Hello everyone,
I have a problem and hoping someone can help me out. Last week, I went from the stock 16" tires to an 18" tire. The next day I had a 550 mile drive while on the road I used my normal pulse/glide driving method and on average my mpg needle hovered in the 30-40 mpg mark. The only bad ting I noticed was that my steering would vibrate on and off when I hit about 70-80 miles per hour. I called a friend of mine who worked at the tire place i went to and he told me that my tires probably needed to be rebalanced. I went to a different tire place to get them rebalanced, the guy there said that all 4 tires were in need of a rebalance which he did and it was fine, he also told me that whoever did my tires put too much air in them, he said they were at about 50psi and that they should be between 30-35psi.

Now my problem is that my steering wheel doesnt shake anymore at high speeds but my mpg need is all over the place, now when I acceperate it goes all the way to 10 and usually stays there and when I take my foot off the gas it goes all the way down to 60. There is really no in between. I just put gas in the tank so my mpg of course went down and checking it to see how it does. But Im kind of concerened

Should I bring the tire pressure up?
Did the tire guy do something wrong???

Thanks
Shawn