My pleasure and good luck with your decision. I know it is not easy.Brad
Thanks for the detailed reply. I will think hard about your opinion and recommendations.
It really depends how you're going to drive the car (street, cruise, or tracked hard) and the external temps. If the oil gets too hot it'll thin down to water & can't provide sufficient film strength for proper protection. The HTHS rating is a good way to compare this aspect.It sounds like the the best of both worlds is a synthetic with good additives and a higher weight (number on the back end) for high temperature stress viscosity or a 40 weight.
Any other input would be appreciated....
Red Line uses a Group V, polyol ester, basestock, as compared to a Group IV, PAO basestock used in all AMSOIL fluids except their XL line which uses a Group III, highly hydroprocessed mineral oil basestock. Castrol and most other mainline synthetics use a Group III. Royal Purple doesn't specify what they use. Historically, Mobil 1 has used a Group IV PAO basestock, but recent analysis by guys on the oil forums indicate that they are now using a large percentage of Group III basestock in their oils. Mobil 1 has been very tight lipped about any change and their website doesn't provide much info.wow, lots of good info. Anyone know anything about Redline?
Keep in mind that the new CJ-4 diesel spec put similar, but less stringent limits on phosphorus as did the SM spec for automotive oils. The CJ-4 spec is 0.12% or 1200 ppm. There are still some diesel oils on the market, such as the AMSOIL Heavy Duty Diesel 5w30 that 4wheels uses, that are CI-4 plus and can have higher ZDDP levels. But again, this is somewhat brand dependent. Just because it is CI-4 plus vice CJ-4 doesn't mean it will have higher ZDDP, just that it can (and the AMSOIL HDD 5w30 does). AMSOIL makes a CJ-4 diesel 5w40 and intends to keep the CI-4 plus 5w30 (and 15w40) in production as long as there are pre-2007 diesels on the road... which obviously will be a while.i know a little bit about the zinc deal,and that alot of people are using diesel oil because of that.