Ive got an 01 s80 t6 with executive package that i bought back in may. I paid $400 for it and all it need was new struts, had a small oil leak and, I had to bleed the brake lines. (I have no reason to lie. I honestly only paid $400!) It runs like its brand new. Absolutely no rust, or problem at all. Brand new tires and all. But there is one thing i cant figure out. im only getting an averge of about 10 mpg city. 15-16 mpg highway. With the price of gas these days, i cant afford that. (who can?) So my question is, could this terrible mpg be caused by: my tire size (I have 235 50-17 when i should have 225 50-17) or could it be just the age (137,000 miles) or could it be just the engine size (2.8L twin turbo). I have the original window stick from the lot it was purchased off of from the previous own back in 2001. It says it should get 18 city and 23 highway. So if anyone has answers to my problem or opinions, it would be greatly appreciated. Thanks.

 

The wider tire will lead to poorer gas mileage because of the increased rolling resistance, but I don't think it would be THAT bad. My first thoughts are a faulty or failing MAF sensor, a stuck thermostat, or a brake that's stuck on.

Edit: Also, did you have the alignment done after changing the struts?

 

I come from a long line of family mechanics. Had the tires rotated and I realigned and balanced. All the electronics are good. The E-brake is not working either, so i know that its not that. It might be a brake because im thinking that it had rear end damage with the previous owner because when I pulled the driver side rear wheel off the rotor was a little mangled. but it works perfect. I have no check engine lights ect. The service light comes on when it first starts up but after it warms up it goes out. thats why im just so confused as to why im getting such bad gas mileage. I think im going to get new tires over the winter and ill get the right size. so hopefully that might fix it. i just cant think of anything else.