sudden bad gas mileage help!!!

ok so i 80000 miles on my trd 4 door. i changed spark plugs (denso), throttle body spacer and cleaned throttle body and MAF sensor, sea foam in gas tank, royal purple in t-case and diffs, royal purple oil change, water wetter in radiator, and complete ome suspension with 285/70/r17 mickey thompson mtz. Now im getting 240 miles on a tank of 93 octane. anyone else ever had this problem. i doubled checked everything and its all perfect so im stumped.

 

It's your 285 tires. The increase in radius and weight eats MPG's. Most guys with 285 tires are around 15-16 mpgs so it sounds like you're in that range.

 

i guess i can live with that. i almost had a heart attack thinking something mechanical was wrong. thanks brother.

 

You don't really think tire size will drop your mpgs but it does.

When I had a 245 tire: 21 mpgs

Upgraded to a 265 tire: 18 mpgs

A 285 tire will drop me down to a 16 mpgs. Even though they do look awesome and perform off road, I don't wheel enough to justify mpgs that low. haha.

Np. You can drop 3 grand and get re-geared so you can gain some performance and MPG's back sometime down the road.

 

Also keep in mind that with the new tires your odometer is off and you are traveling more that 240 miles on the tank. Check your old tire size vs. new size on a tire calculator and see what the difference is.