Using M-1 15W-50 all year?

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May 28, 2002
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?
If your manual says you can use 15W-50 down to that temp, I don't see why you can't use it all the time. Although I don't necessarily think it's optimal. Chances are you would see better overall performance from a 0W/5W-30/40 oil. Less viscosity speeds oil circulation at cold startup, and there are very few street cars (modified or not) that need a xW-50 oil anyway.
`94 BMW. This past winter I can only remember -18C or so...but I'm sure -20 isn't too far off...but if M-1 still pumps at -37C, why not use it all year round? How cold is one's freezer...I want to test this out...
Originally posted by Dr. T: `94 BMW. This past winter I can only remember -18C or so...but I'm sure -20 isn't too far off...but if M-1 still pumps at -37C, why not use it all year round? How cold is one's freezer...I want to test this out...
I've done freezer tests on more oils than I can remember (20F freezer). Even though its pourpoint is that low, it is still very, very thick at those temps. A 5W and a 15W with equal pourpoints will not behave the same at 20F...I have seen this firsthand. Just because it can move at that temp doesn't mean it will move well.
I find it amusing that owners manuals don’t mention any difference between dino and syn recommendations. I use M1 15w50 year round. Sometimes I find myself in Idaho in January or southern Nevada in July. If I were using dino oil I would change grades between winter and summer. But IMO, I think M1 15w50 can handle the temp range I drive in. If I lived in Canada I might consider a syn 10w40 since it’s a not likely you’ll be in the Mojave desert in July.
I don't remember it even getting down to -18C here in Toronto last year. And if you park in your garage overnight anyways, your car may never see those low temps. But why would you want such a thick oil anyways? It doesn't get that hot here (95F is about the hottest it gets, but typical summer days are 80-85F) and that thick oil will just rob you of power and MPG.
I average 36 mpg using M1 15w50. How much more mpg do I need? Power? I hop on my bike when I feel like doing 11 sec 1/4 miles. I agree that 10w30 will handle most needs for cars. But is it the best oil for longevity? Why is 40 or 50 weight oil too thick? Cold start up? Too high HT/HS viscosity? Oil filters going into by-pass mode too often? Too many questions, not enought time and money to figure it out.
With the 15W-50 you are wasting horsepower, creating unwanted heat. You just do not need that thick an oil for your engine. You might consider the Mobil 1 0W-40 or 10W-30, year round.. They will work superbly and you will have a win/win with respect to fuel consumption, power, operating temps. George Morrison, STLE CLS
Ny son has a Mercedez straight six and it recommends at least 10W40 for winter and 15W50 for summer. We had used Amsoil 15W40 AME in the winter and Mobil 1 15W50 in the summer, and now he uses Mobil 1 15W50 all year tround; his average fuel mileage has increased by 1 mpg and his operating temps in summer has dropped about 3 F.
satterfi At leat you know 15W50 will do the job. As I mentioned the other day somebody in the U.S with a Volvo S40 turbo is using 10W30 I think? Shell Australia's rec for the identical vehicle is Helix Ultra 15W50 syn and BP say Visco 5000 5W40 syn. Which engine will last the longest I wonder?????
What I really wish we had on the internet somewhere, was a list of all the high mileage cars out there (such as Irv Gordon's 2,000,000 mile Volvo) and what oil and viscosity they run. I just don't think a thick oil is needed in order to prolong an engine. Didn't that 1 million mile 94 GM Truck run nothing but 10w30?
If the manual says it's ok to run 15W50, run it, but just because it will pump in the winter does not mean I'd run it in the winter. A 0W40 or 10W30 will still pump a lot better. What does the manual say about other viscosities? Please don't give just one data point. When I post what a manual says about viscosity choice, I post everything it says.
DrT, Unless you are having oil pressure and/or oil consumption problems, I'd also recommend running the mobil 1, 0w-40 year round. The engine will run cooler and you'll get better performance and fuel efficiency. running a 50wt oil in very cold weather is completely unnecessary .... Tooslick
I don't think you're going to manuals recommend heavier weight oils due to pressure from the EPA. You used to see charts like this in car owners manuals. You still do in bike owners manuals because they can recommend what they think is best without outside influence.  - [ September 07, 2002, 10:06 AM: Message edited by: satterfi ]
This chart is approximately what my owner's manual guys recommending 5-30 all year...the chart here shows it's only recommended for temps up to 5C!!! I'll have to scan mine in, but it shows the 5-30 good up to 10C and 5-40's good up to 20C and the x-50's for 30C and above...go figure... Who do you guys still believe...the automotive engineers or cafe? Why do they make the 15-50 if no engine is supposed to use them (according to half of you guys) because of robbed hp, or fuel economy? Perhaps a certain engine runs best on this grade and that's the for the rest...guess they'll need auto-rx to clean things out....
Dr T, It shows those grades due to the model year of the vehicle ...most of the German manufacturers didn't start recommending low viscosity synthetic lubes until about 1997. Most current German engines now call for 5w-30 or 5w-40 synthetics year round. The engine will start with the 15w-50 in subfreezing weather, but it will be pretty sluggish, especially while it is warming up. I've run the Amsoil 20w-50 synthetic in the winter down here in Alabama (in an Audi), but I prefer to go one or two grades thinner in cold weather. TooSlick
If 40 weight is only recommended to 30C, I would go ahead and run 15W50 year round, but I would also install a block heater for when it got cold. Failing that, I'd run 0W40 in the winter, and as soon as temps got above 30C, switch to 15W50. I believe that specific engines will last longer on certain viscosities, the ones they were Designed to run. I've seen LT1s go to 300k on a steady diet of 5W30, so I know that works. I've also seen engines pack up in short order on 50 weights, so that is definitely not the panacea that some think it is. I do believe that CAFE is responsible for 5W20, but 10W30s were recommended for certain engines long before CAFE came into being. My Yamaha Fazer calls for 20W40. That shows that 50 weight is not called for in all non-CAFE driven applications. This is a very high performance engine, capable of over 133 HP / L (2.1 HP / CI), but still known for being one of the longest lived and most reliable engines in M/Cs. As for needing AutoRx, well, all engines build up deposits, some worse than others, and 50 weights just like the rest. I've seen heavily sludged up engines, run with every viscosity there is. [ September 08, 2002, 04:58 PM: Message edited by: VaderSS ]
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 [ September 09, 2002, 05:32 AM: Message edited by: NevadaDesert ]
Yes, I would not worry about it. I used it year round as well. My analysis is in the forum. The HP, mpg, and heat are a non-issue. We are talking maybe 1-2%. I don't believe cold starting is a problem as much as people make it out to be. That is what esters and other barrier adds are for. I don't switch oils for winter in either of our cars. I think it's pointless, unless you are going to antartica or something. The thermostat controls the temperature of the engine so at operating temp you still need that thicker oil. I have verified this with my OT guage. Less than 10F difference between summer and the coldest(subzero) winter weather. [ September 09, 2002, 10:34 AM: Message edited by: Jason Troxell ]
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