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Thread: Why 20W-50 Oil

  1. #1
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    Question Why 20W-50 Oil

    Can anyone explain to me why BMW uses 20W-50 oils? Is their a valid reason that 10W-40 is not recommended? "K" bikes are water cooled lower RPM bikes similar to some of the newer cars that run in the 3500 - 4000 RPM range.

    To the best of my knowledge most newer cars run 5W-30, 10W-30 or 10W-40.

    I am just curious since 10W-40 is very common and a lot less expensive. I change oil every 3K.

    Thanks
    Roy G.
    85 K100RT Ol Ruby "Gone but not forgotten"
    02 K1200LTC Hoss "Wrecked on 9/21/14"
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  2. #2
    Registered User lkchris's Avatar
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    Quote Originally Posted by roy
    To the best of my knowledge most newer cars run 5W-30, 10W-30 or 10W-40.

    Most newer AMERICAN cars, that is.

    The difference between the American automotive industry and the German automotive industry is like night and day.

    USA industry switched to combat CAFE (fuel economy) standards.

    At your BMW car dealer, you can find 30W-60 oil, too.

    Mercedes is pretty set on 0W-40, perhaps not for AMG versions.

    There is nothing "cheap" about motorcyling, nor should there be.
    Kent Christensen
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  3. #3
    Miserable Mark MarkF's Avatar
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    20W-50 is good for the temp range most motorcyclists ride. Cars are driven when it's much colder which explains 10W-30 and 10W-40. Just my guess.

  4. #4
    Stressed Member jmerlino's Avatar
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    20W50 isn't that expensive, especially if you buy it by the case (and why wouldn't you? You'll use it eventually.)
    --Joe Merlino - Modified '82 R100RT

  5. #5
    dlearl476
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    >Is their a valid reason that 10W-40 is not recommended?

    I don't have a manual right here at hand but IIRC, 10W-40 only offers protection up to 85˚ or 90˚, according to BMW. I would work this time of year, but I wouldn't run it in the summer. 10W is too thin for startup at 80˚ ambient and 40w doesn't cut it in summer heat.

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    I was told by my BMW dealer locally that 20/50 is good all year round in a Boxer motor due to the "forgiving tolerances" within the motor...hehehe...makes you feel like you are riding a cutting edge technology doesn't it?

    He told me this last year when I bought oil when it was -2 F chill factor. He saw my look of surprise as he switched the 10/40 that I had taken for the 20/50 that he kept on the counter. He said that satement to me along with the comment that if you ride all year long then it is fine, if you store the bike for weeks at a time and the oil gets really thick then it is best to go with 10/40.

    That was his logic as an expert. I have used the 20/50 and it worked great all the way down to a ride in the trails in January at -17 F, no problems. On the other hand I did try some 10/40 this March and I realized that I prefer the thicker oil...it seemed that I heard more of my engine but that was probably my imagination too....lol

  7. #7
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    Thanks All

    I appreciate your responses to my question about why 20W-50.
    Roy G.
    85 K100RT Ol Ruby "Gone but not forgotten"
    02 K1200LTC Hoss "Wrecked on 9/21/14"
    12 R1200RT

  8. #8
    Grateful Deaner's Avatar
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    I had an emergency oil change this weekend, site glass popped out, and the dealer said to use 10-40 this winter then go back to 20-50 in the spring. He also said he didn't recomend mixing the oils and when I asked him why he kind of fumbled through an answer that wasn't very clear.

  9. #9
    K Bikes Complex by Choice cjack's Avatar
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    Quote Originally Posted by pudgypaintguy
    I was told by my BMW dealer locally that 20/50 is good all year round in a Boxer motor due to the "forgiving tolerances" within the motor...hehehe...makes you feel like you are riding a cutting edge technology doesn't it?
    I used to use 5W30 Mobil I back in the late '70s in my R100RS when it sat outside the lab for a whole day at 10 F or so. That way it would start. The oil went thru the engine pretty fast tho, but never had any significant wear issues. Still had cross hatch on the cyl at 60K and quite big end bearings, etc.
    The new K1200S is restricted to no heavier than 15W on the low end because of tolerances in the trans, clutch or some such. We are told to use 10W dino or 15W synth (the new synth from BMW made for the wet clutch).
    BMWMotorcycles, fun when they're running...
    My other bike is a BMW.
    Jack Hawley MOA and RA #224, KE9UW ("Chuck")

  10. #10
    looking for a coal mine knary's Avatar
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    Quote Originally Posted by lkchris
    Most newer AMERICAN cars, that is.

    The difference between the American automotive industry and the German automotive industry is like night and day.

    USA industry switched to combat CAFE (fuel economy) standards.

    At your BMW car dealer, you can find 30W-60 oil, too.

    Mercedes is pretty set on 0W-40, perhaps not for AMG versions.

    There is nothing "cheap" about motorcyling, nor should there be.
    I think this is the most accurate post. Aren't engines designed to use a particular weight motor oil? It would seem that a car would run just as hot as a motorcycle (at least a water cooled one), so the difference might be in the design spec. Yes? No?

  11. #11
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    Quote Originally Posted by cjack
    I used to use 5W30 Mobil I back in the late '70s in my R100RS when it sat outside the lab for a whole day at 10 F or so. That way it would start. The oil went thru the engine pretty fast tho, but never had any significant wear issues. Still had cross hatch on the cyl at 60K and quite big end bearings, etc.
    The new K1200S is restricted to no heavier than 15W on the low end because of tolerances in the trans, clutch or some such. We are told to use 10W dino or 15W synth (the new synth from BMW made for the wet clutch).

    I am sure that it comes down to the same decision as the brand of oil...watever you feel best about. The manuals do specify the lighter grades at the respective temps unlike cars that need the thinner oil for the CAFE mileage etc...and that why I was surprised when the dealer said 20/50 to me in the winter.

    I am sure the K bikes,and maybe the R1200's are built with tighter tolerances than the old 1150 Boxers are, or maybe that is just a perception. either way the changing of oil is the most important thing anyway right?

  12. #12
    Danger: Keep Back 500 Ft FredRydr's Avatar
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    Quote Originally Posted by roy
    Can anyone explain to me why BMW uses 20W-50 oils?
    I asked my service department this question in 1999 when I bought an R1100R. Their response was that 20W-50 is specified for oilheads, as opposed to water-cooled BMW bikes, because of higher operating temperatures of the air-cooled motors. FWIW

    Fred

  13. #13
    dlearl476
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    >Still had cross hatch on the cyl at 60K and quite big end bearings, etc.

    IMHO, the fact that you had your engine apart at 60K speaks volumes.

    Loads of modern cars are designed to run 0w-XX or 5W-XX. Our bikes aren't. Me, I believe the BMW engineers when they tell me to run 20W-50.

  14. #14
    PHILC
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    mobil 1 makes a full synth in 15/50 that should work fine in air/oil heads for all temps

  15. #15
    K Bikes Complex by Choice cjack's Avatar
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    Quote Originally Posted by dlearl476
    >Still had cross hatch on the cyl at 60K and quite big end bearings, etc.

    IMHO, the fact that you had your engine apart at 60K speaks volumes.

    Loads of modern cars are designed to run 0w-XX or 5W-XX. Our bikes aren't. Me, I believe the BMW engineers when they tell me to run 20W-50.
    Well not exactly. My '78 R100RS used a quart of oil every 1K miles from the day one. Oil also came out of the push rod seals, and rear seal (or maybe the oil pump cover). I had been from coast to coast on it anyway. But, at 60K I decided to do the valves and seal it up. Also 3 piece rings were going around as a fix at the time. So we did the rings, new guides, touched up the valves, put in new seals and the oil consumption went to around a quart every 3.5K miles. Acceptable. I rode it to about 93K miles and never a problem and the oil consumption stayed at 3.5K/ quart. I don't think the weight of the oil being 10W or 20W is going to be that significant for most normal climates. If it were, then the loss of viscosity with oil mileage would cause more issues than it does. What is the viscosity of 20W50 after 2K miles?
    BMWMotorcycles, fun when they're running...
    My other bike is a BMW.
    Jack Hawley MOA and RA #224, KE9UW ("Chuck")

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