The only thing I can think of is that the new SL/GF-3 5w-30's (at least I believe) pretty much have to be manufactured with a group two basestock to be certified, whereas the "shorter-spread" oils, such as 10w-30, could still get away with at least a good portion of group one base...
To bad any good brand new oil is GII base, with even some "GII+", as they border on the realm of being a "pseudo-synthetic".
Lastly, a mineral 5w-30 will not achieve any lower deposit and eventually sludge buildup in comparison to a 10w-30...if anything, it will have a larger buildup level, due to higher VII level (shearing down/leaving deposits and losing viscosity) and slightly less resistance to breaking down under high temperatures/loads (oil coking, etc, etc...)
[ October 30, 2003, 08:58 PM: Message edited by: Jelly ]