Robert,
On Wed, 12 Nov 1997 04:28:03 +0100 robert weeks <robert@woozy.com>
writes:
>..... Also someone on the list wrote about getting low oil pressure
readings with Castrol and they were going to switch back to their old
oil. If you are out there or anyone remembers this post, can you tell me
what the author of the post was switching back to?
I can't remember who the poster was, but I believe the comment was that
Castrol 20W50 oil would thin out too much when it got hot and the oil
pressure would drop accordingly. The poster seemed to think that
Valvoline 20W50 oil retained the viscosity and the oil pressure better
when hot.
I think I can agree with that, and more. I've used Valvoline oil for
years. I have generally run Valvoline 10W40 oil in my MGA 1500 engine.
For the trip to Alaska this year, towing a trailer for thousands of
miles, I switched it to Valvoline 20W50 oil before the trip. It seemed
to have a few psi more pressure when cool, about the same when hot. When
getting the oil changed at some commercial quick change places during the
trip, it ended up with Castrol 20W50 oil in the engine. While the
pressure was about the same at higher speeds (same relief pressure), the
idle pressure was noticeably lower when hot, like 25 psi rather than 40
psi.
After the 19,000 mile trip I switched it back to Valvoline 10W40, and the
pressure resumed its pre-trip habits, about 40 psi at idle when hot. The
one-step-better bit is that I think that Valvoline 10W40 holds the
viscosity and oil pressure when hot better than Castrol 20W50. Go
figure.
Barney Gaylord
1958 MGA with an attitude
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