The 20 means it performs as a 20 wt. oil at -25 f limited to 4500 rpm.
The 50 means that at 210 degrees (which is considered a normal warm engine
temp), it has the load capability of a 50 wt. oil.
The cold numbers are a "pourability" number, too.
One further thing: the additives that allow this depletes as the oil is used
because the additive "package" goes away through shearing and other factors,
leaving you with a less effective oil.
A 20w-50 may wind up as a 20w-40. Using group four (4) pao synthetic oil does
away with this problem since they don't have an additive package. This is one
reason they have longer change intervals.
Be sure its a group four synthetic. Other groups may be just a more refined
regular oil with less sulfer in it.
Interesting but not really germane for most of us.
As Randal says, good pressure, enjoy the drive!
Sent from my Verizon Wireless Phone
----- Reply message -----
From: "Randall" <tr3driver@ca.rr.com>
To: <triumphs@autox.team.net>, "Angelo Graham" <agraham@execulink.com>
Subject: [TR] TR2/3 - oil pressure adjustment
Date: Fri, Aug 2, 2013 1:00 pm
---- Angelo Graham <agraham@execulink.com> wrote:
> My '2 had the early filter head with the partial full-flow feature.
Not "full flow" at all, it was a bypass type filter, designed to take wool felt
filter cartridges that wouldn't flow enough oil to feed the engine. So the
engine was fed with oil direct from the pump, and the filtered oil was returned
to the crankcase (to be sucked up the next time). That sounds really bad,
until you consider that many successful engines (eg the Model T and VW bug) had
no oil filters at all!
> My engine seems to be
> running a high oil pressure - around 50 lbs. at idle and going up to
> around 70 - 80 lbs. revving or under load. I feel this is a bit high
That is perfectly normal, I would leave the adjustment alone! Practical Hints
calls for 70 psi minimum with hot oil and traveling at speed. If you would
like to see only 70 psi instead of 70 to 80; try using thinner oil. Assuming
you are still seeing 80 with the oil thoroughly warmed up; without a thermostat
it takes much longer for the oil to get up to normal operating temperature than
shown on the dash gauge. A fresh engine shouldn't need 20W50 unless you
routinely drive in desert conditions. Again Practical Hints only recommends up
to 40 weight. (Note that the 20W portion of your oil's rating refers to its
"winter" performance, below freezing. At operating temperature, it's a 50
weight oil.)
> Do you try to get the adjustment at idle and that should set it for the
> entire range?
NO! The pressure relief valve should only start to open at 70 psi. In the
vast majority of cases, it will not be open at all at idle. And even once it
starts to open, it operates over a range, so the pressure will still not be
entirely constant.
> I have a freshly rebuilt engine with no apparent problems and using 20 -
> 50 oil.
Stop worrying, get in and drive!
Randall
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