Can high mileage oils cause leaks?

[ziggy]

Are high mileage oils really worth it? Ive read and been told, their clsoe to a 40 weight, in terms of 30 weight oil. However, they also say the stuff these oils use, to rejuvinate the oil seals, causes them to swell up, then the seals can shrink back, causeing a worse leak... ay truth to that?

 

[Merkava_4]

It's not so much their ability to swell seals as their ability to restore pliability to the seals; that is their main virtue. They also run a little thicker to fill in the gaps of a worn engine.

 

[ziggy]

SO would they be okay to use, without harming the seals?

 

[SFCP]

Along with ziggy, I REALLY would like to know if my van would perform better on a conventional blend vs a HM blend like Maxlife, due to it being thinner. ???

 

[MarkC]

Well, there's a good way to find out, and there's no sense drowning in 2 inches of water, so go for it.
Or not.
I used some Chevron High Mileage on my 10 year old Cherokee a while back, nothing weird happened. I wne tback to regular 10W30 and the used oil analysis was better than the one I did with the High Mileage. But that may be due to changing the plugs and wires. And air filter.

 

[01rangerxl]

I highly doubt you will run into leaks by using a High Mileage oil. I have put everything in my truck from 5W20 synthetic blend, to 5W30 high mileage, to 5W30 conventional, to 5W30 full synthetic with no leaks to speak of (85,500 miles). To be honest, the car probably doesn't care as much about the oil as you do. It seems to be that way with my truck.

 

[Merkava_4]

Quote:

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SO would they be okay to use, without harming the seals?

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High Mileage oils can only help your seals; not adversely affect them.

 

[Merkava_4]

Quote:

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Along with ziggy, I REALLY would like to know if my van would perform better on a conventional blend vs a High Mileage blend like Maxlife, due to it being thinner. ???

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I can only answer your question from a mechanical perspective: as an engine wears, the clearance between parts increase to the scale of thousandths per inch; so an High Mileage oil will be minutely thicker to fill in the increased clearances.

As piston rings wear, their spring tension becomes less. High Mileage oils that are slightly thicker, will help make up for the loss in ring tension by helping to create a better seal between the piston rings and the cylinder walls; that can help restore lost compression to a certain extent.