Yes, it will seriously affect your gas mileage. And checking the tire pressure does not cost anything...

 

i know, ill give the tires a check before i leave tomorrow, any idea what a 205/40/17 tire should be at?

 

Frankly no idea. I always drive on stock or plus zero sizes...

 

I just checked mine because I thought I was getting worse. I get 276 miles on 8.919 gallons of 87 octane for $22 bucks. that equals out to about 30 miles per gallon...not too bad.

For the tire pressure, 30-35 pounds is good. It should say on the tire.You don't want too much pressure or you'll feel every little bump in the road. Good luck with your mpg

 

Anything??

95 DX hatch 186K miles. Had bad mpg after I swapped in an exhaust manifold.It had come with it's own O2...I should have guessed it was bad...but 40K miles later and a failed smog I replaced it. Noticed that #1 it wasn't at all like the replacement...#2 the A-hole before me cross threaded it and welded it for good measure. #3 the exhaust shop guy LOL and said no way would he mess with it.
The new weldment cost 7.00. The new bosche O2 cost 92.00, and my labor to cut and weld while getting paid at work...priceless.
My old mpg = 30-32
My new mpg is 39-42...after about 1000 miles.

 

I got 410 miles out of the tank once and still had a gallon left. I usually get 35-38mpg on the highway.

 

i got decent gas mileage... around 31mpg, that includes some hard throttling, so all in all, a lot better than what i was getting... also, the tires, i checked them and they were all around 20-25 pounds, so i aired them up to around 35 before i left