correct oil level?

Discussion in 'Airheads' started by mslim, Oct 10, 2021.

  1. mslim

    mslim Long timer

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    OK I have an R90S with a deeper oil pan. It initially came with the OE dipstick but I was worried about maintaining the correct oil level so I bought a longer later model dipstick.

    With the longer dipstick I've been trying to keep the oil level halfway between the min and max markings. Is this the correct thinking or should I just keep it near the max level?
    #1
  2. bmwrench

    bmwrench Long timer Supporter

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    I fill to the "MAX" line, and don't add until it drops to "MIN".
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  3. radmann10

    radmann10 Old fart Supporter

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    Warm up the motor, 30 min ride stop, let set for a minute or two check oil. I fill to the top/max mark, as it will decrease as you put miles on the bike.
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  4. 100RT

    100RT Long timer

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    Here is the original dip stick (deep pan) from my 81 R100RT for reference. Ruler against bottom of filler cap.
    colage dip stick.jpg
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  5. BigWally

    BigWally Been here awhile

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    My R90S will puke out oil above the mark in the pic. BMW put out a tech bulletin on this back in the day - IIRC it pertained mostly if not exclusively to the R90 series. Paraphrasing: "find the engine's preferred oil level & only fill to that level." That's 2.5L (incl filter) on my bike and it has a deep sump.
    dipstick.jpg
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  6. Plaka

    Plaka Brevis illi vita est

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    Why do you run a deep sump? The answer to that determines how much oil you put in it.
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  7. bmwrench

    bmwrench Long timer Supporter

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    Be aware that there are two different length 'sticks.
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  8. mslim

    mslim Long timer

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    See original post. That's why I went to a longer stick. I got tired of guessing where my oil level was.Note bmwrench's comment above. My dipstick measures the same as the one in 100RT's picture. With the deep pan I usually just put in 2.5L on an oil change.
    It came on the bike when I bought it.
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  9. Kiwiabbo

    Kiwiabbo Long timer

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    There are a couple of lines of thought that go with a deeper sump. 1 run the same level as in use your standard stick and run extra oil in the sump. Levels of thought on the whys to that with cooling and contamination. 2 run the standard amount in the sump with a longer dipstick to check level. Thought I believe are around resistance to oil on the crank and better for the likes of a race motor with less drag on the crank, the important part is to make sure the pick up is tight and the correct length for the sump.
    #9
  10. BigWally

    BigWally Been here awhile

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    AFAIK the deep sump was standard on my ‘76 S. At any rate that sump and the pictured dipstick were on the bike when I bought it. At first oil change I filled to the MAX line and it immediately smoked out the "excess" down to the red line in the pic. Upon researching this further I found the following quote in another post:
    "In 1976 a service bulletin from the factory put oil consumption and levels into a perspective I have never forgotten. Customers who rode the R90S and R90/6 reported initial oil consumption after filling which lowered the level on the dipstick by about a quarter inch in a very few miles. They ALL did it. Interestingly, if one topped the oil off, it blew it right back out. If one left the oil at that level, it stayed there. The factory service bulletin recommended scribing a new line at the level the engine preferred and to fill to that level at future oil changes."

    So on the next oil change I filled to the red line (2.5L) and had no oil immediately smoked out.
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  11. 190e

    190e Long timer

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    Besides the Dec 75 service bulletin that gave specific advice to run 13mm below the max mark on an R90s, there was also an Aug 1990 service bulletin on oil consumption which said:

    Do not add oil until it reaches the min mark on the dipstick... and then add no more than 1 pint. Too much oil results in higher oil consumption at high speed via the engine breather....

    I US pint is approx. 0.5 litres so the bulletin is effectively saying don't run above half way between the min and max marks. I wouldn't be surprised if that also translates to somewhere close 13mm below the max mark.

    I can't post PDF files but if anyone wants copies of the bulletins message me with an e-mail address.


    #11
  12. TwoShoes

    TwoShoes Carbon-based bipedal life form

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    Here is the Dec 75 bulletin that I converted over to a .jpg file to share with others. Thank you 190e! I'd been looking for this bulletin for some time
    bulletin page 1.jpg bulletin page 2.jpg
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  13. TwoShoes

    TwoShoes Carbon-based bipedal life form

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    and here is the Aug 1990 bulletin again from 190e, Thanks Barry!

    page 1.jpg page 2.jpg page 3.jpg page 4.jpg
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  14. BigWally

    BigWally Been here awhile

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    Fwiw the red line on the image of my dipstick is 6mm below the MAX line. YMMV.
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  15. melville

    melville Long timer

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    My R75/6 has a deep sump (MAC or similar) and the OG short dipstick. Three full quarts on a change puts the oil level about halfway between MIN and MAX. It will get to MIN in about 2000 miles. I'll add 1/2 quart and change the oil when it next gets to MIN in another 2000 miles.
    #15