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(JAXAshby) wrote in message ...
With all that, I don't see any reason that a 20w-40 or 20w-50
would not be a preferable choice to plain old SAE 20, 30, or 40 which are
all recommended in my 1987 manual.

operating weigh above recommendations can harm seals. thus using 20w-40 in
place of 20w doesn't do any good for lubing upon engine startup and can do some
harm when the engine is warm.

some people are under the mistaken impression that multi grade oils "thicken
up" as they warm up. they don't. they just thin out less as they warm up.

a 30w oil will keep its viscosity over a much broader temp range then
a multi weight oil. this is the reason for this recommendation. they
are also better for heavy load conditions, because once again load
creates heat and a 30 w oil will stick around better.

just to clarify jax a 5w-40 oil is 40 at rest/cold therefore will take
more time to pump anywhere being theoretically 25% thicker then a 30w
oil.
perhaps leave the vitriolic attacks at home for people that are just
trying to help. do some reading on oil viscosities is my
recommendation to you.

manufacturers dont make recommendations for no reason, follow them and
you will never have any trouble.
if you are having trouble finding a 30w oil any volvo dealer will sell
it as a lot of volvo equipment uses that grade.