My '88 GT has 22,000 miles so clearly not "high mileage", but still 36 years old.

What do folks think about using high mileage motor oil? Is the seal conditioner in that oil's additive package really intended for the AGE of the soft internal seals, or the WEAR associated with high miles?

Thoughts??

quote Originally posted by FieroMark: My '88 GT has 22,000 miles so clearly not "high mileage", but still 36 years old. What do folks think about using high mileage motor oil? Is the seal conditioner in that oil's additive package really intended for the AGE of the soft internal seals, or the WEAR associated with high miles? Thoughts??

Back in the day (20 years ago), we used to add transmission fluid to our normal motor oil in order to get the seals to "swell." This would help seal them supposedly. I don't know if this is still true. But there's a lot of stuff that's been taken out of oil that should have been in there. At 22k miles, the motor likely still has the hatch marks on the cyl wall. I'd just go with Synthetic and maybe (for the sake of the lifters), use some additive like ZMAX or something.

Flat-Tappet Cams and the 'Right' Engine Oil MATTERS!

Read This Thread - "Engine Oils Have Changed Over Time from the Fiero Era"
https://www.fiero.nl/forum/Forum2/HTML/147614.html

The API SF rating on the V6 was critical for the flat-tappet lifters/cam engine, but the SF specification is now obsolete.

As Synthetic Oil - There are two sides of the argument about the danger of running synthetic oil in a flat-tappet cam engine.

To me, I still use conventional oil in all of my classics....

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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

Can go by age not miles for Fiero...

Valvoline was the first "High Mileage" oil and could work if Only the "rubber" seals like on the crank nose was hard.
If have a leak over a drip or 3 a day... could work or not depend what is leaking etc.

All others came latter when Valvoline got good reviews from most if not all trade & auto rags.

⚠️ could add ZDDP etc but many products add way too much not only make the engine wear out, can Poison the Cat. Is Why current API reduce some chemicals in engine oil.
Other additives actually reduce cleaner other chemicals in engine oils because many have no cleaners etc so dilute the main oil by the amount of the additive "bottle."
More Zinc = More Wear? The REAL Truth About ZDDP Additives https://www.youtube.com/watch?v=erxjPicpYyw
If You LOVE One Of These Additives, DON'T Watch This Video! https://www.youtube.com/watch?v=CAGT5inQScE

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Yep. I've watched a lot of video from Lake Speed Jr. Dude is a lube scientist. No bull....

I, too, watched Lake Speed's videos and clear evidence that adding ANYTHING to your oil puts you in the category of experimental chemist.

I was just wondering if hi-mileage oil acts in a way such that seals actually wear quicker after some period of time. You know, beneficial for a period then actually becomes harmful. My 2.8 has zero leaks at this time, and I'm just trying to keep it that way.