Theoretically bigger tires might actually help your gas mileage as they will put you in the equivalent of a higher gear when cruising on the freeway. But they will make your mileage LOOK like it's worse because they will throw off your odometer so it looks like you've driven fewer miles (on each gallon of gas) than you actually have. This odo error also extends your warrantee period and makes you feel like you live closer to work. Big tires also make you more vulnerable to speeding tickets because your speedometer is off, and your top speed is increased as the limiter kicks in later. :-] And they make your VX look like it was always meant to look! I've seen a VX with the Nittos and I want them soooooooo bad but I couldn't find any when I had the money a few months ago so I'm going to finish wearing out my Yokos this year and get them next winter. Post back if you find them and where and with pictures of your truck before and after!