i've heard that adding more horsepower you'll see lost in mpg. is this true? all i have is an hks exhaust and an injen intake i know there not major mods but do you get a lost in mpg from adding these? i've heard from adding more air in will cause lost of mpg too the more horsepower you have ( if you drive normal) you get better mpg over stock. which is true? thanks

 

Extra power comes from the ability to burn more fuel which means you use more fuel.

Your intake and exhaust are such minmal power adders on a stock motor that you will see very little to no difference.

Another thing to consider is efficiency in this whole equation. You can make more power and use less fuel but that is getting a little off the main point.

In summary don't overthink this one too much and enjoy your parts and same gas mileage.

 

possibly a turbo..which is recycling partial exhaust which you were giving away. CAI has a similar principal..less restriction, more air...pressurized. Effects on mpg may not be huge.

and unless i am mistaken, power comes from combustion which can occur a number of different ways. You can increase combustion without fuel.

 

Some factory turbo cars (Subaru and SAAB 9-2x Aero for instance) have seen better mpg after a few important mods. I think the SAAB guys that have kind of a basic layout for the stage II is where more mpg really pops up.