Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Synthetic oil properties

  1. Dec 12, 2006 #1
    We have read that synthetic oil protects and preserves internal combustion engines much better than does natural petroleum. I have proven that to myself over many years in my own vehicles. A question first came to mind the last time I bought synthetic oil...I noticed that it is so much lighter in weight per volume than petroleum that it begs a question ....is at least part of the reason little to no wear occurs in an engine using synthetic oil due to more of the synthetic material remaining on the moving components after operation ceases and the engine cools, at least partially due to the lower gravitational pull on the lighter sythetic oil allowing it to remain on moving components better than heavier petroleum? If so, it would logically provide superior cold start-up lubrication, the lack of which is the cause of most engine wear.

    Thus, is the superior protection of synthetic purely due to its superior lubrication qualities, or does it possibly involve other factors such as the above?

    Thanks for informed responses.
    Last edited: Dec 12, 2006
  2. jcsd
  3. Dec 12, 2006 #2


    User Avatar
    Science Advisor
    Gold Member

    Hmm, I don't know how informed my response is but here goes. I always thought the biggest advantages of synthetic oils were superior stability at high temperatures, and resistance to breakdown, oxidation and other chemical changes with long exposure to heat, exhaust blowby, etc. Most wear to bearings such as connecting rods occurs at high loads and stress (towing a boat or hard accelerations) rather than idling. My favorite auto lube web site explains all this in great detail, although I don't think he addresses the differences between mineral and synthetic oils.
    http://http://www.bobistheoilguy.com/" [Broken]
    Last edited by a moderator: May 2, 2017
  4. Dec 12, 2006 #3


    User Avatar
    Science Advisor
    Gold Member

    Almost certainly not. The density itself doesn't play much of an effect with regard to lubrication. Properties such as viscocity, thermal stability, heat transfer characteristics, ash content etc all have much more of an effect. Obviously some of these will have an effect on density, but the density itself is not a critical property of a lubricating oil.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook