I would like to know which is the ideal oil weight for a Volvo 940 in florida were it is always hot and cold spells aren't longer than a couple of days, thanks.

 

I live in Texas and run 20W-50 except in the dead of summer when I run 30W. If your car is a turbo, 10W-30 may be better.

 

My car is non turbo and thanks for the help swift.

 

10-30, like it says in the manual

 

The manual also recommends 15w40 for hot weather/severe driving conditions. 15w40 is pretty much the standard issue for class 8 diesel trucks like my old Freightliner, which held 10 gallons of the stuff. I use Mobil Delvac in my turbo, since the engine hasn't been rebuilt yet and does use some oil. Shell Rotella is good, too. If I have an engine that doesn't leak or otherwise consume oil, I use synthetic only; right now I'm running Royal Purple 10/30 in my 240. I have heard people say that you can't run truck oil in a car because the formulation and/or the additives are "different", but I have been doing it for years with no problems/sludge/etc. whatever.
Most big truck diesel engines these days are turbocharged, so it's certainly not going to affect the turbo and besides that it says on the label that it meets the applicable standard for gasoline engines as well.

 

I think all that noise about not running diesel truck oil in cars is based in the higher zinc levels still in diesel oils. They essentially eliminated it in passenger car oils to extend catalytic converter lifespans. I run Rotella T in my 140...it has a flat tappet cam and needs the zinc to reduce wear.

 

Thanks for the Rotella t 15w40 recommendation. I already use that in my gas truck so I will probably start using that in the Volvo as well. It will keep things simpler.

 

20w 50.....unless it gets really really cold then 10w 40.../30. We run 20w 50 in Seattle...

 

Nope...sorry lev....20w 50

 

May be your '88 uses 20-50, 1994 940's use 10-30 according to the Volvo manual (1994 940 Page 8:6).

 

Correct (depending on the temp range).