A 15w-50 oil is not a thin oil. Getting such a low oil pressure at idle
with an oil of such viscosity indicates a pretty substantial inability to
maintain pressure. Be it from well worn bearings being unable to sustain
pressure to a well worn oil pump unable to build pressure.
That said, oil pressure at idle doesn't have to be much. The old rule of
thumb of 10 psi for each 1,000 rpm is a reasonable rule of thumb. Such a
low oil pressure at idle will send many a sending unit into an illuminating
Why is Mobil 1 in particular creating this scenario? I don't know. There
are lab standards for those viscosity numbers, and I have read articles
showing that many manufacturers do not well adhere to those standards.
Mobil may be doing a poor job of this with Mobil1, but I don't know that as
a statement of fact.
----- Original Message -----
From: "Jim Muller" <firstname.lastname@example.org>
To: "Triumph List" <email@example.com>
Sent: Tuesday, May 05, 2009 10:37 PM
Subject: [TR] oil pressure with synthetic oil
>I know this has been discussed before, but what the heck, if it was
> interesting once it might be interesting again.
> Several weeks ago I changed the oil in the GT6, put in Mobil-1 15w50
> I think it was. I had used it prior to this oil change, something
> labelled "extended life" or similar, but this wasn't labelled like
> that. It used to be that with thin oil I'd hear valve clatter, but I
> don't hear that at the moment. What I am getting though is the oil
> pressure light (and brake light) flickering when at idle after I've
> been on the highway for a while. Given a chance for the oil to cool
> the flickering goes away again. The temp gauge is acting quite
> normal. This behavior started immediately with the new oil and it
> isn't due to gas collecting in the sump.
> It is somewhat disconcerting and I'm tempted to drain it.
> Comments welcome.
> Jim Muller
> '80 Spitfire, '70 GT6+
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