Sounds unlikely. Tolerances shift with the difference in heat expansion between
unlike materials in the engine - such as rings and cylinder walls. And older
cars such as Merc's which had very fine tolerances didn't specify sewing
machine oil (20W). Fussy people swapped a summer grade (30-50W) for a thinner
winter grade (20-40W) but that probably only made a difference at start up.
Allowing the engine to idle to running temperature before driving off was said
to help and taxis which never cooled down recorded astonishing mileages between
reconditioning - up to three times the norm. But that meant that you were
driving off hard on other assemblies that were still cold such as gearboxes and
diffs! And those have pretty fine tolerances but we're still running 90W in
them are we not?
Then there is the problem of oil exhaustion. As oil ages, even if it is clean,
the hydrocarbon chains are broken down by mechanical damage and it becomes
'thinner' and less viscous. As mean time between oil changes is a lot longer
than it used to be, at least double, then the oil must be a lot tougher or
we're all running on thin stuff.
And the problem of older engines with wear and wider tolerances. Te traditional
approach is to throw in thicker oil but does that really work? Or does it just
make prettier smoke? :-)
It's all too tough for me. I think I'll just do way I always did - stick to
30-50W and wait 30secs before driving off slowly. Seems to work.
Andrew Fildes
afildes@xxxxxxxxxxxxx
www.soultheft.com
Author/Publisher:
The SLR Compendium:
revised edition -
http://blur.by/19Hb8or
The TLR Compendium
http://blur.by/1dQb0sG
On 07/11/2013, at 7:54 PM, Wayne Harridge wrote:
> I understood that in modern engines the tolerances between the moving parts
> was smaller and as a consequence the oil could be less viscous, in fact
> needed to be less viscous to work properly.
--
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