M1 15w50: Minimum use temperature?

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335
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Detroit (Rock City)
Pour point is listed as -45C; I like this oil in my turbo Miata because anything thinner gets burned up. I do drive it some in the winter time, but never when it's nasty out and if it's really cold I'm just as likely to take the Audi which has better heat. How low (ambient temp wise) can I go with this oil? TIA, Robert
 
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College Dorm...
quote:
Originally posted by porterdog: Pour point is listed as -45C; I like this oil in my turbo Miata because anything thinner gets burned up. I do drive it some in the winter time, but never when it's nasty out and if it's really cold I'm just as likely to take the Audi which has better heat. How low (ambient temp wise) can I go with this oil? TIA, Robert
Sorry, sir, but there's not correct answer for your question. Basically, you have a guideline: When it gets real hard to start and you notice noise...
 
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749
Location
98245
quote:
Originally posted by porterdog: Pour point is listed as -45C; I like this oil in my turbo Miata because anything thinner gets burned up. I do drive it some in the winter time, but never when it's nasty out and if it's really cold I'm just as likely to take the Audi which has better heat. How low (ambient temp wise) can I go with this oil? TIA, Robert
That pour point is lower than most 5w30 dino oils. That's to be expected, as synth oils flow well when cold. But what really matters is the minimum pumpability temperature. Just because the pour temperature is lower, doesn't necessarily main the pumpability temperature is lower.
 
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2,480
According to my owner's manual (1994 BMW) and other Euro manuals out there, you can safely use a 15W down to -20C. It then states that this is just a guide, and that the temperature can go above or below this for short periods. If you're referring to M-1, it can probably go colder since it is a synthetic and these numbers refer to conventional oil. Look at Mobil's "max. cold pumping" figures. I believe it's -35C for their 15W-50. This is the coldest temperature that the oil pump can maintain adequate oil pressure.
 

porterdog

Thread starter
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335
Location
Detroit (Rock City)
quote:
Originally posted by TooSlick: That would be for a generic 15w-xx oil, but you can of course go lower with 15w-40 and 15w-50 synthetics, since their BPT's are going to be in the -20F to -35F range....
Thanks for the replies, all! Couple more q's: 1. What's BPT stand for? B(lank) Pumping Temp? 2. Can we generalize the span between pour point and the pumpability limit? I just rechecked, and the pour point is -45C (-49F!). Even if the span is 20C that means that the oil will pump at -25C which is -13F. That should be plenty low enough I think...
 
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22,188
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Colorado Springs
You could also mix 15w-50 with 10w-30 to get a bit better cold pumping and still have a thicker viscosity. I remember someone posted a link to a private Saab repair place in Washington that does that for their customers in winter, and then does straight 15w-50 in summer.
 
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951
Location
Loveland, Colorado
Last winter I ran M1 15W-50 in startup temps down to 12°F. I had no problems, but I'm planning on switching to a 5W-40 Grp3 syn for year-round use in this non-turbo engine in my climate (anywhere between 10°F-100°F startup & operating temps). For our Saab turbo I've been running M1 0W-40 year-round (10k mi interval), but this engine is pretty hard on oil, so at the next change I'm going to mix in some 15W-50 with it. Probably either 25% or 50% 15W-50 (4 qt sump). Is this a stock turbo setup? Do you have any idea how hard it is on oil? (Sorry, I haven't checked the UOA section for postings on this car.) Edit: Here's the Saab flyer mentioning the oil mix. They're in Spokane, so your area, like mine, might get a little colder than theirs does. [ December 08, 2003, 03:52 PM: Message edited by: Eiron ]
 
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Indiana
I mix three quarts of 10w30 and 3 quarts of 15w50 M1 in the winter (gets pretty cold here, at least in the teens and single digits Farenheit) in my 383 LT1 and 2 quarts 10w30 and 4 quarts 15w50 for summer and it seems to work great.
 
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RI
I've used 15w50 in one car year round with no problems. I was always too lazy to use a winter wt oil and didn't care to change it more than necessary. This car has 215k miles and still runs great. I do recommend that you be gentle to the car while it is cold. I also don't see why any other oil weight in synthetic would be a problem even with a high temp turbo.
 

Al

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19,200
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Elizabethtown, Pa
quote:
Originally posted by porterdog: [QUOTE]Originally posted by TooSlick: [qb] Even if the span is 20C that means that the oil will pump at -25C which is -13F. That should be plenty low enough I think...
-13 F is pushing it-as Too Slick mentioned -4F is the rated low pumping temperature. I used the 10W-30 and was able to start at -17F which for a 15W oil would be about -8F. It will probably start at your -13 F . But thats not at all good for the engine and I wouldn't do it unless absolutely necessary. I don't think personally 15W-50 is suitable for Detroit.
 
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5,785
Location
Dixie
BPT for 15w-xx grades is required to be at least -4F/-20C, if not lower ...However, the oil will be pretty thick at the BPT - the Society of Automotive Engineers sets this limit @ 60,000 Centipoise! In order to add a margin of safety, I'd add 15F to that, so I'd say +10F would be good as well ... That would be for a generic 15w-xx oil, but you can of course go lower with 15w-40 and 15w-50 synthetics, since their BPT's are going to be in the -20F to -35F range.... TS
 
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