I'm getting flamed for this but it's what I want and a big goal I'd like to achieve so....


I have a 65 mustang that's going to be getting a ls1 and t56 swap. As the title states, 30 mpg highway is the goal and I don't see why I couldnt. My buddy has a c5 z06 and got 28 while going 80mph.

Specs:
65 stang coupe round 2800 lbs
3.25 gear
T56 trans

Engine rpm should be around 1300 at 70. Ideas? Suggestions?

 

Buy a hyundai elantra and get 50+mpg?



What does your 65 weigh?

 

I don't see why you wouldn't get 30 highway with that setup. But just remember that all the guys on here talking about 30 MPG's consistently are getting it basically 100% highway, when you mix in city it will be a lot lower (22-25ish depending on a lot of different variables).

 

My '85 302 Mustang uses EEC-IV and gets 24.5 highway (16-17 city) with a Tremec TKO600 drag ratio transmission and 3.27 gears in the 8.8" rear. It weighs just over 3k with me in the seat and has all the creature comforts. I've never tried to get better fuel mileage than that... that's just what I got with a mildly built 302 running a good tune and driving it using a light enough foot. If you trim your curb weight a little more, go with that 3.25 gear, tune it well, and drive responsibly I think it could be done. I think 30 mpg would be tough, but you could pull it off. Make sure you share your findings once you do.

 

weight....loose it..

 

Looks like I'm about 300 lbs lighter then a c5

 

You should hit 30mpg highway pretty easily.

 

A lot of that will have to do with The tune and your personal driving habits. You maybe lighter then a z06 but transmission is different. Your gear set is wider then a 3.42/MN12 combo the z06 gets. Sometimes having a quicker ratio trans helps get you going but then you would skip gears and get to 6th as quick as possible. Keep the rpms below in any gear, and no pressing down of the throttle more then is needed to accelerate.

When it comes to the tune, people run whats called a lean tune where your in a situation of part throttle on the engine runs a lean A/F around 15-17 A/F which is fine as when you go WOT it will drop down to a 12.8 range.

One thing that could hurt is your not as aerodynamic as a z06 and that does make a difference when driving at freeway speeds. Should not hurt you too much but could effect the result.

So if it where me, I would have the mind set of quick clutch drop, below 2k, then a 1 to 4 shift, and depending on where I am 4 to 5 or 4 to 6. All doing this at a part throttle and then on the freeway keeping it 65-75 consistantly.

The motor may lug trying to keep it in 6th, in town and thats why the 3.25 and 0.50 6th may be too low (numerically) and you may start lugging/surging. If you keep it a stock cam, you should be fine but anything upgraded would/should need more gearing for the take off and last gear.

 

keep the gear low, dont do TOO much to the motor and dont drive the **** out of it and you should easily get 30mpgs.....

 

Your aerodynamics are dismal and my '66, 289 that
turned about 2000 at 60MPH never got better than
20 highway. If you want MPG an EGR system would
help some if you could tune it right. There's also a happy
place for closed loop cruising O2 pivot voltage, which
you'd have to find by looking for min MAP on level
ground.

I doubt you'll see that 30MPG unless your commute
is downhill both ways.

 

Comparing a carbed 289 to a tuned fuel Injected motor is night and day. I see about 9-10 in town now. May be little rich but runs well.

I'd love to find a wrecked car and use what I can instead of doing it piece at a time but don't think funds will allow. I'm thinking engine and trans for 15-1800 then another grand for misc stuff. There's a trans locally on c list for 700 but we'll see.

 

you can hit 30. but remember there is allot more then gearing that makes a difference in mpg's. just changing the way you drive can save 30%!! same car with just an attitude change and driving with elevator music instead of pantera can get you 7-10 mpg. gas savers.org has lots of helpful tips. i followed their advice and got my del sol up to 44mpg.

 

2.73 gears

 

30 is not hard to get apparently. I took my SS on it's first highway trip last week and got 28 there and 31 back. I've got the 4l60e runnin 3.23 gears

 

The only thing going against you is aerodynamics as mentioned but its not like a truck or anything, its still a little sports car so as long as your not cruising at 80+ I think you'll be ok. Just get a good flowing exhaust and headers and intake and a great tuner and you should be able to get that or very close to that in that light weight little car.

 

Think about lowering it a bit, and adding a front airdam that's pretty close to the ground. That will most likely help with the aero, which IMO is going to be your biggest obstacle in your mpg goal.

I actually want to put an airdam on my Formula, next time I hit the junkyard I want to look around and see if I can find one that fits the contours of the front end, and will sit behind the factory airdam that funnels air to the radiator.

I figure since the stocker is flat, one that wraps around will help with aero by funelling air out from under the nose instead of letting it go under the car.

 

Also keep your rotating weight low, such as carbon drive shaft, your diff, your flywheel, a good balancer like ati and get it in an under driven as well and use as much fiberglass body panels as possible since your aero is well not the most favorable but ut can be streamlined some. And skinny tires as they are rolling resistance and keep in mind your brakes, and light weight wheels as well. It's only money we are talking about ya know.

 

I have heard mixing a little bit of nail polish remover in with gasoline will net you big mpg gains. Do this at your own risk though, and look into it further.

 

should be able to get 30!

 

Well, did you get 30? LOL