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  1. #1
    Join Date
    Jun 2019
    Posts
    7

    Default Choosing two stroke oil for outboard

    I am trying to decide which two stroke oil to buy for a 5HP Mariner outboard, and whether I should buy mineral oil, semi synthetic or fully synthetic. I am aware that the oil needs to be TCW3 spec, but all marine two stroke oil meets this spec, so it doesn't help to narrow down the choice.

    Key factors (for me) are:-
    - less smoke
    - doesn't gum up the engine
    - prolonging engine life, or at least, not destroying the engine prematurely
    - not hazardous to the environment

    There is Westway fully synthetic TCW3 oil on Ebay for £25.99 per 5 litres:
    https://www.ebay.co.uk/itm/5-Litre-M...YAAOSwJq1ZZlHY
    Has anyone used this oil, and is it any good? It certainly seems cheap for a fully synthetic oil.

    At the other end of the price scale is Quicksilver Premium Plus, which is £48 for 4 litres. This is a semi synthetic oil, yet is nearly twice as expensive as the Westway fully synthetic oil.

    What 2 stroke oil do you use in your small outboard, and how do you rate it?

  2. #2
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,327

    Default Re: Choosing two stroke oil for outboard

    Any TC-W3 certified oil should be suitable for your small engine but there is no need to buy the Premium Plus grade, Premium grade will be adequate

    I usually use Quicksilver Premium in my 6hp Evinrude because it is readily available. The higher cost of an occasional 1 litre of Quicksilver from a chandlers is peanuts compared with the other costs of owning a boat.

    At 50:1 fuel mix there should be virtually no smoke
    Last edited by VicS; 14-06-19 at 09:25.

  3. #3
    Join Date
    Jun 2008
    Location
    Surrey and Gosport UK
    Posts
    1,528

    Default Re: Choosing two stroke oil for outboard

    I was puzzled by original post as I just pick up the quicksilver stuff for my small outboard but given rate of usage never seems to run out and I did the query thoughts of OP here?

  4. #4
    Join Date
    Sep 2018
    Location
    Wolverhampton, UK Boat: Gosport
    Posts
    118

    Default Re: Choosing two stroke oil for outboard

    I have 2 outboards with very different requirements:
    Tohatsu 9.8 runs well with very little smoke @ 50:1 = Quicksilver
    Seagull Century Plus uses mineral oil @ 10:1 = any mineral based engine oil.
    I'm sure we're all familiar with the sight and sound of these little workhorses.

    Question:
    I've been told that fully synthetic oil doesn't burn (as in lubricating 2 stroke engines) so how does it get used in outboards?
    I thought the whole idea was to burn the oil/mix as part of the lubrication cycle, without which you'd have an exhaust full of unburnt oil - or am I mistaken?

  5. #5
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,915

    Default Re: Choosing two stroke oil for outboard

    Quote Originally Posted by ashtead View Post
    I was puzzled by original post as I just pick up the quicksilver stuff for my small outboard but given rate of usage never seems to run out and I did the query thoughts of OP here?
    Indeed. 5 litres sounds more like we're talking about sump oil, if that were relevant, unless one is buzzing around 24/7 in the dinghy.

    Richard

  6. #6
    Join Date
    Nov 2009
    Location
    Home UK Midlands / Boat Croatia
    Posts
    18,915

    Default Re: Choosing two stroke oil for outboard

    Quote Originally Posted by Oletimer View Post
    Question:
    I've been told that fully synthetic oil doesn't burn (as in lubricating 2 stroke engines) so how does it get used in outboards?
    I thought the whole idea was to burn the oil/mix as part of the lubrication cycle, without which you'd have an exhaust full of unburnt oil - or am I mistaken?
    Synthetic oil does mechanically break down at a higher temperature than mineral oil but at combustion chamber temperatures all types of two-stroke oil will burn.

    Richard

  7. #7
    Join Date
    May 2001
    Location
    North Wales, sailing Aegean Sea or Menai Strait
    Posts
    21,712

    Default Re: Choosing two stroke oil for outboard

    Mineral oils are hydrocarbons comprising a mixture of molecular weights, the heavier ones tending to form gummy deposits in high performance 4 stroke engines.
    Synthetic oils are 'built' from gases and light liquids and thus the range of molecular weights is far narrower than in distilled oils. Otherwise they are the same thing, so will burn in a 2 stroke
    Answers to some technical queries at new website http://coxeng.co.uk

  8. #8
    Join Date
    Sep 2018
    Location
    Wolverhampton, UK Boat: Gosport
    Posts
    118

    Default Re: Choosing two stroke oil for outboard

    Quote Originally Posted by vyv_cox View Post
    Mineral oils are hydrocarbons comprising a mixture of molecular weights, the heavier ones tending to form gummy deposits in high performance 4 stroke engines.
    Synthetic oils are 'built' from gases and light liquids and thus the range of molecular weights is far narrower than in distilled oils. Otherwise they are the same thing, so will burn in a 2 stroke
    So, if I understand you correctly, I can switch 'Smokey Joe' onto a cleaner burning mix? But would it still need 10:1 or do you think that could be eased out to say 20:1 or less?
    Cheers
    George

  9. #9
    Join Date
    May 2007
    Posts
    36,745

    Default Re: Choosing two stroke oil for outboard

    Quote Originally Posted by RichardS View Post
    Synthetic oil does mechanically break down at a higher temperature than mineral oil but at combustion chamber temperatures all types of two-stroke oil will burn.

    Richard
    Combustion chambers contain a big range of temperatures, the spark, the flame, the plug electrodes, piston and cylinder wall will all be different.
    Better oil might well be changing less on the cylinder wall.

    Unless you've got a 60HP outboard, the amount of oil is so small, might as well buy known good stuff.

  10. #10
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,327

    Default Re: Choosing two stroke oil for outboard

    Quote Originally Posted by Mustardrat View Post
    I am trying to decide which two stroke oil to buy for a 5HP Mariner outboard, and whether I should buy mineral oil, semi synthetic or fully synthetic. I am aware that the oil needs to be TCW3 spec, but all marine two stroke oil meets this spec, so it doesn't help to narrow down the choice.
    I am suspicious of the statement that the Westway oil in question is TC-W3®

    It does not appear on NMMA's list of TC-W3® certified oils

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