Mobil 1 75/90 Question

Discussion in 'Oil' started by ad1954, Nov 20, 2009.

  1. ad1954

    ad1954 Member

    I am new to the HD talking and have been reading all of the very useful posts. My question is the result of the posts on Mobil 1 75/90 gear oil. In my research I came upon the Mobil 1 web site Application for Mobil 1. This is a copy of it.


    Mobil 1 Synthetic gear Lubricant LS 75W-90 is intended for initial fill, topping-off or refilling differentials, final drives, transfer cases and other gear applications where lubricants meeting API Service GL-5 and multi-purpose or mild EP gear lubricants are recommended

    Mobil 1 Synthetic Gear Lubricant LS 75W-90 can also be used in rear axles where API Service GL-4 lubricant is recommended

    Not recommended for automatic, manual or semiautomatic transmissions for which engine oil or automatic transmission fluids are recommended
    Where extended service intervals and warranties are required

    ???????????? I am confused with this Recommendation????????????
    Any clarification would be great
  2. Fourdogs

    Fourdogs Junior Member

    Are you talking about the Mobil 1 V-Twin oil possibly? You wanting it for what application?(Mobil 1 Synthetic Gear Lubricant )
  3. glider

    glider Veteran Member

  4. ad1954

    ad1954 Member

    No I was refering to The application recommendation on their web site for mobil 1 75/90 gear oil.

    Quote (direct from web site) "Not recommended for automatic, manual or semiautomatic transmissions for which engine oil or automatic transmission fluids are recommended ".
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    Not sure I understand your concern or apprehension. Your manual transmission should NOT have an engine oil or automatic transmission fluid used as the gear lubricant.

    Use a high quality (like M1, Redline, Spectro, etc.) 75W90 or 75W140 gear lube rated at GL-5. The Mobil 1 gear lube you are considering is an excellent choice. The only reason to use 75W140 is if you live down here in the South or in another climate that has extended high ambient air temperature during the Spring, Summer and Fall. You will be VERY impressed with the difference using M1!!

  6. ad1954

    ad1954 Member

    If Harley says to use the syn 3 in the tranny is that not engine oil?????
  7. TXMikey

    TXMikey Junior Member

    Ad, I think I understand what you're saying, and have been wondering the same thing as well. You are not asking if the M1 75w90 is a quality product, that has already been established.

    Mobil states you should not use M1 75w90 in an a transmission that calls for either motor oil or transmission fluid. MOCO states we should use Syn3 or HD Formula+, which is either motor oil or transmission fluid.

    Is it safe to use the M1 75w90 Gear Oil in an V-Twin transmission, given these paramaters?
  8. ad1954

    ad1954 Member

    Thanks Mikey You put it so much better than I. I agree Mobil 1 is excellent and I use the 20/50 in my Ultra. I worked for a manufacturer and wrote some tech data in my years. What would be the reason for them not to recommend 75/90 gear oil in the tranny???????
  9. biscuit

    biscuit Junior Member

    Absolutely.Harley want you to use SYN3 so they can sell it to you.It is ADEQUATE for the job,but NOT the best option!The best option for this particular job is a GL5 gear oil,perfect for the chopping,churning and foaming that gears create in oil as they mesh and spin.And a synthetic is the best.Those "created" strings of molecules hang togethor to withstand gear abuse better than a poorly built "semi-synthetic" that SYN3 is.

    Here in OZ,Mobil gear oil 75w 90 has been superceded by Mobil DELVAC.Same thing,just a bit better.Which i run in my 2008 model

    I understand your concerns as i now believe a lot more car makers state ordinary engine oils can be put into the transmissions.I think this is cost cutting and i also believe the oil change intervals are more frequent-sort of like sending a boy to do a man's job!

    Stick with a TRUE GEAR OIL that has the right shear strength and is purpose built for the job.A Harley gearbox is agricultural;like a truck,And trucks use real gear oil.:D
  10. silentflyer

    silentflyer Active Member

    I use the Mobile Syn gear oil, no problems, and I don't send any of my $$$ to Hugo Chavez.....