Synthetic oil for I-5s

[Bo Young]

That reminds me of a question that's been bugging me for a while.  Does
anyone know what percentage of an engine's heat comes from friction as
opposed to combustion?

If a synthetic oil has a lower coefficient of friction (is more 'slippery'
than) dino oil, then the engine will generate less heat from friction, but
that only makes a difference if a significant percentage of heat comes from
friction.

----- Original Message -----
From: "Robert Deutsch" <rdeutsch at sk.sympatico.ca>
To: <quattro at audifans.com>
Sent: Tuesday, August 19, 2003 1:50 PM
Subject: Re: Synthetic oil for I-5s


> David, I'm just finishing up my mechanical engineering degree and I've
> been talking to the profs at school lately about this.
>
> First off, synthetic oil may not give you any cooler oil temps (the only
> way it would be cooler is if the oil had higher conductive and
> convective heat transfer coefficients - which would probably be
> negligible - and then the limiting factor still remains the heat
> transfer properties of the engine block, valve cover, and oil pan).
>
> As far as changing from synthetic to dino oil, there is no compatibility
> issues whatsoever. You can run a mixture of the two if you like. The
> synthetic molecules all being perfectly uniform in size however, gives
> you a better chance of leaks; whereas the dino oil has a range of
> molecule types and sizes which can build "beaver dams" around areas of
> potential leakage. If you suspect leaks, you should use the highest
> viscosity synthetic oil you can find (ie: the higher the first number
> the better - 10 from 10w30 for example). Watch out for oils like 5w50
> synthetic. When cool it acts like 50 weight oil, but when up to running
> temps it acts like 5 weight (really thin). Try to find 15w- or 20w-
> synthetic oils for higher viscosity at high temperatures.
>
> As Jim mentioned, if heat is seriously a problem, the only way to
> properly deal with the heat is with an oil cooler. This is an additional
> radiator that will remove the excess heat directly from the oil.
>
> I personally just had to go back to dino oil as I couldn't find
> synthetic thick enough and my valve stem seals are starting to fail. I
> went back to 20w50 multi-grade and it has resulted in less blue smoke.
>
> Rob Deutsch
> '90 CQ20v 200k
> '01 Beetle Turbo Sport 20k
>
>