Originally Posted by Mad_Hatter
Originally Posted by Dave9
Don't. Seal swellers (dubiously called conditioners) are meant to increase the size of the seal to make up for wear, while necessarily decreasing its density so it wears that much faster. Using one then switching back to non-HM oil can make the leak worse than if you'd never used it.
If this was beneficial for new engines, it wouldn't be called high mileage oil, but consider that engines now last a long longer than they used to. 75K miles decades ago is more like double that today.
I'd never use it
at any engine mileageunless I had unacceptable oil loss and as a last ditch effort to keep it running a bit longer while I contemplated what to do next (unless it was a rarely used vehicle).
That's hogwash..if anything you said was true, oil mfgs would have to slap a big
RED warning sign on HiMi bottles to CYA themselves.
Why would they do that? You think they'd be liable for your seals wearing and then needing their oil more than ever? That's what they want, and no customer is going to be able to prove that their sample size of one, wasn't just normal engine wear that wouldn't have otherwise happened.
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Anecdotally, I've got nearly 170k miles on my engine and from day one I've switched back and forth from HiMi to vanilla. In fact I've got RGT in the sump right now and prior to that I ran Havoline HiMi syn blend and prior to that Kendall GT1 and after this run of RGT I plan on using M1 HiMi. I guess I should expect my engine seals to grenade any day now according to you!
..oh, and at 170k miles of going back and forth, I don't burn a lick of oil that I can discern between oil changes. 5.5 goes in.. and 5k miles later apprx 5.5 comes out.
You're correct, that it's anecdotal. The one constant is that seal swellers do nothing good for seals that don't need swollen to make a seal. Now about your sample size, maybe you start getting leaks at 200K mi but wouldn't have until 250K mi otherwise. It's no great feat to reach 170K with the last few generations of engines.