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  1. #1
    Join Date
    Jun 2007
    Location
    Ireland, Carlingford
    Posts
    432

    Default Engine oil vs transmission oil

    What`s the principal difference between gear oil and engine oil? Can gear oil be substituted for engine oil or vice versa?
    Thanks

  2. #2
    Join Date
    Jan 2011
    Posts
    5,585

    Default Re: Engine oil vs transmission oil

    A lot of gearboxes run on engine oil (in fact the majority of cars use the engine oil to also lubricate the gearbox).

    Not heard of gearbox oil being used in an engine though. I suspect the temperatures might be too high.

  3. #3
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,713

    Default Re: Engine oil vs transmission oil

    The difference is that gear oil contains far higher loadings of additives, including boundary lubricants, ZDTP, anti-foam and many others. But the gearbox design determines what oil is needed, dependent upon tooth loadings and temperatures. So your second question is an impossible one to answer. Some boxes have low tooth loadings, e.g. the small Yanmar ones, whereas others may need highly loaded lubricants and even ATF, which is the highest loading of all.
    Answers to some technical queries at new website http://coxeng.co.uk

  4. #4
    Join Date
    Jun 2015
    Posts
    1,498

    Default Re: Engine oil vs transmission oil

    Quote Originally Posted by Bobc View Post
    A lot of gearboxes run on engine oil (in fact the majority of cars use the engine oil to also lubricate the gearbox).
    I may be being a bit thick/senile, but I've never had a car with shared oils. Except Land Rovers. They distribute their oil everywhere.

  5. #5
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,327

    Default Re: Engine oil vs transmission oil

    Quote Originally Posted by srah1953 View Post
    What`s the principal difference between gear oil and engine oil? Can gear oil be substituted for engine oil or vice versa?
    Thanks
    Often very different viscosity. Gear oils having higher viscosities but see later comment

    Different additives... engine oils contain detergents and acidity neutralisers to combat the contamination from combustion products etc Gear oils may contain additives to combat the high loads and wear in certain types of gear systems. There are different specifications for diesel and petrol engines although many engine oils are suitable for both

    However you will often find gearboxes using exactly the same oil as the engine but I dont think you find many if any engines using gear oil

    The SAE viscosities of engine oils and gear oils are measured at different temperatures so are not comparable ( an SAE50 gear oil does not have the same viscosity as aa SAE 50 engine oil)

    Two stroke oils, automatic transmission oils and hydraulic oils are different yet again

    Use the grade of oil specified by the engine or gearbox manufacturer
    Last edited by VicS; 06-06-19 at 15:48.

  6. #6
    Join Date
    Jan 2011
    Posts
    5,585

    Default Re: Engine oil vs transmission oil

    Quote Originally Posted by anoccasionalyachtsman View Post
    I may be being a bit thick/senile, but I've never had a car with shared oils. Except Land Rovers. They distribute their oil everywhere.
    Some examples:-

    https://www.quora.com/How-do-four-st...em-do-they-use

    Most motorcycle engines share engine oil with gearbox oil, which means the oil has to do a different job than in an engine-only cases.

    To add to this a lot of motorcycles use a “wet” clutch which is submerged in oil too.

    In terms of the engine itself it doesn't really do much special, it will have a normal oil pump.

    The magic happens in the oil, it is specially formulated for the application. It has additives to help the clutch while still maintaining a nice slick surface between the gears. This is why you should never use car oil in a motorbike, and also why the service intervals are shorter on a motorbike. Some bikes have service intervals measured in hours! (The KTM 500 EXC has a 30 hour service interval)

    Fun fact, the classic mini also shares it's engine oil with the gearbox, but as the clutch is “dry” it can get away with normal car oil, albeit with a shorter service interval than a typical car.

  7. #7
    Join Date
    Mar 2009
    Location
    UK, Hamble
    Posts
    520

    Default Re: Engine oil vs transmission oil

    My engine, Volvo Penta 2030D specifies either ATF or engine oil for its (ZF-Hurth) gearbox. When I enquired at the local VP agents I was told to use engine oil. I do not know if this was the best advice but it was not as a result of their stocks as they do sell VP priced ATF.

  8. #8
    Join Date
    Jun 2007
    Location
    Ireland, Carlingford
    Posts
    432

    Default Re: Engine oil vs transmission oil

    Thank you very much for these.
    I wasn't intending using an unspecified oil. It's that there have been problems with the cone clutch on the Yanmar SD 50 Saildrive (which I have). On another forum there were comments suggesting it would be better to use GL4 rather than GL5 gear oil. I can't see whether the Yanmar recommended Quicksilver High Performance Gear Lube is GL 4 or 5.
    Anyway, it got me thinking ...

  9. #9
    Join Date
    Mar 2018
    Location
    Aberaeron
    Posts
    1,615

    Default Re: Engine oil vs transmission oil

    Quote Originally Posted by anoccasionalyachtsman View Post
    I may be being a bit thick/senile, but I've never had a car with shared oils. Except Land Rovers. They distribute their oil everywhere.
    My 1970 Mini Cooper S shared the engine oil with the gearbox as did all the original mini engines, don’t know if the modern BMW Mini’s use the same system.

  10. #10
    Join Date
    Jun 2015
    Posts
    1,498

    Default Re: Engine oil vs transmission oil

    Quote Originally Posted by Bobc View Post
    Some examples:-

    https://www.quora.com/How-do-four-st...em-do-they-use

    Most motorcycle engines share engine oil with gearbox oil, which means the oil has to do a different job than in an engine-only cases.

    To add to this a lot of motorcycles use a “wet” clutch which is submerged in oil too.

    In terms of the engine itself it doesn't really do much special, it will have a normal oil pump.

    The magic happens in the oil, it is specially formulated for the application. It has additives to help the clutch while still maintaining a nice slick surface between the gears. This is why you should never use car oil in a motorbike, and also why the service intervals are shorter on a motorbike. Some bikes have service intervals measured in hours! (The KTM 500 EXC has a 30 hour service interval)

    Fun fact, the classic mini also shares it's engine oil with the gearbox, but as the clutch is “dry” it can get away with normal car oil, albeit with a shorter service interval than a typical car.
    Ahah, I think I knew and had forgotten about the Mini (never owned one and I'm too tall to enjoy driving them). Bikes I certainly knew about, rebuilt quite a few, but car-wise, apart from the A series engine are there any others?

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