I would like to soften and condition a pair of original tan vinyl seats. At 50 years old, I consider them somewhat fragile.

A google search gives me mostly lists of amazon products with affiliate links... but I've noticed a few references of using mineral oil.

Of course, I don't want to use anything that will weaken the vinyl.

Any trade secrets out there?

Maybe Murphy's Oil Soap. It works on old leather.

There’s no way to soften or condition, vinyl or synthetic products.

Over the years I've had success bringing old rubber seals and the like (even -display only!- tires) back to service with a thin glycerin solution. Soaked and bagged for sometimes weeks to return pliability. But vinyl is different, especially if sun exposed...when it gets brittle there's not much you can do. German vinyl is especially rugged though, both surface and dyes contain organic esters that mineral spirits or products like Pre-Kleano can rescue, if still somewhat pliable by reintroducing moisture.

FWIW, nearly all of the vinyl/rubber conditioners available contain similar formulations, or you can make up your own. Please post results, and good luck!

Vinyl is blended with a plasticizer. It evaporates or oxidizes over time. It is the film you get on the inside of the windshield. I don't know of any way to put it pack in. Leather is a different story as it absorbs oils and softens up.

Everything out gasses. Leather is an animal's armor. It out gasses & then in gasses. I suppose our skin does the same thing. OTOH, both leather & vinyl clean up rather nicely. Cheap leather doesn't last. My 914 seats still look & feel really great. Minimal UV light exposure.

Can you tell that I'm still trying to sell this car?

Anything that penetrates the vinyl will dry out and make it more brittle. You can dye it, but it's a temporary solution.

all the plastic experts have already spoken and all are correct.
most notably @Mikey914

about all you can do is keep it away from UV.
or minimise exposure.
and even with that its going to give up the ghost at some point.
its slowly loses the plasticizers . and they can't be replaced or replenished.

new vinyl or plastic is the only redemption.

FWIW, a bunch of years ago I jumped into the "restoration" of a 1985 Alfa Spider that had been swallowed up by the surge waters of hurricane Sandy. Will probably not do another flood car again, but, the soft top was (is) vinyl. 3 in 1 oil has softened it up and is still working 10 years later. Yes, it will not fly for a concours project, but a street beater it works well.

There was seaweed in the rear view mirror attached to the header bar, she was submerged

The one thing I will refuse to do is get involved with a saltwater flood car.
every single printed circuit board will die over time.
A flooded Italian car is the stuff of nightmares...

All plastics die as well.

Chrysler is the worst IMO. It's like they left out one ingredient and the plastic get brittle twice as fast as everything else.

I hate a dash pull on a 25-year-old Chrysler. If it's not cracked when you take it apart it will be when you put it back together.

My 914 (47 years old) has been dormant and garaged for 30+ years.
It's been hibernating in a dark cave for that time, out of the sun.
The rubber and plastic are in un-believable condition. The original stuff was tough, much tougher than what is available new today.

I'm still being very careful with the original seats. The passenger side already has the cracks in the corners. I'm sure it will fail if I stress it.
I've got replacements for them...

I have a 912e that the seats were in perfect condition. After the wife and I drove it rpthe passenger seat started cracking. Even though we treated it with Aerospace 303 for UV it had already got had enough that after a short usage it cracked.
Needless to say I’m working on reproducing the pattern now.

Way to get busy. Keep up the good work/service

How does the 912 run?

I remember a room mate years ago who put Armor All all over the seats in an old Audi. What a mess!!! With all the out gassing I don't think he ever got his windows clean.

You beat me to the punch on this post as I was going to ask the exact same thing this morning. I have a new dash top installed and want to keep it from cracking...but how? My hopes of something replenishing the vinyl are unfounded I now realize but fighting the UV damage seems to be the only option I have. I have mineral oil but I guess that will do nothing. 303 Aerospace Protectant sounds like the best option...any feedback from anyone? Also, my '73 steering wheel is soft and I am not sure what it is made of? It has fake stitching on the inside and could very easily start to crumble on the outside portion if I am not careful how I handle it. What is it made of? And the best treatment for it? Decisions decisions but how do you turn the clock back on a fifty year old car? Thank you,
gg

3 in 1 oil worked for me

Foam rim on the wheel. It degrades like everything else.

Ford Australa must have sold them the secret formula developed in the late 70s for the plastics in an XD Falcon.

I was young and xwys (60 y/o) I ditched the Bosch injection and spark control and am running twin Weber 40 Dcoe with a points ignition. The surge must have been from the Hudson river (fresh) because there was/is no rusting.

My days of flood car restoration are over, one and done