Ok, I'm putting parts of my engine back together and I'm using some old rubber parts that are in good shape- but I'd like to lubricate and protect them.

For example- I have the rubber O-ring right under the oil filler neck. Don't have time to run to Pep-Boys again today so I gotta use something I've got. The choices are:

*Engine oil
*CV joint grease
*WD 40
*White Lithium Grease from spray can
*3in1 Houshold Oil

Or I probably have lots of other stuff that would apply. I just don't know what dries out rubber (alcohol? acetone?) that I should avoid, and what I should use, if anything. Also, I have wiring boots on the outside- what to use on them?

You'll probably think I'm joking but try spit. Yes, spit... surprising how nice rubber is after a good spit bath. Of the ones you mentioned- lithium grease.

Ok but the only thing that gave me doubts about the White Lithium Grease in a spray can is that it says it's for metal to metal, and the ingredients are mineral oil, hexane, propane, isobutane... which I thought would be similar to acetone and dry rubber out.

Be patient, get a new engine gasket kit, and go to your local pool supply store when you get a chance. Yes, you heard that correctly, pool supply store. Get some of their marine silicon grease. Not the kind that hardens like for glass, but the kind that doesn't dry. Apply liberally to your o-rings for the pushrods and stuff. For things like the oil cooler seals you'll want some non-hardening sealant like what loctite offers.

Be patient, do it right.

OK, perhaps 3&1? Engine oil, WD40 & CV grease are all petrolium based, which breaks up rubber over time. I don't know what's in 3&1. I like the sound of the marine sealant... sounds like a type of plumbers grease, which is also OK for rubber.

I'm not doing a complete tear down at this point... since the engine was running well when I pulled it. All I've done is removed engine tin, vacuum lines, fuel lines, and all the external stuff. Plan is to clean it on the outside and put it back in the car. Engine rebuild with the full gasket kit will probably take place in about a year. So I'm just dealing with minor rubber parts right now.

take place in a year?

as long as its not cracked now i wouldnt think much about it.

slap on some engine oil and put it in. that piece sees no sunlight or anything and LA isnt that hot.

-jim

Careful there. No o-rings for automotive applications are made of natural rubber, they're all of materials intended to be used around oil. Gaskets are used where there's no movement between two pieces, and o-rings are used when there's movement. That's why it's so important to make sure the pushrod tube receivers in the head are smooth, for example, so those o-rings can move in and out without being scored by a rough surface. And since they're designed to move they NEED lubrication to work and seal. If you install an o-ring dry or with any kind of sealant you're turning it into a gasket and preventing it from working the way it was designed. Sometimes that's fine, like that oil filler neck where that "o-ring" is really functioning like a gasket, but the general rule is to lube them on installation with whatever liquid they're going to be around, and that's generally oil.

I'm a fan of silicone grease as it is easier on the rubber because it is not petroleum based. I agree some o-rings are designed for oil contact but I still coat with silicone grease. Pool stores have it readily available.

The general rule is to use the lubricant that is being sealed out. This is most important in shaft seals. They should never be installed dry. EX: In a tranny, use the gear oil.

The pool supply stores have Teflon grease, too. Great stuff. It's waterproof and sticky, works super on elastomer and poly suspension bushings.

Silicone grease is the preferred lube for rubber O rings. I wouldn't ever use silicone sealant on any O ring. The purpose of most O rings is to allow some movement (as in thermal expansion), which would be circumvented if you sealed it in place. I know there are some exceptions to this, but if you are asking for free advice this is mine.

I always use the spray silicone on rubber seals, several original seals on the '79 bug, and it spent a lot of time in the sun. I like the silicone grease you use on spark plug boots for something thicker