gas mileage has dropped

[2004rnr]

i have a 2004 4runner sport edition V8 2wd. i don't quite remember exactly how many miles i could go on a full tank, but i think it was like around 350 miles. i recently lifted it and went to a 265/70/17 bfg a/t from the stock 265/65/17 flops. i now can only go about 300 miles on a full tank. is this possible? on top of that i just installed the magnaflow cat back exhaust and i thought it would give me more miles on the tank (like someone on this forum claims), but it didn't give any improvements on my gas mileage. i do feel a little more power, which is always a plus.
does anyone have any input.

 

[Bobby]

The larger tires will register less miles on your odo. It will also depend on what tires you put on. Most AT tires have more drag than stock tires which are all season highway tires. The exhaust will give you a bit more mpg but not much.

 

[HuntRunner]

In my experiences, every time I have gone up in tire size (especially if it was changing to a more aggressive tread) I have lost in mpg and noticed a decrease in power.
Part of this is due to rolling resistance, weight of tire, and tire foot print and part is due to the change that is made to your effective drive ratio.

 

[greasefingers]

Replacing a CAT-back only, will not improve mileage or hp. It takes a lot more money and hardware to accomplish this and actually notice/measure an improvement.

 

[mikes4runner]

Replacing a CAT-back only, will not improve mileage or hp. It takes a lot more money and hardware to accomplish this and actually notice/measure an improvement.

Right on, funny how people think the put on a cat back or a CAI and they are going to feel HP.

Anyway like others said it's your tires.
Make sure you have the proper PSI in them.


Mike

 

[02SE]

Turning bigger, heavier tires will hurt mpg. Even if the BFG's were the same size as oem, they would weigh more, because they are an LT tire, with more rubber, steel, etc. And they have a more aggressive tread than the oem tires, which increases rolling resistance. (As was previously stated)

Add a lift, and it will hurt mpg even more, due to more aerodynamic drag.

 

[Bobby]

Right on, funny how people think the put on a cat back or a CAI and they are going to feel HP.

Mike

That actually depends on the vehicle in question. I put a cat back and air filter in a 96 Maxima and it definitely had more pull. Did the same with my M3 and there wasn't a big difference. Point is, the maxima exhaust is very restrictive and built more for quiet than the M3 exhaust which is very efficient with a low rpm valve in the chamber to give a little more back pressure at low revs for more torque.