Im going to get 18's instead of 17's...and i was just wondering if i would have any problem with clearance...also will i be slowed down by the bigger wheels and will it affect my gas mileage???

245/40ZR18
yeah, even if they are a little lighter than your stock wheels, because of the bigger wheel size, it will take more energy to turn them so your car will be slower...depending on the weight of the wheels will depend on how much slower your car will get...not sure about gas though

Thanks for the info and do you think 18 x 8's is to wide or should i stick with 7 or 7.5

Keep in mind with any upgrade wheel you have to be carefull because you have less tire. Anyway, you can fit a 9" wide wheel on fine with a 255 wide tire. Also you can fit 20"s...use coilovers if you get them and those can only fit 245-35's. And back to your question I say if you want 18"s get 18x8 with 245-40's should look good and if you want more tire get 245-45's that will fit...But with any upsized wheels your speedo will be affected and gas will be as well.

I think that you should go on...

18x7.5 with 235/45 cuz then they don't need more power to turn the wheel as much as the 245's and they are lighter(and cost less)

i say 18x8

Thanks guys ill keep in mind all of your opinions when i decide....

18x8.5 min watch your ofset make sure it is flush with the arches (if that is your taste, it is mine). Run a 235 on the 8.5