gas mileage

[Kev1990]

So I've been doing MPG checks on my 90 ACCORD recently more often then usual because its my car to stack the miles on. Anyways a few weeks back I did a 3x transmission drain and fill before the drain and fill the most I would get out of a tank is 318-325 miles no lie that's when the gas light would come on. Its been that way for atleast a year. In all honesty I am getting 402 miles per tank just above E, 442 miles to the tank exactly when the gas light comes on. First time I pushed it til gas light came on at 442 miles and it took 14.5-14.6 gallons to fill at the pump. Second tank I maxed out at 402 miles before a refill as I did not want to push my car again LOL witch was around 13-13.5 gallons on that refill

My reason for posting this is because I'm in shock of the difference and how is it possible on a automatic for this? I test my MPG's weekly normally by doing this method and have NEVER been able to reach past 325 miles without the gas light coming on and sometimes sputtering out of gas as even with 325 miles per tank I was putting the same amount of gas in.

Maintence has always been done to tho car by me but I know for a fact the MPG increase changed right after the transmission was serviced but how is this even possible? I still do all of the same driving on the same dam roads I always got 325 miles to the tank.

My recent driving habits have changed a little though with it being summer time.

I turn on the car within 60 seconds I'm moving I used to let it warm up all the way last year but I haven't done that since November of last year so that's not the big change.

Instead of doing 40 MPH speed limit I do 50 to keep it steady as I always have but I've also been keeping it at 60 in a 50 these past two months I've been doing that lol I know a little bit of speeding :P

I noticed since the drain and fills the transmission will shift earlier quicker and smoother then it was before the change like now I can get it to easily shift at 2.2k-2.4k instead of the normal 3k I can even get it to shift at 2k if I want it to without a problem.

I probably do 70% none stop moving-driving and 30% city.

I have gone through 3 tanks since the drain and fill and on my fourth all the same results the REAL question here how is it possible that's really why I'm even posting this I mean I am averaging 29-30 MPG according to these results NEW EPA ratings weren't even that high.

My other cb7s with the F22A6 will get about 350-380 miles to the tank last I checked but even the 10th anniversary edition doesn't get this kind of MPG's.

So please anyone with real theories of how this is even possible PLEASE POST UP.

Laying in bed trying to find logical reasons in my head to justify this change I forgot to mention the day I serviced the transmission I switched from Valvoline 10W30 with Purolator oil filter to Quaker State 10W30 with Napa gold oil filter. That work alone still SHOULD not justify the change even though the transmission fluid was brown and very dirty.

Forgot to mention when I first bought this car it was getting 400-440 miles to the tank but that only lasted so long lol. I remember because I lended it to a family member who did roughly 2k miles in the one week I lended it to her and she was real surprised with the kind of MPG's I was getting lol.

[wagon-r]

If the transmission was hanging up and not upshifting when it was supposed to, this could explain part of the difference. I think the gear ratios in your automatic are:
1: 2.705
2: 1.464
3: 1.028
4: 0.707

So, for example, if the transmission was staying in 3rd gear at 40-50 mph instead of shifting to 4th, this means the engine would be turning 40% faster. General rule of thumb from my days at Chrysler in the early 1980s is that every 10% change in engine speed is worth about 3% fuel economy on the highway (although only about 1.5% in city driving). So, 40% higher rpms could reduce your highway fuel economy by about 12%. 400 miles per tank times 12% = about 50 miles per tank.

Thus, if the transmission flush caused the transmission to upshift when it was hanging up before, this might explain about 40 miles of the difference in how far you can drive per tank, considering your 70% highway/30% city split.

Another possible consideration is that cold temperatures reduce your fuel economy. The air is denser (more aerodynamic drag), the tires are colder (higher tire rolling resistance), and the engine takes longer to warm up (more fuel wasted to heat up the engine block). Depending on how cold it gets where you are, I would expect a 10% to 20% decrease in fuel economy in the winter compared to the summer due to these factors. Although this is offset to some degree by air conditioning load in the summer, so the net might be a 5% to 15% drop from summer to winter.

[Kev1990]

Thanks Wagon for posting but just let me clarify all of the gears including the torque converter worked before the completely new fluid was put in and just 6 months back did one drain and fill and one about 6 months before that then once or twice early last year. I check my tire pressure weekly always kept at 32 PSI even when its been hot out like it has been recently I literally didn't get this kind of MPG til the transmission was serviced.