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The API ( American Petroleum Institute ) provides certifications for engine oil.

Such certifications range from SA for 1930's era vehicles up to the current standard SN. The above linked document from the API lists all grades prior to SJ ( introduced in 1997 ) as obsolete.

For SN it lists:

Introduced in October 2010 for 2011 and older vehicles, designed to provide improved high temperature deposit protection for pistons, more stringent sludge control, and seal compatibility. API SN with Resource Conserving matches ILSAC GF-5 by combining API SN performance with improved fuel economy, turbocharger protection, emission control system compatibility, and protection of engines operating on ethanol-containing fuels up to E85.

I see SJ grade oils still on sale at somewhat cheaper prices, and was wondering if there is any real benefit in using the newer SN oils in a vehicle that was originally designed with the SJ grade oils in mind?

I ask about benefit since it seems to be implied by the above document that the newer grade is reverse compatible with recent, older engines - say anything built in the last 20 years.

  • While this may be semantics, there is API - SN and API - SN + RC. The RC or Resource Conserving is a new supplement to the SN standard. You can read some about it here. There are some bonuses to using the newer SN oils in engines as you speak about. A question though, is are you only talking about benefits for the engine? Most of the oil standards have an environmental impact. – Pᴀᴜʟsᴛᴇʀ2 Apr 19 '15 at 12:02
  • @Paulster2 Yes, I'm talking about benefits for the engine. – Robert S. Barnes Jul 20 '15 at 6:39
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SJ is just a new and more developed type of oil, it has more additives and cleaning agents and such. Do you have to buy it for a car designed to take SJ? no. It is completely up to you whether or not you want the SN or the SJ oil. Just whatever you do, do not go any earlier than what your vehicle was designed for!

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They are "better" in the engines they were designed for. They would be poor in the engines of 50 years ago with larger clearances and lower temperatures that burned leaded gasoline. As engines have evolved ,the oils ( and API oil tests) have evolved. I used to read test lab oil reports and many of the old additives were aimed at the bromine ( added with the tetra-ethyl lead) and higher sulfur of gasoline of 50 years ago. A present oil would be unsatisfactory under the conditions of 50 years ago.

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