"ransley" <Mark_Ransley@yahoo.com> wrote in message
news:d176291a-d184-4d95-8dc8-b4abf4cfdbcb@p10g2000prf.googlegroups.com...
On Oct 9, 8:34 am, Retired VIP <jackj.extradots....@windstream.net>
wrote:
> On Thu, 9 Oct 2008 04:31:11 -0700 (PDT), ransley
>
> <Mark_Rans...@yahoo.com> wrote:
> >Anybody try it, Mobil site says it can be used where 5-30 is used,
> >wont void warranty, has same hot temp lube properties and saves 2% on
> >gas, I am going to try it.
>
> I ask myself "How can a 0w30 or 5w30 save gas compared with a 10w30
> oil? Please follow my reasoning.
>
> The 'w' stands for 'winter' and is a measure of how fast the oil flows
> at cold temperatures. The second number is how fast it flows at
> operating temperatures. The shear factor is closely related to the
> flow rate so a 30w oil has a higher shear factor than a 10w oil,
> meaning that the 30w oil will offer better lubrication and engine
> protection at operating temperatures. An engine with better
> lubrication will have less internal friction and use less fuel
> overcoming it's internal friction.
>
> If the above is true then it stands to reason that 0w30, 5w30, 10w30
> and straight 30w oil would all give about the same lubrication at
> engine operating temperatures. The differences would show up at a
> cold start with 0w30 giving slightly better engine protection upon
> start up than 10w30.
>
> Since your engine only operates at reduced temperatures for a very
> short period of time, the differences in fuel mileage between the
> different oils should be barely noticeable. This assumes that you are
> in the lower 48.
>
> I'm not trying to be a smart-ass, I really would like to know if I'm
> missing something here.
>
> Jack

In switching from 10-30 M1 to 5-30 Mobil1 years ago my milage and
power went up noticably, I see what you are saying but it doesnt work
that way and I dont know why, Mobil is stating an improvement of 2%
and I believe it even though hot running film strength is about the
same as 5-30, Id say in reality at 170f its still thinner but film
strength is better.