I've been using 15W-40 Royal Purple in everything for years and I've never had an oil-related failure.

If I could drink it, I would.

After reading several articles on the subject the most knowledgeable people in the petroleum business maintain that synthetic base stocks are not any more slippery than conventional oil base stocks. What makes oil "slippery" or "slipperier" are the friction reduction additives that are added to the oils.

Bob:

"Synthetic base oils have lower coefficients of friction than do mineral oils. Synthetic oils also have higher bulk film strengths (as proven by ASTM 3328), better thermal and oxidative stability, and better base VI's than do mineral oils.

Synthetic base oils have better friction modification (reduction) as compared to mineral oils. FM additives added to BOTH synthetic and mineral oils reduce the friction coefficient of the oil by another magnitude.

No currently available (to consumers) oils by themselves can provide Extreme Pressure reisistance without additives. This is where the AW/EP additives come into play. Some of these additives are ZDDP, MoTDC, SnTDC, Boron (Borate-type) Esters, concentrated Calcium Carbonate Sulfonates, Phosphate Esters, Sulferized olefins, Nitrogen compounds, and others".



If the oil is API certified and it is "SL" whether synthetic or conventional it will perform in a similar manner.

Every BMW; Porsche; Mercedes Benz; C-6 Corvette; Viper all require Mobil-1 synthetic oil. They all have roller rockers. No flat-spotting after lots of tests.

Why would synthetics flat a Merc 525 and not all these other vehicles that are also run very hard at times with rollers?

I think synthetic oil and flat-topping is possibly more a myth and not a fact. Take out the friction reducers and you increase wear. I say re-evaluate the roller/rockers you are using first and their tolerances.