mustangman02232

uhhh math? dont care about math, except for the fact that when me and my buddy took his GT to the races we got 23 mpg with stock gears top down, cruise set 70-75 then on the same trip with the same settings got 21 with 4.10s, this is in a 99 GTwhich has the t45 and has the same .68 5th gear as the t5, after that he was upset he didnt get 4.30s, the autos have a .75 5th gear so youmight see an extra few tenths of a mile go down but nothing big

you will gain 1 mpg if that by going to 2.73s, and it will be a complete dog, also, the 4.0s are SOHC, not OHC like the old muscle cars

wmtheflash

It's certainly going to decrease your performance that and your speedometer is going to be way off. Just guessing that you're speedometer will read about 8 mph too low. The oddometer will rack up miles faster than it's supposed to, if you don't fix it. That will get annoying pretty fast, so then you'll purchase a $350 tuner to fix the problem.

I hope you're not planning to trade this car in any time soon. Your resale value will decline dramatically. You probably won't be able to sell it to a private party and a dealer might take it, but will charge you quite a bit to swap the gears back.

Please, don't ruin your car just to save a few bucks on gas. Here some tips:

- Find someone to car pool with a few times a week. Commuter matching services are free and I'm sure you're area has one.
- Take public transportation.
- Move closer to work.
- Drive slower. Driving 65 mph instead of 80 mph will save a lot of gas.
- Get a second vehicle that's more fuel efficient. You'll have to add this up carefully. Insurance costs and the price of the vehicle may make it hard to actually save.

Those are pretty much you're only workable options. I'd write a letter and complain to Ford. In the real world, the V6 doesn't get much better mileage than the V8, sad to say.

I believe what mustangman02232 is saying. My GT returned 24.6 mpg last night doing about 65 mph on the highway and I have an auto with 3.73's. If I were driving 75, then I'd expect about 23 mpg.

rls82959

This isn't a modification, but if it's an automatic, turn the OD off in town.
The constant shifting in and out of OD is annoying and seems to slightly decrease mpg.

my first mustang

The auto has a .71 5th gear ratio.

Glacial

1. Mobil 1, CAI 'n AA's 89 tune, running Shell Silvernetted me constant 32mpgat 65mph. Exhaust mods should be good too -- the 4.0 is choked pretty badly from the factory, and anything that reduces pumping losses will = greater efficiency = better milage. 65mph seems to be the sweet spot for mileage on the highway.
2. Lowering should be theoretically good for some gain, but you can get largely the same effect by extending the plastic airdam under the bumper.
3.Coast down hills/to stops in neutral, etc.
4.The stock grille looks pretty turbulence-inducing -- you might be able to realize some highway gains by going to billet or the like, but that's just a guess. I know people have made impressivegains by blocking off almost all of the radiator opening on their cars -- those openings create tons of drag, and the radiator usually works perfectly with 1/3 of stock openings.
5.Toss the spare and the jack and get a Slime inflator kit. 30lbs may not seem like much, but you're paying to carry it around every time you fill up.

SOHCman

Adding full duals raised my mileage up an average of 2 MPG.

Also my pony "coasts" something it wouldn't do before. Used to decelerate 400 RPM every 7-8 seconds (throttle closingdelay - emissions thing).

Also fixed the "Hesitation after long cruise - TSB). Not a single bog-down afterthey were installed!

SOHC

SPOOK R/T

My wifesauto06 Pony Pkg gets 24 mpgcity/ hwy. It has a Cai, 87 tune anda GT muffler for mods. Running the tire psi higher to 36 to 40 lbs helps a little bit. Clean air filter,mobil 1ect... oil helps also.

Trmachuno

The Mods that I no to increase MPG are(no specific order)-
1.UDP-+1-2mpg
2.CAI-+1-2
4.Tuner w/milage tune-+2-3mpg
5.Hi-flow Dual exhaust-+2mpg/Hi-Flow Single exhaust-+1mpg
6.Lighten ur car-Spare and jack out of trunk-+.0.5mpg all other weight 100lbs=+1mpg
Hope this helps

94Blk5.0

Some good points have been raised and I would go with a free flowing exhaust to begin with. Driving habits and driving environment have a lot to do with it, as mentioned. Iam able to easliy averge 25MPG in my 94 GT, mix of in town/highway driving, but have peaked at 32 honest MPG on a 60 mph interstate cruise even with 3.55's. So I would imagin if driven easy you should be able to net good mileage in stock form.

And for who ever made the correction"Muscle cars are OHC" I am assuming for mean 60's &70's most were OHV, as in one cam bumping the push rod, in turn, bumping the rocker arms, then opening the valve. Honest mistake.