I went pretty deep into the oil rabbit hole. There is a HUGE amount of mythology and while there's a lot of science, it's proprietary so it's pretty tough to separate the wheat from the chaff.
One member of our Cobra Club is a retired R&D oil that specialized in performance oil development, including coordinating with sponsored race cars to get them the oil they wanted/needed. Back then the preference was Delo 15W40 diesel oil which had a 1200 ppm ZDDP concentration. Chevron has reformulated Delo and replaced most ZDDP with other anti-wear additives, so his recommendation was Delo plus a ZDDP additive.
I did some more research and discovered that Shell Rotella 15W40 still has 1200 ppm ZDDP, so that's what I will be using on my flat hydraulic tappet big block. Here is the email exchange I had with the Shell tech expert. I don't understand why Chevron felt compelled to lower their ZDDP while Rotella is still at 1200 ppm?
Dear sirs,
I need a recommendation for engine oil.
I'm having a Ford FE motor built and the engine builder recommends hydraulic flat tappets for reliability given the relatively mild cam he's using:
Intake Duration: 274 (230 @ 0.050")
Exhaust Duration: 286 (236 @ 0.050")
Intake valve lift: 0.560"
Exhaust valve lift: 0.560"
Lobe separation: 110 degrees
What oil do you recommend? I'd prefer not to have to use a ZDDP booster, although that is an option and may be more cost effective than some of the specialized race oils available. I understand the 15W40 Rotella T4 diesel oil used to have higher zinc, but does it still have adequate ZDDP to provide good lubrication for the motor?
From: shelltechnical-us@shell.com
To:
Sent: Tuesday, October 31, 2017 6:51:33 AM
Subject: RE: Oil Recommendation for Ford FE Engine with Hydraulic Flat Tappets
Hi Evan,
For the flat tappets, I’d use the Rotella as it does have more zinc/phosphorus than gasoline engine oils. The Zinc is 1200 ppm for most grades including Rotella T4 15W-40.
As for the numbers you’ve provided, I can’t correlate that to a zinc requirement. Your cam manufacturer will have break in instructions and will probably require extra anti-wear additives during break in.
Regards,
Keith Perry
Shell Technical Information
(800) 237-8645 Option 3, 1
Email: shelltechnical-us@shell.com
Technical data sheets and SDS for current products may be found at: www.epc.shell.com
By the way, the retired oil engineer did not have any kind words for 540 Rat's pseudo science (I was pretty impressed with his smoke and mirrors, but they were quickly debunked by an expert).
The information on BobistheOilGuy seems pretty solid.
https://www.bobistheoilguy.com/ I'd also recommend emailing the oil tech lines--I got good information from Chevron and Shell.
If you don't like the idea of running diesel oil, the Brad Penn, Joe Gibbs, Valvoline VR1, etc. also have zinc in the right range (seems 1000 to 1500 is the sweet spot--less and there's not enough protection if the parts "kiss", more and you run the risk of surface degradation from ZDDP causing surface microcracking). A gallon of Rotella is just a little more than a quart of the specialty oils, however, so I'm going to give it a shot.
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