The main reason just being I like more rubber on the road. My efficiency is very good, I don’t actively keep score but on my winter tires my 30 mile averages on the screen shows between about 290-380. I don’t get off the island much so most of my driving is under 60 mph but I do haul 450-700 lbs for a day every 2 weeks. I almost always precondition.
Thinking 265/45 square was as big as I could go, I bought 20x8.5 rims. I don’t know if 275’s on those would work or not. I don’t remember the offset but 35 sounds familiar.