to time?

I'm very impressed with the ability of modern computer-controlled vehicles to measure fuel consumption on the fly so accurately... it makes sense when you think of how precise the fuel-delivery via computer-injection needs to be.

Glad you are enjoying your Insight. I'm a little jealous... having flashbacks to my first year of ownership!
 
#31 ·
If you have an engine that is designed to be water-cooled, no amount of cold air around it will have any significant impact on its operating temperature. Higher under-hood temps on the other hand, will cause all sorts of mayhem especially to all plastic and rubber elements which will deteriorate much quicker, become brittle and crack. Typically connectors, cable insulation, rubber vacuum lines. The exhaust manifold has a heat-shield in order to prevent frying everything around it. Higher intake air temp will rob the power. Yes, less fuel can be burnt in hotter air because the air is less dense, but that robs the available power. Any additional mileage gains from taping up the grill, and other openings for that matter, if at all come from reduced aerodynamic drag.
If one wants to reduce cold starts to reduce engine wear, then there are dedicated engine heating systems, such as webasto that accomplish that. However, that is more relevant during really extreme temps like -20C or so. My dad once owned a car equipped with an engine heater (that warms up the coolant and oil) that was powered from the standard 240V power grid but in the end, the cost of increased electrical power consumption outweighed any savings in fuel consumption. Tested over a period of two months with temps oscilating around +/-3 degrees C.
 
#32 ·
If the air temp around the engine has no impact on operating temp, then what causes cars to run less efficient in winter? Surely it’s a given that warm (not hot) weather is good for fuel efficiency. So if I were to modify the intakes such that the conditions under the hood are like they would be in summer, even though outside the engine bay it’s cold winter weather, I think you could expect an increase in mpg. The reduced drag is actually a good point and an added bonus. I suppose in colder climates there’s no need for the additional air vents, which might be there to allow the car to work in hot climates or under heavy loads.
 
#33 ·
Greate man, I also drive insight gen 2. From flanders. Interesting to know more about your MPG. Mine is about 5.8 to 5.9 and that's because I have all season tires on which really screw up the millage. BTW, Do you know what are you gonna do if the IMA battery is gonna die? Do you know a good place in NL to fix that?
 
#34 ·
Hey Bob, nice to hear someone else fairly close driving one. I actually also have all season tires, so it can't just be that. What pressure are you running your tires at? I do have the benefit of almost never having short drives. The vast majority of my trips are 70+ km, which really helps push the average consumption down. The way I drive, which is really light on the throttle, it looks like it can do 4L/100km on the highway. Sometimes even 3.5.

As far as the IMA goes, I really don't know yet. I'm still trying to get my cheap knockoff diagnostics tool to work, so I can hopefully learn a bit about how good/bad my pack is. Depending on that I will do nothing yet, grid charge it, run a discharge/charge cycle or explore replacement options. I've heard that the replacement packs are kind of crappy though, as they use mostly cheap NiMH cells. I was also thinking of building my own sticks with better cells or exploring a Li-Ion conversion, but those are all pretty major projects that I might also very well never start on. We'll see what I end up doing :)
 
#35 ·
That's an impressive fuel economy. I don't know what could be the case with mine. I had a rear dragging brake with a faulty brake caliper which definitely impacted my millage. Just the entire caliper last week. Took me about 1 hour but seems like the problem is solved. Tomorrow I'm gonna drive it all the way till French Alps so That's the best time to test the millage and check if there is any improvements (which for sure there will be but not sure how much). If I go light on the throttle, I hope I can get somewhere about 4L/100km and I'll look like a turtle on the road. How fast are you normally driving it?

This ODB would work pretty fine for the battery test. A bit pricy though:
I recently checked this company in NL. They claim they use a technology that detects only the defect cells and they only replace those cells. That's why they can fix it for a cheap(er) price. So perhaps worth looking at it.
 
#36 ·
Oh yeah a dragging brake will massively impact your efficiency. Also check your tire pressure before you go on your trip and make sure it's good. I typically drive around 95 - 105 km/h on the speedometer of the car, so I should average around 100.

Thanks for the scan tool! I might look into it if I really can't get mine to work. I would really love to be able to use the HONDA HDS and be able to look at everything, but I might have to settle.

The company for the battery also looks interesting. Although I always feel like the 'reconditioning' they do is probably just one or more discharge/recharge cycles to rejuvenate a little. Sounds like it would be with the 6 month warranty they give. Still might be a nice source for their new batteries or perhaps to get sticks. I'm pretty confident I'd be able to identify and replace those on my own.

At any rate have a good time in the Alps! I hope you have clear skies and nice views.
 
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