Hey everyone. I had a post up a while ago. It came up that I might be using too-thick oil.

I checked the manual last night and it looks like 15w-40 is rated down to around 0F. I never see below 30F here on the coldest nights.

Is the manual's recommendation outdated or not? I really need to change my current oil, and maybe that's why I have a few seconds in the morning where the car idles rather low and doesn't feel like it's hitting on all cylinders until about 5 second after start.
Granted that it's a 27 y/o car with 235 on the clock, "maybe" it's got lower compression dry than wet.

Ideas?

Happy Bricking

Will and Wolf -- here's the excerpt from the Volvo manual from the 940 series, though I can't be sure it applies to the B23.

"SAE 15-40 oil is recommended for use in severe driving conditions which involve high oil temperatures or excessive oil consumption, e.g. mountain driving with frequent deceleration or high-speed driving."

The viscosity table recommends 10w-30 between -20F to 104F ambient temperatures.

Much wear occurs when the engine (and oil) are warming up. Thicker oil flows more slowly through oil galleys and passages.

Chris in NE FL, 1994 945 w/ 166K

Very true. Though they didn't write that about a 250K+ mile piston slappy mil that has to be driven hard to keep up with traffic. :)
And any turbo motor is "severe service" in my opinion.

I also use the Rotella because it goes in my diesels too, less types of oil to buy.

While there are some gains in MPG possibly from a lighter weight oil, especially in the cold months, I've been running anything over 20 years old and over 200K miles (which is to say, all the cars I care anything about :) ), on Rotella 15w40.
I don't sweat it in the 20's/30'sF. Plus it has more (if not enough) zink or whatever it is that old cars like.