If synths were cost effective then all the major fleet operators such as FedEx, UPS and the USPS would be ordering their vehicles and maintaning them with synths but they don't.[/quote]
do your research buddy. all eaton, axles, roadrager transmissions, and what else you want me to list? ya, the rear ends require syn, the trannys have a 60k miles change interval, as per eaton road ranger, with reg oils. and guess what? its 500 with synthetic. its on their site, and in the rebuild manuals. u want a link?
heres the link for the axle lubes
http://www.roadranger.com/Roadranger...ight/index.htm
heres the change interval as suggested by the manufacturer.
http://www.roadranger.com/Roadranger...hart/index.htm
fleets? i know a little about fleets since i was the sole mechanic on a fleet of 23 class 7 and 8 trucks and trailers.
synthet IS better, which is also why gm uses it in their hp engines such as the corvettes. and as far as recommended intervals per gm? at 10k miles my car said it had 32% oil life remaining. sorry. not going that long, even tho i do use mobil one and it would probably be ok.
if yer gonna make a referance to fleets, try working on them so you have a solid base to your opinion. or just read what the manufacturer ACTUALLY says before quoting them. and just in case you dont know what eaton roadranger is, they make almost ever single non-light duty axle and transmission, the other major one is rockwell-meritor, you can check them out as well, im sure its about the same.