How much of a decrease in MPG (if any) can I expect if I replace the OEM wheels/tires on my '07 Toyota Prius?

Question

I'd like to replace the stock 16" wheels and 195/55-16 tires on my 2007 Toyota Prius with 18" x 7.55 wheels and 215/40R-18 tires. Should I expect a significant decrease in MPG? If so, I don't want to go through with it as that defeats the primary purpose I bough the car. I should have paid more attention in Physics class! :-)

Answer 1

I disagree. The wider stance of the tires means more friction on the road plus more drag regarding wind resistance thus lowering your fuel economy. The most common reason why people buy these tires is the benefit of greater control during agressive handling.
However the loss of fuel economy should be minimal. Perhaps 2-3 mpg. If you can afford puttin on the 18", it should be no prob for and additional $1.50 extra to fill up the tank.
I say get em, ya only live once.

Answer 2

Check the tirerack.com site before you make this decision.
If you look under any specific tire (spec). you will find that by changing your standard tire size to a 215/40/18 the tires will roll a lot less RPM's. In tire language that's "revolutions per mile" In your case your standard tire rolls 854 times per every mile traveled. If you change to the larger 215/40/18's the tire rolls 811(rpm,s). What this all boils down to is your speedometer will read nearly 5 mph slow. If you can live with that go ahead.
Another person has brought your attention to the fact that you probably will loose gas mileage along with acceleration and overall power. The motor will be turning less RPM's and that means you'll have your foot in it a lot more to do the same job. The little 4 cylinder motor needs to buzz up not down. Either way you'll not be happy. You will have more rolling resistance because of the slightly fatter tire. If you choose to do it be prepared to inflate the tires with nitrogen to within 4 lbs. of the max. tire inflation pressure to help decrease rolling resistance.
Personally I wouldn't do it. It'll make your car "dogie" because of the decreased motor RPM's.

Answer 3

if you measure the height of your 16". A 16" tire may have 25 inch's when the 18 in tire may have 24. so don't go by what people tell you about drag and or wind when its the final tire height that is important. A 225/40ZR18 will be the same size as your 16 which is 25"

Answer 4

as a manner to recreate genuine existence making use of circumstances the EPA recalculated the way it determines MPG. All automobiles MPG will circulate down for 2008. however the numbers would be plenty nearer to what you get while u purchase the motor vehicle. (MPG)

Answer 5

No, if anything you will improve gas mileage. Slightly. If you have more grip from a dead stop, your tires spin less, thus saving you gas. The more traction you have, the better your mileage.