There's an interesting thought. I agree that you want more oil and less
"viscositizers". But is it the difference of high-low or the ratio of
high/low that is more important?
Anybody have any idea?
- GeneG
- www.garrison-grafixx.com/tr6
On Wednesday 24 May 2006 8:47 am, Navarrette, Vance wrote:
> Pat:
>
> 20W-50 would have been state of the art in 1974 and was
> recommended by the factory.
> Times have changed, and technology has moved on. The thinking at
> the time was that higher vis oil was needed to compensate for the
> thinning that occurs during extended driving. This was thought to reduce
> wear by insuring a robust film on moving parts. So far so good.
> Since then, the thinking on engine wear is that the vast
> majority of wear in fact occurs at startup, when almost all the oil has
> drained out of the block into the sump. During extended driving there is
> an ample supply of oil, so the impact of viscosity is small. Because of
> this change in thinking, engine manufacturers are concerned with getting
> oil to the moving parts as quickly as possible at startup, so thinner,
> easier to pump oils are recommended. 10W-30 would be a more modern
> recommendation, some even recommend 5W-30. Add to this the fact that
> there is a small improvement in mileage and HP with lighter oils (less
> work to spin the oil pump) and you have a strong consensus to use the
> lighter oils.
> One other thing to think about; To get an oil to have the
> extended viscosity range that 20W-50 has (a spread of 30 points) it is
> necessary to add a large quantity of viscositizers. Viscositizers have
> inferior lubricating properties, and so degrade the lubricating
> properties of the base stock. 10W-30 spans a smaller range of viscosity,
> and so uses less viscositizers and therefore has superior lubricity.
> This means lower wear despite the lower viscosity.
> You will notice a slightly lower oil pressure when the engine is
> warm if you switch to 10W-30. Do not be alarmed, as it is to be expected
> and does not mean anything is wrong. Quite the contrary, it means better
> mileage and more power (not enough for you to notice, though).
>
> Vance
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