Gas Mileage

[RedLexusSC400]

I bought my SC400 just under 100k a little more than a year ago and I averaged about 19.5mpg in the city, and 24 on the highway. Now, at 130k, I got 16.6 in the city... Running the same premium gas, and even lightened up on my driving style. The car still runs great and all I have done was remove the third cat, put an x-pipe and a couple flo masters. Also recently put a Do-Luck kit and some wheels on it but the mileage was already bad before that. I treat her good, oil changes and everything on time. The only problem I have with it is a SLIGHT rear differential leak.

So anyone have any idea why I could be averaging almost 3 miles less per gallon?!

And also any recomendations on what I can do to help?!

Thanks

Bry

[JDOwen2]

Have you done the BFI yet? Maybe your new tires/wheels are heavier or different diameter. Tune-up lately?

[SCdriver]

I agree that different sized tires and rims can change you odometer readings if they change the rolling circumference of your wheel. Keep your tires properly inflated and you might try adding 20oz of techron complete fuel system cleaner into half a tank and then fill it up to 3/4 to full and run it through. If you have not changed your air filter in the last 20,000mi or so you might consider doing it now. Otherwise,your you might ask Lexus if your differential leak is causing slippage and poorer gas mileage.