[buschman]

Hello all, new forum member here. I drive a 2018 Subaru WRX. I know, not a traditionally hypermile type car, but I like it cause it does everything and is an engaging car to drive. That being said I do a lot of highway driving, at least 90% of my miles are highway miles. I have a set of summer tires and winter tires. I swap them on my stock 18"x 8.5" rims.

I want to get a new set of rims so that I can swap them in my garage. Most of the aftermarket rims for the WRX come in the 8.5" width and the 9.5" width. I'm debating on which one to get.

My current tires are 245/40R18. If I got the 8.5" rim that is what I would stay with. I'm getting decent gas milage with these. 31.2 mpg over 36K miles. I can usually get 32-34mpg per tank.

If I go with the 9.5" rim I would probably step up to a 265/35R18 tire. I've been reading about the pros and cons of doing this. I'm interested in hearing thoughts of those that focus on gas mileage. Obviously there are some performance and appearance gains by going with a slightly wider tire. Also keep in mind the rims I will be getting will be lighter than my stock rims. So I don't think the weight gain of the wider tire will be relevant. Overall I will be losing rotational mass even with the wider wheels and tires. However, with the wider tire I would think I will be increasing my frictional loses or rotational resistance.

I also read that wider tires can be a benefit on the highway, where I spend most of my time. I'm not sure I understand the concept on this theory.

I know it's not a huge difference going from a 245 to a 265. But once I plunk down this money, there's no turning back. Wanted to hear some perspective before going this route. Your thoughts about this subject are appreciated.