What kinda MPG can I expect?

[PAYNEinjc85]

I recently traded my POS 92 S10 in to my buddy for a 95 Cutlass Ciera. It has the 3100 SFI. So what kind of fuel economy should I expect? Most places online say up to 26 MPG but the previous owner swears it got better. My dad has a 2000 Grand Prix Se with the 3100 and gets right around 30 MPG even though it's only supposed to get 27-28. I'm gonna be using the car as a gas saver if it does substantially better than my 96 4.3 S10 which gets 23-24 with highway and city driving. The same sites that say the Oldsmobile gets 26 also claims my truck should only get 22 so I'm hoping I can get 28-30. doesnt the older 3100 equipped cars have a lower gear ratio than the late model 3100 cars? Maybe thats why they possibly get better than the older 3100 SFI? Thanks

[carbon]

My 3400 Grand Am GT will get around 24-26 in the summer if I'm nice to it, mostly highway driving/commuting... and it has the 3.29 final in it. The EPA rating is 18/27, but in the winter here in MN it goes to crap and drops to around 20-22 and in the summer if I use the cruise control set at 65MPH and no A/C I can get near 30MPG...

I wouldn't count on 28-30 unless you pick up some hypermiling techniques... with an EPA rating of 17/26, I wouldn't guess you have a lower (technically "higher") gear ratio either. The 3400 and later (2000+) large port 3100 are more efficient than the 90s small port 3100.

An easy approximate way to check your diff ratio is to drive 60MPH and if your hanging right around 1800RPM (70MPH@2050RPM) you're rockin' the 3.29 in your 4T60e. If you're RPMs are lower then you've got a "higher", more economy friendly diff, and I know the RPMs won't be higher, unless your TCC isn't working, because they only ever put a "lower" 3.43 ratio in the W-body 3.4DOHC cars.

Edit - I am assuming the Ciera has a tachometer... it may not, which makes my test pointless.

Edit 2 - I looked up a replacement trans on Rock Auto for a 95 Cutlass Ciera and it shows a 3.33 final drive. (3.29/3.33 is a difference in earlier and later coarse/fine pitch gear design) and your car is less than 100lbs lighter than mine.

[robertisaar]

http://www.fuelly.com/driver/robertisaar/monte-carlo

for what it's worth, that has my fuel logs for 2012 in it.... the monte is noticably heavier than a ciera, but also more aerodynamic, so it may work out the same in the end.

[carbon]

O_O

You had to have been workin' for it, lying about the city/highway split or you have a 100mile, traffic free commute.

[robertisaar]

no, city/highway % is about right. i live ~30 miles from anything that isn't a 55MPH road for stretches less than 1 mile. sometimes i spend quite some time/distance in-town, but not often.

those numbers were nothing special, just putting my foot on the throttle to maintain 55 and stopping when i needed to. no hypermiling or cardboard body parts/etc. no comment as to how much the calibration has been changed from factory specs, i'm sure it was continuously changing through a lot of it. kind of bummed about trips 12 and 18 though, i was so close to the magical 500 mile mark, but the guage was showing empty and not moving. after filling up, it looks like i had between 1.5 and 3 gallons left in the tank.

[robertisaar]

more FWIW info:

95 ciera is showing a 3.33 final drive, but a 37/33 chainset, causing a 2.97 actual gearing.
00 GP 3100 is showing 3.05 final drive and 35/35 chainset, so 3.05 final.
95 MC is 3.33 with 35/35, so 3.33 final.
00 MC 3400 is showing 2.86 final drive and 35/35 chainset.

[carbon]

2.84 and 2.97 definitely help...

I wasn't really accusing you of lying... just surprised you were getting that good.

I have never been impressed with the GAGT... my 88 Fiero GT with a 2.8 and no overdrive can almost match it on the highway... sigh.

[robertisaar]

i tend to very easily beat EPA estimates in everything i drive..... except for this stupid 2.3/5 speed ranger, hitting the original EPA highway rating seems to be impossible in its current state doing the exact same route as the monte. functional O2 sensor + functional EGR + correct trans oil would probably get it there and beyond.

[19Cutlass94]

When my car was stock, it was getting. Mid to low 30's. Fairly consistently. Of course this was driving like grandma and no faster than 65mph on the highway. If everything is in working order, you can get high 28's. All depends on how you drive it.


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[pocket-rocket]

i tend to very easily beat EPA estimates in everything i drive..... except for this stupid 2.3/5 speed ranger, hitting the original EPA highway rating seems to be impossible in its current state doing the exact same route as the monte. functional O2 sensor + functional EGR + correct trans oil would probably get it there and beyond.

ATF, though I'm rocking Penzoil Synchromesh in mine. I rock ~31MPG in mine with 3.73s on the highway as long as it's fairly flat and I keep it at 70 (though 70 indicated is 65 in reality) or under. Any more and it drops. The largest improvement was my tonneau cover. It also doesn't get blown around from cross drafts as bad after installing it.

/threadjack

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[robertisaar]

i have two MPG advantages over yours, i have the 3.45 gears and i rarely go anywhere that allows above 55 in this truck..... and it still just failbusses its way to MAYBE 25.