yup in 1/4 & 1/8 they will help... on the highway at like 100mph they will hurt you... but who cares bout that lol. actually to be hoenst if you do alot of city driving wit your truck you mpg will go up if you do 4.10s if your at alot of highway speeds youll probably lose 1-2 mpg... im goin 4.10s in my sierra when i get the money