So Areodynamics?
 

What are the most effective areo mods that people do to their cars?

I have access to a lot of goodyear conveyor belt. I am planning of making a air dam extender out of it. It is pretty heavy but I think it could work good and be basically indestructible.

What are your thoughts?

adjust the driver.

Driver mod is the absolute most effective thing you can do. It's not just a single thing that can be explained in response to a new user's introduction post, either; each person has to read about all the different things we do and decide what will work best for him.

There are some vehicle modifications that can be done. Most of them are small and have little effect. A few are small and have a decent effect, and most of the large ones can't pay for themselves even when gas is $4/gallon.

The first vehicle modification I always recommend is to find the highest comfortable tire pressure you can use (without exceeding the tire's maximum, stamped on its sidewall). This can have quite a large effect for some people.

What engine is in your Grand Prix? The 3800 is known for being a great engine all around -- great efficiency, great power, great longevity.

Yeah unfortunately i have the 3.1 I have been planning on putting the tires around 40 for a while but I am not at my house and dont have a compressor.

I have seen good reports about the 3.1's fuel economy. I had the 3.1 in my '97 Grand Am and it died prematurely, but I think that was due to my abuse. I have no idea what kind of fuel economy it got, that was the furthest thing from my mind at that time...

This tank I am trying to be a more efficient driver. I am just starting with not jumping off from stop lights and trying to time getting to the light when it is green and coasting as much as possible. I also am using the cruise control more.

My motor has been through hell. I am very surprised that I am getting as close to epa as I am. I am the 3rd owner of this car but I know both of the previous owners and, just to show maintenance, Im about 90 percent sure that when I got the car with 135,xxx miles that it had the original brake rotors. And that it has never had a tranny service until I did it. While I have owned it the water pump went out and overheated, blew an intake gasket and ran with a coolant oil mix for lubrication for a good 10 min while I limped it back to my house, I had to it was in the middle of no where with no way to tow for at least a few days.

All fixed up now and I might have 700 in the car including parts and such.

Here's a good thread on aero mods. Also check out the threads in CO ZX2's signature. He's seen some fantastic results. www.gassavers.org/showthread.php?t=2173

I'm gonna guess that if the belt material flexes under the force of the wind at speed then it may not be that effective. I spose if ya brace it really well it won't flex much though. How much of it extending down are you planning?

Its half inch thick reinforced rubber. It might flex a little bit but I think that if it had any curve at all it would stay rigid.

Thanks everyone Ill look into some other stuff on this site there seems to be a lot of info.

My goal for this tank is 300 miles.

300 miles? In town type driving? that should be easy, in the winter I can get 350 miles on my GP, '02 with the 3.1L. Granted you have quite a few things stacked against you, but I have faith. Tis a shame that GP was so abused, they are quite nice cars when taken car of.