if i had my way, i would run syn in everything i own. but with so much equipment and all the trucks, no way i could afford it. with the oil article posted not to long ago, i would say with book recommended changes, just about any quality oil would do. i went from useing 4 different brands to 3. delo,shell rotella,shell rotella syn, and tractor supply's traveller brand. incidently the traveller brand is still ci rated, which is said to be better for engines with solid lifters. i have used it for atleast 12 years in my equipment , and will continue to use it. delo and both shell's, i use in my dump trucks and pickups. although i have phased out the rotella dino oils, and replaced them with the traveller brand. clear as mud? anyway, i have spent quite a few hrs in a engine rebuild shop, and i have seen first hand what high mileage engines look like run on both delo and shell oils, as well as mobil delvac. a year ago i wouldnt be ashamed to run any of those brands. with these newer cj rateings, i have my doubts , and simply would keep closely within the change intervals set by the owners guide. with my winter oil changes fast approaching, i will likely drop the shell synthetics[now cj rated], and replace them with amsoil syn's.