Best exterior rubber protector and renewer?

The safe ones, like Meguiar's #40 Vinyl & Rubber Cleaner/Conditioner, are water-based and therefore not weatherproof. They'll still help restore rubber parts. However, you may not care for the shiny result.

You could use a silicone spray, but keep it off your paint.

You don't want to treat wiper blades. When the rubber oxidizes, it's time to replace them.

I have had excellent results with STP Son of a Gun and 303 Vinyl protectent. They work fine with rubber.

You might go to a camping/RV supply dealer (like Camping World) and look for a product called "Slide out Rubber Seal Conditioner" made by Camco. This is a foam that is intended for the rubber seals on the slide outs on motor homes and trailers, but is a good all-around rubber conditioner and protector. If you follow the directions, after thoroughly cleaning the rubber surface, I think you would be satisfied with the results. I have used it on several vehicles seals and it seems to work great. Maybe others on this site have more info on it.

Good luck,

TRCSr

Porsche used to recommend wiping down all door seals and other rubber with glycerine at least once a year. I remember doing this on my '75

911S years ago and being impressed with how new it made the rubber feel & look. German rubber quality was a big issue back then. Might still be. Now surely there's some jokes to follow THAT remark!

--Geary

Now that you mention about the glycerine, I do remember hearing about doing that many years ago. I think my father did that to his/my Austin Healey many back in the 70's. I have contacts with a few chemists and I will see if any of them have a comment on that.

TRCSr

I cannot help with a product name BUT I do know the stuff VW sell for the rubber bits and bobs for the Eos CC works very well - protects things and keep them supple

Many years ago a mechanic at a VW dealer where I bought my first RV (Westfalia van) told me that plain ole vinegar was good for rejuvenating rubber by replacing the rubber oils, but I don't think it would add any amount of protection.

TRCSr

I use vegetable oil (cooking oil) to clean polish residue from the rubber stuff, such as the windscreen surround and window seals, after a good clean-up. I have no idea whether this may rejuvenate the seals, but it's gotta be worth a try. It will also remove polish residue from black plastic bumpers and trim and clean them up very nicely.

Vinegar? Surely you jest!? Vinegar is a mild acid iirc. It sure wouldn't replace any oils in the rubber. Might dry them out but ...... Now my wife might come up with something like that if someone had once told her 'vegetable oil will do the trick, ya, the same stuff you use in vinegar and oil salad dressing' . Could that be it, a mix up?

Chris

99BBB

No, I do not jest; I don't remember many things from the 60's, but I distinctly remember the VW mechanic telling me that. Maybe he had some sinister motive - like ruining all of my rubber parts so I would need to replace them. Yes, vinegar is an acid - acetic acid I believe, but I am not sure that it would really damage the rubber, but I also don't really think it would do it any good. The Camco Seal Conditioner that I mentioned in my first reply is still my best suggestion. I am not a chemist so I am not sure what vegetable oil or acetic acid would do to rubber; that is why I tend to buy products made and sold by professionals, people who supposedly know what they are doing.

TRCSr

Well, I tend to like a good home remedy sort of thing when it does the job well. Maybe the vinegar simply removes all the oxidized rubber and gets down to the better rubber just below!? It's possible I guess.

cd

99BBB

The door seals etc were probably once made of natural rubber. Now they're synthetic rubber - EPDM. Weather resistance is much better than natural rubber. (They still use natural rubber in tyres, along with styrene butadiene (SBR and BR) synthetic rubber, and after a few years or less the sidewall surface gets crazed and chalky and loses elasticity). Silicone oil makes it look nicer, they even use in the tyre factories for that reason. They wouldn't (or shouldn't) use "plasticiser" oils in EPDM mouldings, which would cause shrinkage / loss of elasticity when they finally evaporate or leach out, so something like silicone oil should be safe, though it might not be safe on some flexible plasticised materials, like plasticised PVC in parts not designed for exterior exposure. The same property that makes rubber molecules rubbery (double bonds) also makes rubber vulnerable to UV light. Silicone rubber was going to be the answer to that, but wasn't as good as as hoped for in practice, and usually has very poor tear resistance. The window seals on my 20+ year old truck, which is never garaged are still okay. Judging by the very black residue on the surface which cleans off on a rag, the loading of carbon black in the rubber is very high, and that carbon black is preventing UV from penetrating and damaging it further. I just use silicone oil from a spray can to clean/condition it. I don't think any "UV absorber" in some protectorant is going to make any significant difference, as you're not going to be able to get enough on and keep it there for long enough, and they are usually sacrificial and break down fast. Perhaps some anti-oxidants could help, so perhaps some proprietary products do have some small advantage. I heard that ATF is good for restoring the look of under-bonnet rubber components, but I'm not game to try it myself. I wouldn't use any oils or solvents or waxes on weather seals. EPDM is relatively very weather resistant, oxidation and ozone resistant, but not resistant to hydrocarbons. For that reason, (and to save getting it all over the paintwork) if using silicone spray, spray it on a rag and wipe it on, as if sprayed directly then it will still contain HC propellants. I know that some formulators of solvent-based "tyre shine" cut silicone oil in hydrocarbon solvent, so I'd really avoid that as well. Water based emulsions are probably okay, but IMO a bit pointless/expensive.

Well shit, all of us 'know-a-little's give our 2 cents (probably not worth that) and then the lurking 'rubber engineer' gives us a serious lesson in rubber! ;-) It is amazing, the amount of knowledge different people have on different things, eh? Hey 'Me' thanks for the lesson! And what in the world is your name? We can't go around calling you me, that would start to sound like the old comedy routine!

Chris

99BBB

I'm just "me", and not a rubber chemist. An afterthought to below, the suggestion I heard to use ATF (or power steering fluid) to freshen up under-bonnet rubber isn't a good one. While that stuff will be formulated to protect/not attack rubber components in power steering units and auto trans, I'd expect that rubber is nitrile etc. But coolant hoses are likely to be EPDM, and although it's got good heat/water/glycol resistance, it doesn't have good resistance to oils - so IMO it's a bad idea to wipe it down with ATF etc.

When I said "once made of natural rubber", I meant very old vintage cars. EPDM will have been used for many decades. I think it was invented in the 1950s, but I can remember cars from the 60s with window seals that hardened, cracked and crazed quite quickly, so perhaps another less durable synthetic rubber was still being used long after EPDM was invented. Also, how long it lasts is going to depend on the properties of the EPDM and how it is compounded with other materials, as well as exposure conditions. I'm confident that the exterior rubber in any Miata will be EPDM.