The Advantages of Synthetic Oils over Mineral oils

oilman Jun 21, 2013

  1. oilman

    oilman Well-Known Member

    The Advantages of Synthetic Oils over Mineral oils

    Extended oil drain periods
    Better wear protection and therefore extended engine life
    Most synthetics give better MPG
    They flow better when cold and are more thermally stable when hot
    Surface-active meaning a thin layer of oil on the surfaces at all times (in ester based oils)

    How Synthetic oils Achieve these Benefits

    Stable Basestocks
    Synthetic oils are designed from pure, uniform synthetic basestocks, they contain no contaminants or
    unstable molecules which are prone to thermal and oxidative break down.
    Because of their uniform molecular structure, synthetic lubricants operate with less internal and
    external friction than petroleum oils which have a non-uniform molecular structure.
    The result is better heat control, and less heat means less stress to the lubricant.

    Higher Percentage of Basestock
    Synthetic oils contain a higher percentage of lubricant basestock than petroleum oils do.
    This is because multi-viscosity oils need a great deal of pour point depressant and viscosity improvers
    to operate as a multigrade.
    The basestocks actually do most of the lubricating. More basestocks mean a longer oil life.

    Additives Used Up More Slowly
    Petroleum basestocks are much more prone to oxidation than synthetic oils. Oxidation inhibitors are
    needed in greater quantities in petroleum oils as they are used up more quickly.
    Synthetic oils do oxidize, but at a much slower rate therefore oxidation inhibiting additives are used up
    more slowly.
    Synthetic oils provide for better ring seal than petroleum oils do. This minimizes blow-by and reduces
    contamination by combustion by-products. As a result, corrosion inhibiting additives have less work to
    do and will last much longer in a synthetic oil.

    Excellent Heat Tolerance
    Synthetics are simply more tolerant to extreme heat than petroleum oils are. When heat builds up
    within an engine, petroleum oils quickly begin to burn off. They are more volatile. The lighter
    molecules within petroleum oils turn to gas and what's left are the large molecules that are harder to
    Synthetics have far more resistance as they are more thermally stable to begin with and can take
    higher temperatures for longer periods without losing viscosity.

    Heat Reduction
    One of the major factors affecting engine life is component wear and/or failure, which is often the
    result of high temperature operation. The uniformly smooth molecular structure of synthetic oils gives
    them a much lower coefficient friction (they slip more easily over one another causing less friction)
    than petroleum oils.
    Less friction means less heat and heat is a major contributor to engine component wear and failure,
    synthetic oils significantly reduce these two detrimental effects.
    Since each molecule in a synthetic oil is of uniform size, each is equally likely to touch a component
    surface at any given time, thus moving a certain amount of heat into the oil stream and away from the
    component. This makes synthetic oils far superior heat transfer agents than conventional petroleum

    Greater Film Strength
    Petroleum motor oils have very low film strength in comparison to synthetics. The film strength of a
    lubricant refers to it's ability to maintain a film of lubricant between two objects when extreme pressure
    and heat are applied.
    Synthetic oils will typically have a film strength of 5 to 10 times higher than petroleum oils of
    comparable viscosity.
    Even though heavier weight oils typically have higher film strength than lighter weight oils, an sae 30
    or 40 synthetic will typically have a higher film strength than an sae 50 or sae 60 petroleum oil.
    A lighter grade synthetic can still maintain proper lubricity and reduce the chance of metal to metal
    contact. This means that you can use oils that provide far better fuel efficiency and cold weather
    protection without sacrificing engine protection under high temperature, high load conditions.
    Obviously, this is a big plus, because you can greatly reduce both cold temperature start-up wear and
    high temperature/high load engine wear using a low viscosity oil.

    Engine Deposit Reduction
    Petroleum oils tend to leave sludge, varnish and deposits behind after thermal and oxidative break
    down. They're better than they used to be, but it still occurs.
    Deposit build-up leads to a significant reduction in engine performance and engine life as well as
    increasing the chance of costly repairs.
    Synthetic oils have far superior thermal and oxidative stability and they leave engines virtually varnish,
    deposit and sludge-free.

    Better Cold Temperature Fluidity
    Synthetic oils do not contain the paraffins or other waxes which dramatically thicken petroleum oils
    during cold weather. As a result, they tend to flow much better during cold temperature starts and
    begin lubricating an engine almost immediately. This leads to significant engine wear reduction, and,
    therefore, longer engine life.

    Improved Fuel Economy
    Because of their uniform molecular structure, synthetic oils are tremendous friction reducers. Less
    friction leads to increased fuel economy and improved engine performance.
    This means that more energy released from the combustion process can be transferred directly to the
    wheels due to the lower friction. Acceleration is more responsive and more powerful, using less fuel in
    the process.
    In a petroleum oil, lighter molecules tend to boil off easily, leaving behind much heavier molecules
    which are difficult to pump. The engine loses more energy pumping these heavy molecules than if it
    were pumping lighter ones.
    Since synthetic oils have more uniform molecules, fewer of these molecules tend to boil off and when
    they do, the molecules which are left are of the same size and pumpability is not affected.

    Synthetics are better and in many ways, they are basically better by design as they are created by
    chemists in laboratories for a specific purpose, rather than being modified from something that came
    out of the ground to be as good as they can for a purpose.


  2. fast but dim

    fast but dim Well-Known Member

    interesting read. I ve been using fully synthetic oil im my 120 for 6 monthly oil changes (4k miles ish). I've been concerned that I'm overservicing,and was toying with going to an annual change with full synth, or 6 monthly with a decent semi synth.


    Does the same theory hold true for gear oils? ie synth better?
  3. moggy1968

    moggy1968 Well-Known Member

    but not on an older engine!
  4. Graham

    Graham Well-Known Member I am in uk

    Mine has had the fully synthetic from Toyota from day one.
    Has had 10,000 mile services all it's life.

    Still runs very, very well with close to quarter million miles.

    It gets serviced on miles, and not on time basis.

  5. Rob

    Rob Well-Known Member

    Unless you want to extend the service interval.
  6. wobbly

    wobbly Well-Known Member

    I replaced the mineral oil in the front diff with a Comma semi-synthetic, and it is noticeably louder, so I am going back to a Comma mineral when the seal is re-done tomorrow.

    I used Comma semi-synthetic for lsd in the rear diff.

    I last used Halfords 10w40 semi-synthetic engine oil, changed it to Fuchs from Milners, I *think* its a semi but its actually unclear on the can, engine is quieter, so I reckon on a max of 6000 between oil changes.

    I used fully synthetic oil for older high mileage diesels on my old LJ78, regretted it as it managed to get out of nooks and crannies that the semi didnt.

  7. clivehorridge

    clivehorridge Well-Known Member Supporter Guru I am in romania

    The OP gives such an impressive list of alleged advantages to synthetics that it "smells" somewhat as an all out sales pitch...

    Is there a similarly balanced "disadvantages" list including the real effect on older engines? My HZJ has done 350K km and I'm running on semi. Would I be better off on fully synth or conversely mineral, or should I stick with the semi which seems to perform well up to the change which I do at 10K km (give or take)?

    I'm the eternal devil's advocate I'm afraid, it's my job!

    Thanks in advance of any constructive comments from the professionals, Mr Oilman.
  8. moggy1968

    moggy1968 Well-Known Member

    the only reason you will extend your service interval is because your having to top the oil up so often it's pretty much changed every 5000miles!!

    If you use synthetic oil in an older engine used to mineral you will have problems, one of which will be oil leaks!

    run the engine on what it was designed and tested to run on. Older engines were not designed to run on synthetic oil.
    Last edited: Jun 26, 2013
  9. moggy1968

    moggy1968 Well-Known Member


    generally, stick with what the engine is used to, especially at the sort of mileage you are talking about. If you want to run synthetic you need to use it from new really.
  10. clivehorridge

    clivehorridge Well-Known Member Supporter Guru I am in romania

    Thanks for this advice, I'll probably stay with my trusted semi... :icon-biggrin:
  11. Rob

    Rob Well-Known Member

    I ran fully synthetic for 12k miles in my 1HDFT on a genuine filter with 150k very hard miles on it and not a single oil leak, also tested it afterwards and the oil was like new. I did a similar test with semi and a Bosch filter over 6k miles at around 165k miles and the oil was in much worse condition that the fully synthetic stuff. Both were used in very dusty conditions.

    IMO if your engine leaks with sully synthetic then the seals are on their way out anyway and should be replaced.
    Last edited: Jun 27, 2013
  12. Towpack

    Towpack Well-Known Member Supporter I am in england

    It has nothing to do with older engines not being 'designed' to run on synthetic. An engine is 'designed' to run on oil within a certain viscosity range, be they synthetic or mineral. Synthetic generally has a much higher detergency and will remove deposits and crud from seals and gaskets. In high mileage engines, especially those with a poor service record, these deposits are contributing in no small amount to the oil-tightness of the engine so when new oil flushes them out you have a sieve.
  13. moggy1968

    moggy1968 Well-Known Member

    I understand what your saying about the viscosity rating of the engine.
    I have heard of lots of people who have run engines used to running on mineral swapping to sysnthetic and having problems with leaks. I'll stick to mineral in my HJ60, and change it regularly, and synthetic in my 2012 hilux thanks:romance-kisscheek:
  14. goodoldboy

    goodoldboy Well-Known Member

    ive just been offered a deal on Fuchs titan syn mc synthetic engine oil from my local Toyota dealer.It works out at 45 euros for 10 L VAT included , a great price.The engine is showing 206 K & is a well looked after motor , it came with a FSH & has had a new filter & oil every 6 months since ive had it.Its a oil tight motor & hardly uses anything between changes.Its been on Toyota 10 w 40 semi for the last 80 K miles.Any thoughts?
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