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Sudden MPG drop

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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.
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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
 

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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.
 

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Discussion Starter · #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!
 

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Discussion Starter · #6 ·
Good idea Joule. I was going to try turning the wheels to check for drag, but the heat test is a lot quicker and easier. The gf is taking it on a long ride now so once she gets back will be a good time to check
 

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Discussion Starter · #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
 

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Discussion Starter · #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.
 

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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 ;)
 

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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.
 

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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).
 

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Ah yes, sorry, 1 gen. Yeah, from what I understand the 2 gen mpg marketing numbers could be a bit optimistic.
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.
 

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Discussion Starter · #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.
 

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my first two tanks clocked in at 4.9 km / L, which I don’t think is bad at all.
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.
 

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Discussion Starter · #20 ·
With gas as expensive as it is in Europe, convince the gf that slower driving = more quality time with you (assuming you are traveling together).
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 😬.
 
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