So I just recently replaced my cat converter and muffler hoping it would help my gas mileage but I havent really seen a difference. Last tune up was a little over a year ago and only 6000 miles ago. Oil was also changed when I got the converter and muffler in. All I know is I have an oil leak into the wheel well area. Any reason why my mileage hasn't improved much? 94 xj by the way.

 

doing the math wrong? heavy right foot?

 

Neither. I drive good because I don't want to burn the gas so I try not to press down on it.

 

I an averaging about 12 to 13 mpg's. I do all city driving just going to school and back.

 

Check your tire pressure, tread, air filter, plugs, wires cap, etc, any extra weight in you rig your hauling around not needing on a day to day basis, take off ur roof rack if you have one, use some fuel injector cleaner, and seafoam.

 

These things are just gas pigs. OPEC's design to untold riches......

I'm running an HHO generator piggy pack to gasoline and have not yet seen the results I was hoping for. I average 16-18 MPG as a DD around town.

Ended up extending the fuel tank overflow tube and can carry 5 more gallons (total 25 gals) which helps the number of gas stops per month by extending my range about 85 miles or two days of driving.

 

There is no reason to replace a cat unless you were having emissions trouble those are expensive. Try doing a full tune up and fix any issues you have with it. If you are seeing a drop in fuel economy check your injectors, ignition system, fuel pump/pressure, air filter, iac sensor, O2's, etc.

 

The old cat converter was plugged that's why I replaced it. But I was thinking about just a tune up. Thanks guys.

 

im having the same issue in my 88 recently rebuilt engine new injectors new plugs wires cap rotor tps sensor iac and im still getting 11 on average on 31s with 3.55 gears which

 

City or hiway, lifted, what trans?

 

Check for cracked header or other leaks in front of your upstream O2

Any vacuum leaks?

 

I have the aw4 with a 3" and that's mostly highway

 

stock tires?

 

If the cat was plugged then it probably put a thick layer of soot on the upstream o2 causing a problems. Add that to the list when you do a tune up.

 

Well 200 miles a tank is one thing, but how much fuel can you fit in at each fill up? I get 160-180 a tank, but I can only fit 12-12.5gal. a few miles after the light turns on.