Question for Jestal

Jestal - do the "High Mileage" oils like the one Quaker State touts do any appreciable good for "older" cars? What is the difference in these oils as compared with "regular" oil? Thanks!

Jim

Even though I'm not jestal, I'll take a crack (no pun intended) at explaining how they work. It is my understanding that these high mileage oils have additives that help soften older engine seals and help them swell a certain fraction and help keep oil from escaping through vapor, that either escapes to the atmosphere or finds the combustion chamber and gets burned. Certain engine seals, can over time, harden to a certain degree and may not be able to maintain the tolerance they once may have had. These type engine oils can buy time for older engines but ultimately you can see where this is heading. The oil companies tout 75,000 miles as there magic number but I think engine age, oil change maintenance and sevice life would have a much more profound impact on the engine seals they claim to be helping. Many engines live long an happy lives without these special oils, but if your engine has had a hard life, and the seals have hardened over time, they may actually do some good.

The oils advertised for older engines or high mileage engines probably contain some "seal swell" agents to reduce the tendency of the engine to leak. Sounds like a good idea but more effective in theory than practice I would say from what I have seen.

If you look at the can of oil and see the ILSAC starburst symbol on the label with the "for gasoline engines" terminology in it then you know that the oil meets the GF3 or GF4 (these days) standards that the oil industry and the US car makers agree on. To be a GF4 oil means that the oil meets the minimum performance requirements (such as SL) and that it contains friction modifiers for fuel economy improvement. The whole idea of the GF3/4 standards was to provide an oil on the shelf that "most" people will buy that meets the proper performance standards to protect the engine...i.e...SL... AND contains the fuel economy enhancing additives. This is important to the auto companies because, if they can prove that the customer is likely to use that oil, then they can certify the vehicle using that oil and reap the benefits of the fuel economy enhancing friction modifiers for CAFE purposes. In addition, GF4 oils contain relatively standard levels of the antiwear additive ZDP. The "P" in ZDP is for phosphorus and phosphorus poisons catalytic converters as the engine burns oil. The desire for the fleet on the road is to keep enough ZDP in the oil to protect the engines against wear but to also minimize it to minimize catalyst poisoning to keep the emission systems on the engines operating for as long as possible.

So, the second part of the answer is to look at the can of oil you are wondering about and look for the starburst symbol. If the oil for aged engines or the oil for extended service contains the starburst then it is little different from the other oils on the shelf with the starburst, basically. It will contain similar anti-wear additive package concentrations and it will contain similar friction modifiers.

If, however, the oil is NOT rated with the starburst it is NOT a GF4 oil and it will likely NOT contain any friction modifiers and it will likely WILL contain a higher concentration of anti-wear additives and additional antiwear additives. That is why oils like the Delvac/Delo/Rotella are marketed as "diesel oils". They meet the diesel specs, yes, but, more importantly for this conversation, is that they do NOT meet the GF4 standards because they have no friction modifiers and they contain more antiwear protection. Perfectly fine for gasoline engines, too, but if everyone started using them it would wreck the certification process the auto companies have put into place with the EPA...

Some of the oils for older engines and especially oils like the Mobil Extended Service products are specifically NOT GF4 rated if you look. So the natural assumption would be that they contain no friction modifiers and have more antiwear protection in addition to the "seal swell" if applicable. The antiwear additive ZDP is sacrificial in nature...i.e..it gets used up over time doing its job...so when the ZDP reaches a low concentration the oil needs to be changed no matter what other factors are involved. Hi mileage oils intended for longer change intervals MUST (practically speaking...there is no rule or law about this) have more ZDP in them so as to not be depleted of ZDP with extended drain intervals.

So the answer to the first part of your question is that I feel the "for older engines" oil is primarily a marketing ploy. If the engine is older and relys on more protection from the lubricants then there is certainly an advantage to using the non-GF4 oils that contain additional antiwear protection. That oil might or might not be labeled as "for older engines" however.

Thanks to both. Jestal - I always enjoy reading your thorough posts! Thanks again. Jim

Thanks AL -- I always learn something reading your technical posts.