you my get a slight boost in city (1-2 mpg) as the truck wont have to work as hard to get moving. on highway probably the same. maybe a little lower. gonna work the opposite as it did for in town as now you are running higher rpms on the highway than before but with the rpms you listed you might drop 1-2 with the 4.56 on highway and a little less with the 4.10's. hard to say exactly so those are guestemates. when i went with my lift and 35's I did 3.73 to 4.10 and maintained my average economy (12 mpg) from stock, but I did it as my commute was mostly highway. in your case since you say you dont do alot of highway those RPMs still look really good (I sit at 2000 @65 with mine and all freeway is about 13 mpg). I would think overall you will see a small increase (hell in these getting an extra 1-2 mpg is around a 10% increase) in fuel economy either way. Being that you are going from a stock 3.42, and from reading your driving style, my .02 is that a 4.10 will give you a good mix of highway fuel economy and low end power regardless if you choose to stay with the 35's and moreso if you go down to the 33's. If your stock was 3.73 then I would have said 4.56 for the same reasons as in that case 4.10 would be too tall.