Your volvo is actually a GM 4.3L engine. Merc uses the same engine and they
recommend straight 30w oil. That is all I have ever used in any I/O engines
I have owned. 40 weight sounds thick to me for your area. 15w50 definetly
sounds thick for your area. Use straight 30w oil in a reputable brand
(Penzoil, Castrol, etc..)

As for the outdrive - you are talking two different things. The outdrive
gear oil is 90 weight. Use marine lower unit oil.
The trim system uses standard motor oil 10w30 as the manual says.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
"Big Daddy" wrote in message
ups.com...
Volvo 4.3L gas engines, 1993. The manual says to use 15w50 oil but the
dealer says that the manual's outdated and now everyone uses straight
40 weight. I'm in the northeast so water temp and air temp changes
from lows in the 40's to the very warm summers.

Also, Volvo 290 duoprop outdrives, manual says 10w30, dealer says 90
weight?

Now I'm confused.

Any ideas? I'm leaning towards the Volvo manual and use what I've used
for years per the specification.