How important is the catalytic converter for gas mileage?

[WestCoastDan]

I stopped calculating it after several repeat performances in the ‘less than I want’ category.
Even with stock tires we were always lucky to come anywhere close to 20 MPG.

 

[Peppergat]

I stopped calculating it after several repeat performances in the ‘less than I want’ category.
Even with stock tires we were always lucky to come anywhere close to 20 MPG.

I’ll get there pretty quick I’m sure.

 

[R49]

19, but it shows empty when there's still about 5 gallons in it.

Mine too. Fuel light comes on and I still have 5+ gallons.
Getting 15 mpg so no complaints

 

[Mike_H]

12-15 MPG is pretty normal. Sounds like your in the ballpark.

 

[MRChiefE7]

2005 LJ, 4.0, automatic, 33-12 x15 tires, 3.73 and the best that I get is11.5 to 12 MPG around town.

 

[Peppergat]

I replaced the plugs and, all 4 02 sensors. I’m going to fill up in the morning and see what I get. I may actually be in the ballpark. I’m just so used to my other vehicle with its good mileage.

 

[KennethS]

My fuel gauge is not very accurate. 19 gallon tank and it will show 3/4 after driving 50 miles, then as said above, when the needle hits E there's still 5 gallons left. I use the trip odometer more than the fuel gauge to know when it's time to fill up. Usually that's around 250 miles.

 

[PRNDL]

Light came on and I filled up. 200.5 mi / 15.4 gal = 13.0 mpg. Better than expected.

 

[Peppergat]

Light came on and I filled up. 200.5 mi / 15.4 gal = 13.0 mpg. Better than expected.

Since I replaced the spark plugs mine is doing better. I’m just a tad over 1/2 of tank and have 105 miles on it. I’m anxious to see just how much difference it will be.

 

[Bammo68]

I’m going to fill up in the morning and see what I get. I may actually be in the ballpark. I’m just so used to my other vehicle with its good mileage.

The thing that really threw me when I first got my TJ was that there is "filling her up" and then there is "fully filled". My mileage (kilomeratage?) was sometimes just awful and it comes down to the fuel filler constantly tripping the nozzle. Turned out I wasn't fully filling the tank each time so it was sometimes giving me results of 11MPG and sometimes 16MPG. If I fully fill it I get between 14-16MPG depending on city/country driving. The dead giveaway that I haven't properly filled the tank is if I see the gauge drop below the F mark within 30 or 40km of the fuel station.

 

[freedom_in_4low]

With the inconsistent fillups the only way to know is keeping track over the long term. I may get a tank close to 15 followed by a 10.5 and it could play my anxiety against me but Ive tracked every fill for 13,500 miles with an app called Fuelly so I know that my mileage really is 12.5 average with 35s and 4.88s.