I have only recently started posting on this site, but I have been reading for several years. It seems that the topic of high mileage oils often brings out the most passion in many people.
I work in industrial maintenance. Where I work, we use all Mobil lubricants. I often use Mobil's forum, much like this site, but focused on industrial topics. www.club.mobilindustrial.com
I recently posted a question in the "Ask the Experts" thread. Here is what I asked:
There is a popular motor oil forum called Bob Is The Oil Guy. More than any other topic, high mileage motor oil brings out the most passionate dialog. There are many whom are staunchly opposed to the use of high mileage oil, unless you are having issues. They say that if you put high mileage oil in an engine that does not have any leaks, smoke, noise, etc. you will actually cause damage to the engine. They contend that high mileage oils contain seal swellers that will actually damage many seals over time by softening them too much, etc. They go on to say that in areas that engine manufactures use silicone based sealants rather than gaskets, high mileage oil additives will break that sealant down over time too and cause additional leaks. Then there are those that say the opposite, high mileage oil is fine to use in any engine with no worries. There are also some whom sing praises of high mileage oil saying that their engines had leaks that stopped once they started using high mileage oil. Could we please get some honest, candid, facts from engineers whom know the truth about what is in that oil and all of the different possible outcomes of using it? It would be wonderful to put some of this banter to rest. Thank you!
The response came today from Korey Sargent, Lubrication Support E.I.T in Fuels and Lubricants Marketing at Exxon Mobil. Here is what he said:
Seals tests are part of the testing requirements for many specifications and claims. Specifically ASTM test D7216 is required for ILSAC and API performance claims. Mobil 1 motor oils are tested for compatibility with many types of seal materials including silicone seals. As lubricant developers, we are not always privileged to know the specific elastomers in each engine for each manufacturer. We rely on the auto manufacturers to ensure that all the relevant seal materials are required in the industry required tests or their own proprietary tests. Both regular and high mileage oils are tested in the industry or proprietary seal tests required for the claims that are listed on the PDS of the product. There should be no issues with using a high mileage product in a newer vehicle as long as that product meets the viscosity and claims required by the manufacturer. Lastly, we always recommend that our customers consult their owner’s manual to ensure they are choosing the correct lubricant for their vehicle.