I recently picked up a '94 945 with 117K miles. In an effort to sort through cold-start problems, I've changed from the recommended 5w-30 dino to Mobil 1 0w-40. Perhaps Herr Ludwick or others can offer opinions on using 0w-40 synthetic. It's not in the recommended range of viscosity listed in the owner's manual. Bear in mind the car is in Vermont, and we've been enjoying two of Canada's favorite exports: Molson and -25F nights!
chris of the frigid north. 244, 765, 945, r100rs, etc.

0-40 Mobile 1 should be fine year round.
I run 0-30 amsoil full synthetic year round in both of my gas burners, in Arkansas.
It's not going to get too hot for it up there. Remember, synthetics don't start getting freaky in the heat anyway, I've been through death valley on synthetic at over 125deg f outside with no pressure drop.I seriously doubt that you'll encounter anything even close to that up there.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel

I'm curious why you opted for 0W-30 and not 10W-30 as the manual suggests. Especially in warm Arkansas.

I am trying to learn about advantages/disadvantages of using differing weights especially if one is using synthetics.
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Paul NW Indiana '89 740 Turbo 108,000

You can use a 0W-30 anyplace that a 5W- or 10W-30 are recommended. All will be in the same viscosity range at operating temperature. The 0W- will pump up faster when cold.
The AMSOIL 0w-30 generally gives better fuel economy than the AMSOIL (or other) 5W- or 10W- and is a stronger oil.

re: I've been through death valley on synthetic at over 125deg f outside with no pressure drop.

Of course not. Your thermostat is set at 180-190deg and therefore 125deg is nothing.

Now, if you were pulling heavy weight up a steep hill at 5mph ... Heat generated in an engine is directly proportional to engine rpm, and road speed has some effect on heat transfer to ambient air, but temp of that ambient air has little to do with it because it's never close to engine temp.

It's really only the left side of those viscocity recommendation charts that's important, because temp of the engine when not running is truly affected by ambient air temp and nothing the engine designer can do can affect that. However, the engine designer has all kinds of control over the temp of the engine when it's running and can quite easily overcome any challenges posed by ambient air temperature.

A LOT of engine designers these days are specifying ONLY synthetic oil, and 0W-40 is about the best there is. Best article on synthetic oil is
http://www.canadiandriver.com/articles/pb/synthetic.htm

Hey guys, I just wanted to weigh in here and let you know an observation of mine. I decided this fall that I'd try 15W40 in my B230F because it has some slap when cold, I drive it hard sometimes, and diesel oil has preferable qualities. The manual says it's ok for severe conditions (towing, extended hwy driving, etc). So I did a little research and decided to try Shell Rotella-T 15W40. I had been running 10W30 dino and I believe that's what the previous owners used. Well, it seems to love the Rotella! It apears to run smoother and quieter. The oil consumption is around 3/4L every 5K km which I think is pretty good for 362K (~226K mi) on the odo. Anyway, my real point is that it's been below -15C almost every night this week and close to that during the day. Around -18 last night and -20 tonight. Every morning the coolant heater gets plugged in for ~2 hours before I start the car. From all I can tell it starts pretty normal (other then a slipping belt and a little slow at first due to the cold battery). No noticeable valve sounds due to lack of oiling or anything like that. The manual says that 15W40 shouldn't be used below -15C, but I have yet to notice a problem (knock on wood). I just thought I'd let you guys know. My Volvo mechanic always says thicker oil is better (to a point of course) and he doesn't like to use 5W30 or anything lighter. I use Amsoil 10W40 in my B230FT, but thought it was pretty interesting how well the dino 15W40 works in the B230F. It's due for an oil change within the next week and I see no reason not to put fresh Rotella in.....What great cars :)
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Chris. Halifax N.S. '91 745Ti, 287K km and '91 745 NA, 362K km.

If it were a 960 series, I would highly recommend the 0W40 weight Mobil 1. These are more demanding and less forgiving engines. MB uses 0W40 in all their cars. I ran 10W30 in both my 240s and was fine. I'm not sure that the 0W40 is necessary for a 4 cylinder, but it probably won't hurt it....
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John Shatzer, '97 V90 @ 105K

My 2 cents:

5w-30 in the winter, 10w-30 in the summer.

0w-30 if it's REALLY cold, but a 30 gap is larger than i'd like to run on dino.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

In my opinion the M1 0W-40 will be just fine. I run it in our two 960/S90's year round. We go down to -teens F in the winter here and 95+F in the summer. No worries with the 0W-40. It's a very good oil.

DEWPFO
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1998 S90 066,800 and 1995 964 150,200

Dear zimmiefan,

Good p.m. and may this find you well. Ich heisse mich nicht "Herr Ludwick" und Ich kann ihn nicht! Glad to hear you're using Mobil1.

I used to live in the Midwest, and so met with temps comparable to yours in Vermont. I ran 5W-30 in a 240 series car in the winter, and switched to 10W30 in the summer.

A lighter weight oil makes sense in extreme cold: it will be less viscous and so get to where its needed faster. It will also ease strain on the starter/battery.

That said, I would not run 0w-40 in the summer: it is too thin for the heat of a Vermont summer. I would switch to 10W30 about 1 April and keep it in until 1 December, or a tad later.

I use Mobil1 10W30 year-round, here in the northeast, as my car is almost always garaged. As a result, the block temp does not drop to ambient.

Hope this helps.

Yours faithfully,

spook

>>>That said, I would not run 0w-40 in the summer: it is too thin for the heat of a Vermont summer.

Why would it be too thin? At operating temperature, or around 210F, it would be in a 40 visocity range, which means it is thicked (or more resistant to internal flow) than a xW-30.