91stang

if i were to do this how much would my gas milage change? right now i'm getting about 16 mpg but wouldn't it juts go down about 1?

Black Snake

I noticed a huge difference on Gas Milage, I used to be able to fill up my tank and it would last me about a week and a half, but now with the 3.73s it barely lasts me a week. Maybe because im driving on the freeway everyday to school.

Tims 88GT

it depends on your driving, i get better milage with my 3.73 than my 2.73, now if your on the highway a lot and going 70+ then your milage will be less.

91stang

it's about 50/50 for me so there probably would be a slight change i guess? i live on campus and everything is together pretty much.

Predator

With 50/50 you will most likely notice a drop. But with 16 mpg, that seems like you are doing more city driving than freeway. A healthy 87-93 5.0 should get around 18-21 mpg with mixed freeway and city. I think the mpg estimate for the city is 15/16, so unless you're pumping in more fuel than stock there might be something a bit wrong with your car if you are doing 50/50 driving.

All this to say that the estimated 24mpg or so on freeway will probably go down to 20 or a bit less, and the 16 city might go up to 18 or so. All around if you had the 18-21 mixed milage, you'd most likely get consistant 17-18 mpg. Remeber these figures are estimates, and based off the 16mpg city (if a mustang's supposed to get 14, then with the 373 gears you'd most likely get 16-17mpg mixed).

I took all this into concideration (hopefully its pretty accurage) and decided to eventually get the 355 gears, so I get a little better freeway mileage, and with alot of roads around me being 40-50 mpg, the 373s would cut into mileage a bit too much, but the 355s would be just about right.

I've also heard it said that for all around street/track driveability/performance, the 355s are the best, but if you like a bit more acceleration and don't mind the cost of an extra mile or 2 less mpg the 373 are good, the like with the 410s.

I don't know what you have in your car, but if its all stock and you want to get gears first that's understandable, but thankfully new intake/exhaust and better ignition will increase your mileage and hp, so that's where I've started.

Kinda turned into a really long post, but I think its all pretty valid things to take into concideration when deciding final gear ratios.

91stang

it's not stock i used to get about 14 mpg stock but now i got CAI, headers, O/R pipe, and flows and it's up to 16.

i don't have a choice from 3.55's to 3.73's b/c i'm getting a spare svo and it's 3.73 rear end stock

86HOGT

The SVO rear ends are 7.5s. You're talking the 85-84 SVO right? Anyway, I got sweet mileage on the freeway with 5-speed an 2.73s, like 32MPG believe it or not. But only 12-13 in town. With the 3.73s I get 24 on the freeway and about the same in town.

91stang

no it's the SVO's after that year and those are 8.8

blkgt50

I would go with 3.55 gears. They give you the extra kick in that pants but they don't hurt the gas milage as much. I have the 3.73 in my 88 lx 5.0 (with out the MAS Air) and I get about 13 in the city. i really don't get on the hi-way to much so I don't know the milage there. In my 92 with 2.73 I was getting about 24-25 in the hi-way. so i would guess that it would drop down to about 20- 21 on the hi-way with 3.73, as long as your car is running like it should and you keep your foot out of the gas.

black89gt

after i put in the sn95 rear end in my 89, i get ****ing 160 to the tank...0_o wth man? and i definately dont feel any difference if there was to be any gears in there..and with my old rear end i got around 220 to the tank city/highway. and i had 2:73's