I've been doing some comparisons on Castrol RS 10w-60 and decided to involve John Rowland the Silkolene R & D Chemist in my exercise.

 

I sent him a copy of the tech data sheet for this product and asked him for his thoughts.

 

Here is the answer

 

QUOTE:

 

Simon,

 

First, there is something odd about the Castrol Data Sheet. They claim a ‘CCS’ by which I think they mean a ‘Cold Crank Viscosity’ of 4200cP at -35C. this means, if true, that it passes 0W. 10W just requires less than 7000cP at -25C. Is this a misprint? Anyway, with a VI of 170 it is unlikely that the RS will even pass 10W; I’d like to try it on our test apparatus.

In any case, even hot-running engines do not need SAE 60 oil these days. (by ‘hot’ I mean 120-130C). remember, SAE 60 is heavier than most SAE 90 gear oils. If an oil is too thick, it de-aerates slowly, leading to cavitation in the oil pump, or the bearings being fed slugs of air along with the oil.

Pro-S 10W/50 would be ideal for 300ZX engines. ( a shear-stable xW/50 that stays at 50 is better than an xW/60 that doesn’t!)

 

Regards, JR.

 

UNQUOTE:

 

I've agreed to send him a sample from my stock and he will let me know what he finds!

 

Of course, I will publish the results here or make them available to interested parties depending on how sensitive they are ;)

 

Cheers

Simon

Interesting stuff, keep it coming :)

main advantages of synthetics are they are thinner at high temps, take longer to degrade (if enough additives added) and have lower volatility.

 

as turbos cook oil slowly, best to change oil often, which makes synthetics expensive and probably not cost-effective, as you will be changing them before the oil is past it's useful life in a 'normal' car.

 

No matter how stable or good an oil is, it WILL accumulate dirt/soot/acid/fuel, so frequent changing is the main issue with a turbo. Oil quality is secondary IMHO, assuming it has the right viscosity.

 

Synthetics have been developed for lazy ppl who don't want to change their oil more than once a year - but turbo cars require 6-monthly changes at least.

 

Better to put cheaper oil[but not real cheap cr@p] in 4 times a year than high quality expensive once or twice IMHO.