1986 Donzi, Gen 5 502 recently rebuilt, 12 hours on it, roller cam...oil change prior to winter, builder specified never to run synthetic...

I thought of Lucas Hot rod oil 20W50, what say the masses?

My first question would be why would a builder specify not to run synthetic??? Did he specify what weight to run??

If no synthetic, then I'd run Valvoline VR1.

Crower recommended not to run synthetic with their hi po solid rollers. I have been running Driven semi synthetic.

Pick your poison - few good choices out there. VR1 is always good and has been reasonable $$$ on Amazon for a little while now

I just run M1 15-50 readily available at Walmart…….

On my Saris Racing 540 build, Jason Saris recommend Pen Grade 20 W 50 synthetic blend.

Padraig

I run Pen Grade 20w50 also.

AMSOIL 10-40 full synthetic high zinc. 300 trouble free hours on NA 588s. That’s what original engine builder recommended. They’re being rebuilt now by different engine builder, we’ll see what he recommends.

VR1 is a solid choice. And $26 for 5qt bottle on Amazon typically.

https://pqia.org/lucas-hot-rod-class...-40-motor-oil/

This is Lucas hot Rod 10w40. I assume their 20w50 is similar.

Either way...their zind is way too high. Needs to be 1200-1600 ppm. Any higher and it's too much...it causes wear and problems. The film it creates is too thick and brittle.

Calcium is also way too high. SP rated oils drop the calcium to around 1000ppm from 3000ppm. Calcium...as a detergent would fight the zinc and clean it away.

I would never use a Lucas product if it was free.

VR1 seems to be the best and easiest access conventional perf oil. Has great zinc and calcium ppms.

Lake Speed Jr had am episode speaking to conventional vs synthetic on high pressure contact. The conventional had a linear film strength...all.the way to concrete level of solid support. The synthetic would fall flat at higher pressures allowing metal to metal contact.

I can't find the episode...but I'll keep looking.

The slippery factor of synthetic eventually has to pay the piper.

Lake's solution was to use a semi-synthetic. Best of both worlds for extreme pressure contacts. Pretty much a BBC perf marine engine...is extreme pressure contacts.