Alan,
I know for sure that on multigrade oils like Castrol GTX 20W50 the polymers
(kind of molecular chains), which are responsible for the attribute
'multigrade', deteriorate with time, turning the multigrade oil into a single
grade oil with a viscosity of the basis oil of the multigrade oil (in your
case 20). This process is sped up when the oil is used, resulting in lower oil
pressure (mainly noticeable when the engine is idling), because an engine oil
with a viscosity of 20 is too thin for our cars when driving in summerly
temperatures.
That said multigrade oil will deteriorate even when it sits on the shelf,
although this process is slower than when it is in use. That's one of the
reasons I use single-graded oil in my engine with enough ZDDP and only little
detergent and little dispersion additives in it. That oil was used when our
engines were designed and the manufacturers had to design the engines with the
attributes of this oil in their mind.
I have a more constant oil pressure since using this oil. Even oil consumption
(caused by burning oil and leaking) and engine temperature dropped down a
bit.
Switching to synthetic is no solution, but YMMV.
Eric
Heinsberg/Germany
123ignition dealership
Its just old dinosaur bones settling to the bottom; I am going to switch to
synthetic...
-----Original Message-----
From: healey.nut@gmail.com
To: Healeys@autox.team.net
Sent: Tue, 6 Feb 2007 2:07 PM
Subject: Oil question
Hi -
I have several unopened quarts of Castrol GTX 20W50 that have been on
the shelf about 5 years.
Yesterday I opened one to satisfy my thirst ... and after pouring it
into the BJ8 I noticed a layer of semi-solid brown goo on the bottom
of the bottle.
The oil color (that I poured out) was a perfect golden brown color so
I think the oil was fine to use but my questions are
1) Is the goo the additives that have come out of suspension or is it
something else?
2) If the answer to 1 is yes... should I have shaken or mixed it up
first before pouring it into the car?
Thanks,
-- Alan
'52 A90
'53 BN1
'64 BJ8
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