This might not be in the spirit of this forum, but I commute in my civic. I'm looking for any mods that can increase both performance and gas mileage. Does a CAI or catback replacement increase gas mileage? Are there any mods that help both?

 

intake,

and a rule of thumb, more performance=less mileage

 

anything that allows the engine to naturaly breath better will do both. Obviously though the higher the rpm and the faster you go the less gas mileage you would get.

 

yup... there's a reason Dodge Vipers get about 13mpg.

An intake and exhaust won't really affect your fuel economy one way or the other, though. Just watch your driving habits; alot of people tend to drive a little more aggressively when they modify their cars, leading to lower fuel economy.

 

I/H/E with a flow-through cat can help both mileage and performance. So can a better clutch, better tires, and lighter rims. Shaving a little weight can improve the power-to-weight ratio, as well as improve mileage, but I recommend shaving weight from the back end of the car only (I wouldn't personallyuse a lightweight hood on my Civic, but deleting the backseat is a possibility), so that front-end traction isn't compromised. You would also do well to use a fuel-system cleaner regularly, to keep your injectors misting well for efficient combustion.

 

Don't use your A/C unless you absolutely positively must have to.

Also, inflate your tires to the max. It may be a bumpier ride, but it does help with fuel economy.

 

My dodge p/u gets about 14 mpg, it's a dodge thing....

 

No! Don't Over-inflate your tires. Just inflate them to specs and check them often if you drive alot.

 

I did *NOT* say to overinflate. I meant if the tires max 45 PSI cold, put 45 in the front, and a few PSI less in the rear. This also helps when it is wet.

 

But when its hot, heat expands. So if it says 45 PSI, shouldn't you put 42/43?