I started around 42 from delivery. It was fine and had about the rated efficiency. I adjusted to 45psi after a couple months and definitely had better efficiency on average. I also didn't think it really affected the ride comfort much. I just bumped up to 47psi and I can definitely feel it in the ride. So far very limited driving I have not noticed any additional efficiency. I will keep it this way for a week or two just to monitor for any effect on efficiency, but will probably drop a pound or two for ride quality. I am on 18" Michelins.