Hib,
I've read both of your articles. . .both were very good. . .and I now use them as the current bible on this subject. I just wished that you had been able to include Royal Purple 5w-30 or 10w-30. . .I love that oil . . .
-Bolisk
Royal Purple was not included to two reasons:
1) It's no better than some of the other synthetic products discussed.
2) I researched RP extensively three years ago and at the time, its own marketing information indicated that in tests it conducted, it was no better than the leading (at the time) brand of ester-based synthetic engine oil.
3) Also, some of the research I had indicated that certain of Royal Purple's engine oils and gear lubricants were not as good as other products, however, my guess is that, at this point in time, Royal Purple, the responsible company that it is, has matched the quality of other, premium, synthetic engine oils.
Getting back to your responce to my earlier post, I understand that ZDDP levels vary greatly with engine modifications (stock to agressive).
ZDP levels DO NOT vary with engine modifications.
What varies with valvetrain modifications is the
need for ZDP
I know you have mentioned stock configurations being OK for 800ppm. In that statment were you including a 1970 LT-1 as being well within the 800ppm need? Or is an LT-1 considered more agressive then normal. . .even though it is "stock"?
Read the stories "between the lines" and you'll see there are some flat tappet cams in factory "special high-performance" engines from the late-60s and early-70s which are "marginal" or "right on the line" with pressures at the lobe/lifter interface right around 180,000 psi. GM examples of this are the mech. lifter cams of in 327/375, early LT1, ZL1, L88, etc.
If you have an engine like that, you might be ok with an ILSAC GF4 or API SM oil, but if the engine's not stock, is not in perfect condition or it gets driven hard, I'd use something different, such as the products discussed in the "solutions" section of the second part of that series.
Admittedly, during the reasearch for the series this issue was one of the only disagreement I had with GM's Bob Olree. He felt *any* OE flat tappet was ok with GF4. I disagreed and, in the articles, suggested that readers with stock, spec. high-perf engines need to consider going to about 1000 PPM phos.
