No cat mileage

[ParkCityXJ]

Has anyone noticed a change in mileage (good or bad) when removing the catalitic converter, or changing to a high flow cat??

[Ron4x4]

I redid my whole exhaust with a header, high flow cat and a terminator muffler with 2.5 an 3 inch pipe and I do get about 60 more miles per tank.

[xj92]

I put in a new high flow cat, glass pack, & tail-pipe and noticed about 1 mpg increase in gas mileage (I calculate my mileage with each fillup by dividing the miles driven by the gallons to fill it up).

[Mikel]

Keep in mind that these numbers are probably with people ditching their old exhaust and old cats. It's like people who get a new carb and say it's so much better than their 22 year old original, un-rebuilt carb! :lecture: :laugh3:

[xj92]

There's no probably about it, we stated exactly what changes we'd made.

[Harvo]

My cat is gone and it seemed to hurt my milage. My wife was driving it at the time though, so I couldn't tell you definitively how much.

[Cherokee91Red]

I'm waiting on a gasket for my exhaust, right now I've been running downpipe only, and it has definitely hurt my gas mileage, I lost about 3 mpg.

[natep1]

I put a 2.5in cat & resonator on and have gained about 2 mpg. On a side note, I lost MPG when I staight piped my YJ.

[xj92]

I also ran just a header and down pipe for a couple weeks before putting the rest on, and it hurt my mileage and power quite a bit.