What makes High Mileage Oil... High mileage oil?

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Jul 4, 2002
Alright, the question is the subject: What makes "High Mileage" oil... High mileage oil? Such as Valvoline Maxlife and Quaker State's similar product? What do these oils really contain that make them different - or do they contain nothing that makes them different?
In reality, it's a lot of marketing, and not much change to the oil. They used to contain a lot more additives, like Maxlife did at first, but now it's only real big difference compared to their other oils is that it uses about a 10% ester mix for it's base oil, supposedly to help slow any leaks. Also, these high mileage oils often end up being on the thicker end of their respective viscosities. Other than that, they aren't much different.
I don't know for sure they really do have these seal conditioning esters as mentioned. IMO, from what I have seen between penz and valv high mileage oils, neither seem to clean very well. the detergents are lower, and I'd say for good reason. IMO, if you were to put esters in the oil, it would tend to clean things(according to some here) and if you clean an old valve stem seal for example, that has been crudded up, it would create a smoker letting oil pass by the harden seal. This is why I noticed that those oils didn't clean as well as the full synth's that is known to have esters in them. Also it appears that from some analysis, the high milage oils have a lower level of detergents. By doing this, it would not clean but also allow the existing crude to maintain the current seal properties using such. Now based on what I have seen in sludged engines, There was several mechanics trying to head off these sludge puppies as when they saw one looking like it was getting sludge, they'd put in half a qt of trans fluid which dramaticly increases the detergent levels. This would in fact clean a sludged engine, BUT, in doing so, within a 2 wk period, the car came back smoking, where the detergents had actually cleaned away the crud and left the harden seal. Look at those pics where I left the crudded up valve stem seals in each oil for 2wks and you'll notice, synth's, cleaned pretty good where as both high mileage oils did very little. Cleaning and Seal conditioning
I wonder if so many detergents are actually necessary in a modern engine oil for most cars? Also on the thicker note, I did notice in your oil report Patman that it was well over 11.xx cSt (don't remember quite what) which is kind of like a 10W-35 [Smile] Either way I'm sending mine off to be analysed as well, I'm curious why my engine seems to respond well to this Maxlife wheras it didn't do so well on the Mobil-1 (which did seem thinner). Thanks for your replies guys.
The more I think about it the more I tend to believe that cleaning these seals continuously isn't necessarily what should be done. I mean most seals should do their job and seal the engine, not get continuously cleaned and deteriorated. It looks like Amsoil and Mobil1 really tore into those seals on http://www.bobistheoilguy.com/sealconditioning/sealcondtioning.htm - and that would explain why many people get "leaks" from their cars when they switch to one of these oils after years of running xxx brand oil.
Originally posted by Dominic: It looks like Amsoil and Mobil1 really tore into those seals on
I think Bob's information shows that some oils tear into the deteriorated portion of the seal. This has the net effect of "tearing into" the whole seal. The question is do any of these oils preserve a sound seal any better?? Looks like a new definition of "seal conditioning".
Who on this forum has leaks on a 100K engine? I've got a 110k Windstar with no leaks and have been using Mobil 1 every other oil change. Changing at 3-5K intervals. Generally 3k when on Dino. Maybe the "cleaning" action has been good for my engine. I don't think M1 really cleaned so much as suspended the dirt and didn't allow it to be deposited on the engine. I don't think Exxon-Mobil wants M1 to act like Auto-Rx and clog up the filter in 500 miles as it "cleans". They must use different esters. Maybe the slight cleaning action has kept the crud off my seals enough to to keep oil in contact with them. [I dont know] My engine was cleaned with Auto-Rx at 103K and I really noticed a difference in power. I kept it in for 1,000 miles (meant to change at 700-800) and the oil was still clear. Don't think I had much sludge. I wouldn't want to run Auto-Rx continuously but I think an oil with esters/PAO in it will leave you engine/seals cleaner. I don't think M1 will do much cleaning unless you use it continuously for several drain and re-fills. I suspect it won't clean thru the really hardened stuff in the engine.
Actually JJ, I think just the opposite. The cleaning action that most synth's have are normally exceptional and I can understand completly why auto rx went with esters due to this. The problem I noticed is that if someone with any amount of miles on an engine, haveing used a conventional ok motor oil that doesn't have this type of cleaning action, that has incurred some buildup on the seals, goes to a synth and that starts to clean the seals and such. In many cases, I have seen and heard many state that after I switched to a synth my engine developed all sorts of leaks. I can see why. Because if you have slightly harden seals, and a full synth comes along and cleans off the crud that is on there and currently is helping seal the worn seal, then it can very easily create a leak. This is not to say the synth is bad for the seals. Just that this is would be one reason not to just switch to a full synth in this kind of case without doing a purge with 131 neutra or auto rx as both will do the cleaning and condition the seals back to where they can handle the synth oil. IMO, a basic synth oil doesn't actually condition the seals, but just like you stated, if it can keep them clean, and keep oil on them with no crud build up, then the seals would / should have no problems lasting.
Bob, you mentioned people putting trans oil in the engine to add detergency. I haven't seen the detergent levels of ATF, but it is hard to believe they are higher than a good diesel oil. Hopefully you aren't saying manual trans oil, as it is acidic and would cause it's own sludge when mixed with engine oil. From my reading here I would probably try auto RX or something if I had a sludged engine. Just don't have any to try it on. Could that be from not switching oils with every change? I don't know that we see enough from the little sampling we see here as to the effects of different oils on seals. I am looking at the 95 Villager I've borrowed for these three weeks. Has 218,000 miles on it and I don't see any drops on the driveway. The engine has seen nothing but Mobil 1 at 5,000 mile intervals.
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