Using M-1 15W-50 all year?

[MolaKule]

Dr. T.,

I would believe the engineers, not CAFE. When has CAFE ever been in the interest of
engine longevity; rather it's there to appease some "greens".

If my engine clearances would allow it, I'd run 15W50 all year, but for all of my engines, 10W30
seems to provide the optimum film thickness and overall economy.

 

[kev99sl]

quote:

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Originally posted by Dr. T:
Just looking at my owner's manual this morning says to use 15W-50 for temps. from -20C (-5F) to 100F. It goes on to say that ambient outside temps. can go above or below the SAE grades for short periods without problems. Now, I believe these numbers were derived with using conventional oils since looking at synthetics such as M-B's specs of Pour point -45C (-49F) and Pumpability limit of -37C (-35F).

Does this mean it's safe to use all year? I'm in Toronto and it rarely gets to below -20C....and even if it did a couple degrees, would it matter?

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Dump some synthetic 15w-50 in there and forget about it. You'll be fine.

 

[Dr. T]

Just one final ques. for you guys...

Since my post was mostly referring to using Mobil 1 5w50, what about turning it around to conventional oils....How can my owner's manual state to use a 15-50 in the temp. range -5F (-20 C) when I look at most conventional oils of this grade, their PP is roughly anywhere from -6 to -11 F (comp. to M-1's at -45F). Isn't this cutting things a little to close? Why would it be OK to use an oil that is 1F from being a solid? Or is the chart referring to synthetic? Or do I need to be aware of the PP for the specific oil I'm using?

 

[TooSlick]

Comparative CCS viscosities:

M1, 15w-50
5234 Cp @ -4F

M1, 0w-40
4300 Cp @ -31F
Approx 875 Cp @ -4F

Note: For every 5C drop in temp, a PAO based synthetic thickens by a factor of 1.7

 

[Dr. T]

Interestingly enough though....Mobil PDS for Mobil 1 15w50 "Global Oils" which I'm guessing are European, etc. list the following specs:

3800 @ -20 C
x @ -25 C (not avail)
114 cSt @ 40 C
17.5 cSt @ 100 C

vs. N. America's

5,234 @ -20°
14,050 @-25°
124.7 cSt @ 40 C
17.4 cSt @ 40 C

Are European oils thinner at low temps than ours? Or are the Eur. PDS outdated (mentions nothing about SuperSyn and the date is 1995!

 

[dragboat]

TooSlick,
thanks for posting the Mobil 1 SuperSyn 15w50 cP's. That oil has less crank pressure than the 5w30 conventionals available correct? All around the 5500- 6000 mark with exception to Phillips Trop Artic which is 4688 at the same temp. It is a group II.

Somethings not right with that 1995 date?

 

[Al]

quote:

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Originally posted by NevadaDesert:
I think it would be safe to use the 15w-50 all year. However I think 5w-40 would be a better choice for such cold weather ( only in the winter ). Here is an interesting link on the subject of high vis. oils for older and high performance cars. Mobile0w-40replaces5w-50InTheUK

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Real good article. Talked about: Mobil ATF SHC is a fully synthetic ATF with Mercon, Dexron and ZF approval. This has shown to give 5 to 6 times product life in severe applications and is used by both TVR and Viper for race transmissions.

George CLS- What is this stuff??? That's not the regular Mobil 1 ATF??

 

[Mark in NY]

Thanks for that UK link on Mobil 1 Al.

I had a 1980 Honda Civic that was run on 20-50 conventional oil until I sold it in 1991.
At the time of sale it had -
-178k miles it,
- consumed just a small amount of oil between scheduled 6 month oil changes.
- the compression measured within ONE PSI difference between cylinders with a spread of TWO PSI between highest and lowest cylinders.
- the oil pressure measured with a mechanical gauge was 40 PSI @ 2000 RPM

20-50 through a decade of New York winters and autocrossing summers, the results speak for themselves.
I am now taking advantage of the newer synthetic technology by using Mobil 1 0w40.
This is why I cast a skeptical eye on claims of "Too thick" or "5-20 will not reduce engine life".

 

[TooSlick]

Dr T,

The relevant parameter here isn't the pour point, it's the Borderline Pumping Temperature or "BPT". This is exactly what it sounds like - the lowest temp at which the oil will pump out of the pan. It's the temperature at which the viscosity of the oil reaches a specified limit, regardless of SAE grade.

If you wanted to be conservative, I'd use a temp that is 10F-15F ABOVE the BPT and use this as a lower limit for the particular oil. The BPT for Mobil 1, 15w-50 is probably in the -30F range, so you could use it down to -15F to -20F.

However, you'll find the car starts even easier and runs better in very cold weather with the M1, 0w-40. The wear rates will probably be lower with the 0w-40 in subfreezing temps, since it flows better while the engine is warming up.

 

[dickwells]

Back when we used to have "winter" up here in Northern Illinois I decided to run 15-50 M1 in my GMC truck/350 and see how far it would go. At -20F she would not start. When it warmed up to -10 it popped right off. There is a wall that one may or may not encounter depending on whether this trend continues. On the other hand, with 5-30 M1 it started at -30F. Of course I could not go anywhere for half an hour because the oil in the manual transmission was so thick that it killed the engine if I tried to let out the clutch in neutral! That would have been with the grade before trisyn. Regards, RW