I have been driven NHW20 for 12 years and after 180K miles, I have purchased a 1 year old ZVW50. I used to average around 45mpg in the summer and 55 mpg in the cooler seasons on the 20 series. The new car I purchased is on a set of 225/40/18 ZR tires ( the ex owner choice..). But it can only do less than 41-43 mpg. I was expecting better fuel burn on a newer car but not sure is it because of the tire or other factor. I am just wondering what is your average mpg on the stock set of 215/25/17? I am thinking of changing back to smaller tire. Also what is your choice of better fuel burn tires?