just got back from a 800 mile round trip averaged 28 mpg going there, was speeding on the way back and averaged 25 so im super happy with my lt1 of course i luv 6th gear though!

 

Maybe it's because I have an auto or something but I cannot believe you are getting 28 MPG!! I've got a freshly rebuilt motor and kept it under 3500 rpms for the first 150+ miles and still only got about 21 barely. Probably do about 30 miles hwy combined each day.

Now after the break in I did a lot of WOT and got about 14mpg .

 

On a long cross country drive my LT1 Formula M6 averaged around 27.5mpgs.. a couple tanks were in the 28 range and one was just about 29mpg.

 

Thanks for all the suggestions. Many are a little over the top for me, but It's a good conversation. When I get headers, I'll surely get a tune. I'll most likely get a mail order canned tune from PCMforless or something.

I used to have a 99 turbo v6 camaro with 465rwhp 510rwtq. I had HPtuners and alot of custom one-off parts. The car was very fast, and a blast to drive, but it was extremely difficult to maintain, and extremely expensive. I'm not gonna get into anything more than bolt on mods until I own my own home with a garage and I have money to build another car. The main reason I drive an LT1 car is because I'm spending most of my disposable income crushing credit debt. That is NOT the reason I'm shooting for better MPG though. I just think it would be fun for bragging rights.

Most of my coworkers drive new BMW's, STI's and other hi-po cars. I want to have a car that handles as well as they do(done), accelerates as fast as they do, and is just as efficient as them for 1/10 the price.

On to the good stuff: I just filled up and calculated my latest mileage. From mobile AL to Meridian MS, there is a 300ft elevation change. I went uphill alittle. I drove an averave of 62mph, and I got 28.5mpg. Half the route is 55mph, and the other half is 65mph speed limits.

From now on, I'm going to only use the same two gas stations on either end of my trip, to minimize innaccuracy from the pumps. My first "mod" will be washing and waxing the car for a little more aerodynamic efficiency, and some weight reduction. I'm gonna clean out the entire car. I've prolly got 40lbs of stuff in the trunk.

 

someone mentioned that your running flowmaster, when i took out mine and replaced it with a hooker aerochamber I gained 1mpg. Which after 10, 15 fill ups paid for the muffler replacement.
Next, a pcm tune will help out your mpg's, id say another 1mpg gain over stock considering how rich the stock tune is.
third, headers would help out a little bit because the engine will breath better and more efficiently. Also providing you some hp gains too.
Four, make sure the fuel filter, plugs, wires, o2's, opti, etc are all in tip top shape. Any one of these can hurt mpgs bad.
Five, make sure tire pressure is at 36 or so. Since you car is lowered you can adjust the camber and caster to a more race style specs which will help out too. A alinement(sp) can adjust those things. Get your tires balanced every 4-5k to make sure they are perfect.
six, weight- get some lightweight carpet and rip out all the insulation in the interior. Spare and jack, if your going to buy new rims in the future or can sell you ones for some light weight aluminum ones. Rotational mass makes a big difference on mpgs. I know their not going to be cheap but you can find some that weight between 18 and 22 pounds. A tublar k member and upper and lower a arms.
well about all i can think of, good luck

 

I never thought of just ditching my muffler and keeping the rest of my catback. That would be cheap and effective.

I've recently replaced the air filter, fuel filter, rear gear oil and trans fluid with hi-perf synthetic stuff. I also seafoamed the car recently. I don't know how old the spark plugs or wires are, but they have been replaced before.

I have opted to keep my stock salad shooters because I know they are fairly light. I keep my tires at 33psi, I'll up them to 36 and try it out.

I just got a performance alignment done last week.
-1.0* camber
5.0* caster
o.0* toe

That should give me alittle less rolling resistance, and it gives me better grip in turns.

 

my car was right around that mark when I ran it with full exhaust/throttle body/ud pulley/ignition box/3.73's. My mileage went down a bit when the car broke a valvespring unbeknowst to me though. Still ran great!

 

On my last trip a month ago I got 31 MPG. I was so surprised.

I just put my tires at 41-42 psi (rated for 40) and drove at 4-5 over the limit 69-70 MPHish on cruise control the whole way.

And I have an A4 , so a whole lot of it is how you drive, I just sat back and relaxed instead of driving faster and having to be super alert for 5 hrs. Less chance of an accident too. Plus I've got a flowmaster so I doubt it hurts MPG that much.

 

skinnier and shorter tires all around will help mileage, but hurt handling...

headers will help. A cam designed right can improve gas mileage and increase power up to the stock redline. Increase the static compression ratio will help get a more complete burn and waste less fuel. Cleaned up cylinder heads will reduce pumping losses. A longer runner intake manifold. Wideband tune. All the above should help improve torque and reduce surging or lugging at LOW RPM where you will get the highest mileage.

My truck seems to get the best mileage between 1500-2000. But with the gears and tires that I have, that's 60-80mph

do you have an aluminum driveshaft yet? aluminum flywheel? what clutch? cross drilled and/or slotted rotors might weigh less. gun-drilled axles.

Obviously skipping gears not needed and getting into the highest gear as soon as you can help mileage.

 

??? i'm pretty sure the speedo/odometer is through the rear end? could be wrong just deducing the fact that my speedo mph rises when i burn the tires... or play in the snow...

 

I've programmed my LT1 many times. There are only a couple of things to do that will help mpg. One is leaning out the open loop tune, which is what the car uses before it warms up and enters closed loop. This will help a good amount if you make a lot of short trips with the car. The other is leaning out the WOT tuning, which is rich from the factory.

Once the car enters closed loop, it will target 14.7 a/f, so there is nothing you can do with the tune.

Dan

 

I believe it's on the transmission output shaft. That's why you have to make adjustments in the computer if you change your rear gears.

 

Cant you detune the car to run on 83 octane gas?
That would save a ton of money by its self, if you are looking to save money and not the world.

 

Yes, you could reduce your timing across the board in the spark table. You would lose power, but if you're not interested in power, then it might be o.k.

Dan

 

When you do things like that you have to also look at your cost per mile. If you de-tune for cheap gas, but lose enough MPG in the process, it can either be the same or *more* expensive per mile compared to a better tune with quality gas.