OK, I need the help of the experts here, and correct me if I make a mistake.(I often do) From reading the various posts on this forum, I understand that when the motor-oil rating was changed from SH to SJ( in 1996, I think), a significant amount of friction-reducing additives were taken out to keep from contaminating catalytic converters. I think I understood it to be the 'Moly' that was removed, but I'm not absolutely sure. Furthermore, I think I understand it that Valvoline in particular with thier 'Max-Life' oil, and other major brands with thier high-mileage oil formulations basically just put the friction-reducers back in their oil and marketed it for 'high-mileage'(75,000+ miles) cars that would coincidentally put it right in the middle of the mileage range of cars that were originally spec'd to use SH. If this is basically all true, then I have a couple of questions: First, if this 'high-mileage' oil is basically chemically the same as SH rated oil, then would it satisfy warranty requirements of newer engines spec'd to use SJ & SL?. We have a lot of customers that use this oil in newer engines. Also, putting the warranty issue aside for a moment, would this 'high-milege' oil in fact actually be better for a newer engine, disregarding the converter issue? Secondly, can a readily-availible additive be put in SL to bring the level of friction-reducers to the previous higher levels? Without upsetting the normal additive chemistry of the motor oil? I also have some personal concerns: I use Mobil 1 exclusively, and have always had good experience with it. My cars range from a 400 horse 429 Cobra Jet 1971 Mach 1, a 300 horse Z-28 with a ZZ4+ crate motor, 3 late 70's Ford products with 460's and a 95 Olds with a 3.8 litre V-6. Will I be able to increase the level of protection in these engines by adding anything to the Mobil 1 oil? I always change the oil at 3,000 miles, but sometimes it takes a year to get there. I know this is a long complicated post, and I appreciate everybodys help. Kit.