How do I increase gas mileage?

[Maverick3n1]

I've got a 2003 Eclipse GS with a 2.4 liter 4 cylinder engine. Stock is supposed to be 145hp however with the exhaust system it has now, it's closer to 150 or 155hp. I currently get on average of 20-22mpg (depending on if I'm freeway or street driving). Here is what I can't understand.

There is a guy that works across the street from me with this sweet 1980 Corvette. He has a 383 (350 with changed out piston kit etc..) under the hood. For those of you who don't know the number to size, he has a V8 5.9 liter (or there about) and is pushing about 420hp. So he has almost 3 times as much horsepower as me, is pulling probably a heavier car, and has more than twice the piston chamber space to fill with fuel. He gets on average, 20 mpg.

How is it that he has almost 3 times as much hp (with no turbo) than myself, over 2 times as much space per engine revolution to fill with fuel/air mixture, and he still gets almost exactly the same fuel economy as me. I would think he should be getting half the fuel economy I get. I mean I can understand him getting more hp with that large engine, but the drawback is supposed to be worse gas mileage. There are Honda Civics that get what I get for hp and yet get 38mpg...

What kind of mods can I do to dramatically improve my gas mileage without hurting my hp? With gas prices skyrocketing, spending a grand on the engine to improve gas mileage might be worth it in the long run. A turbo will obviously increase performance a lot, but it won't solve the gas mileage issue. I don't race the car, so I don't need ungodly hp. I just like to have the get up and go for when I need it for passing and such. The fuel economy however is a big issue.

Any help would be appreciated!

[SkiNutJones]

What I would do. It might not help a bunch, but it will do something. Run a good quality oil, I use Mobil1. Also, if its not already done change up to a K&N air filter. Again this might not help much, but its the best I can do!

[Rulez]

Change the oil to a thinner mix, get an intake, and back the screw on the bottom of the MAS out about 3 turns. That will help a lot.

[Maverick3n1]

What does the screw control on the MAS? Is it something that's fine tuned? If I back it out too much or screw it in too much, can I expect the engine to run poorly? Never heard about adjusting a screw on the MAS.. Let me know =) Thanks!

[Rulez]

To be honest, I dont really know how it works. Somehow, backing that screw out allows more air to pass through the MAS that the ECU doesnt compensate for, which gives a little bit of power and better fuel economy. All it is doing it leaning out the car a bit. The actual science of it...I dont know.

[Igovert500]

Oil and K&N air filter(plus you can clean them, so you don't have to waste money replacing them) as was said. Also, I wouldn't screw with the MAS too much, as leaning out your car can lead to knock and destroy your engine. i doubt that fooling with the screw would lean it out too much to a dangerous point, but just in general, its better to be safer then sorry.
Also this might be too obvious, but shift at lower rpms. That guy is only getting that mpg if he is shifting really really low. So try doing the same, its easier with a manual, but if you have an automatic, don't give it too much gas, just accelerate slower so that it will shift quicker rather then prolonging the shift.
And the best solution...use public transportation(only half serious) I use the off campus buses my college provides to do the 8 mile round trip 2 my campus 2 times a day. It keeps the $40 refills a little more spread out. Good luck

[Maverick3n1]

The best gas mileage I ever got, I watched so that I'd never go over 3k rpm, and even then, I only got like 22.5mpg...

[Igovert500]

Well that sounds about right for street driving. But if you are going all highway, you should get up to 30mpg. When you are on the highway driving, what speeds do you drive at, and do you use cruise control. Because 30mpg, is based on normal speeds, 55mph-70mph, if you're like me, a leisurely highway drive consists of speeds 95+ and I hardly ever use cc, so obviously I don't get as good gas mileage.

[Maverick3n1]

Lol.. I live in So Cal.. no such thing as using cruise control out here.. Too much stop and go...

As I said before, I'm just upset that on normal street driving, the guy with twice the size engine as me gets the same gas mileage as me just about... If I'm not pushing it, I should be able to get much better mileage than him.. but he gets 20 miles to the gallon with almost a 6 liter V8 under the hood...

[Ace$nyper]

another thing to do is lighter wheels and tires really pick up gasmilage. Start taking shit off car A/C rear seats thats messy but works.

[Maverick3n1]

hehe actually the body is the heavy part.. the rear seats only weight about 5 pounds.. I've taken them out before. They are just padding with some cloth over them. They are mounted right to the floorboards of the car, and only have some thin wires holding their form as when they are connected to the floorboards it holds their form.

[Igovert500]

Yeah Ace good point, lightening anything that rotates between the crank and the wheels helps save some hp that would be gone due to parasitic losses. If you lighten things such as flywheel, driveshaft, wheels/tire combos, you can save alot of weight where it matters the most. (Stay away from chrome rims) This puts less strain on the engine to turn it, so you will pick up some hp and get better gas mileage. Losing weight in rotational mass is much more beneficial than normal weight reduction.

[SkiNutJones]

Which screw on the MAS should you loosen I took it off and all thats on the bottom of it is a hole filled with silicon or something. Do any of you have a Picture of it or something? thanks

[SkiNutJones]

I figured it out and made the adjustment. What a difference. More power and smoother running.

[Rulez]

Yeah, its covered in silicon. You have to scrape it off.