Fuel opinion and additives

[Hib Halverson]

Originally Posted by SteelBlueZR1

Regarding recommendations on engine oils and ZDP contents, if you haven't read Marc Haibec's tech paper, you should check out:
http://www.zr1specialist.com/HAT%20W...5%20Engine.pdf

I've read Marc's article–several times. I read it when he first published it in the newsletter and, then a couple more times when I was researching my article on engine oil.

Marc and I agree on many LT5 issues but the idea that LT5s have a problem with lower levels of EP additives in modern engine oils is not a subject on which he and I see eye-to-eye.

My research showed that because the LT5 uses direct acting flat tappets--meaning the cam lobe moves directly on the lifter face rather than on a "finger follower"--the loads at the lobe/lifter interface are far lower than those present at the same interface in an OHV engine. Because the loads are significantly lower, the need for EP additives is less and OHC engines with direct-acting tappets don't have problems with the lower levels of EP additives in modern oil.

This is why engine failures due to reduced levels of EP additives in engine oils have occured only in OHV engines (Small-Block V8s, Big-Block V8s and other pushrod engines with flat tappet cams) or in OHC engines where the lobe acts on a "finger follower".

There are tens of millions of OHC engines on the road worldwide which use direct acting flat tappets. If that type of valve train had a problem with reduced levels of EP additives in ILSAC GF4 rated oils, we'd know about it by now because there would have been widespread failures of cams and lifters in all those engines.

Further, with LT5, at this point in time there are many high-mileage LT5s on the road. Where is the evidence of widespread cam and lifter failures due to lower levels of EP additives in the oil? Not only are a lot LT5s high-mileage, but GF4 oils have been on the market for seven years. You'd think we have lots of LT5s with burned up cams and lifters but...we don't.

Also, the bucket tappets used in LT5s were, also, used in millions of "Quad 4" engines GM built in the late-'80s and early-'90s and a fair amount of them were still on the road in the '00s. If there was a problem with insufficient EP additives in modern engine oil, we'd have seen widespread cam and lifter failures in Quad-4s.

Bottom line: the vast majority of LT5 engines on the road (or the track) will not have problems using modern, GF-4 rated engine oils and 600-800 ppm phosphorous.

Now...you'll not above that I said "vast majority". There might a small minority of LT5s which could have a problem with lower levels of EP additives in engine oils and that's the very few LT5s which have valve spring pressures significantly higher than stock and/or aggressive camshaft profiles reground on stock cams. Significantly higher spring pressure may require a higher level of EP additives in the oil. More aggressive cam profiles reground on stock cams will result in lobes having more lift and a shorter minimum radius of curvature and that will affect the need for EP additives, as well. It is possible that an LT5 with "big" valve springs and/or reground cams will need an oil with 1000-1100 ppm phosphorous content rather than the 600-800 ppm in a GF4 rated oil. Fortunately, there are a number of oil choices with that level of phosphorous.