Good questions. I learned about the lubing thing with trackbar bushings which, admittedly, are more prone to wearing out than just about any other bushing on a Bronco. The spring eye bushings are not subject to as much movement, but in the early days they were real squeakers, so we started dabbling in different lubes to reduce the noise factor.
The poly bushing companies usually have a real thick silicone based lube that is resistant to washing out and fully compatible with the poly. And although I've installed spring bushings without any lube before, I highly recommend lubing at least the inner bores of both the bushings and the sleeves. Does double-duty. Keeps moisture out (reducing rust issues on the bolt and sleeve) and helps them spin around each other (reducing wear).
If it keeps them quiet too, that's a big bonus. Personally though, I've never had any poly squeak on me, lubed or not, so I'm not talking from personal experience on that. Just heard all the complaints from others.
I used to go through trackbar bushings pretty quickly. Even those I'd lubed lightly with the silicone lube. So finally I started (purely by happenstance) using that nasty "Anti-Sieze" stuff since that's all I had laying around one day. Hmm, funny, but that set of bushings lasted 10 times as long as the previous 3 sets. Well, more than 10 times actually. I never replaced them again and they were still working fine the last time I drove my Bronco. Coincidence? Maybe, but...
I don't think I've lubed the C-bushings before, but I've heard of a lot of people doing it and it makes sense. I don't think you're likely to get any squeaking out of one, but the lube can probably help keep things aligned and going smoothly during the initial installation. I'm sure others will have better opinions on that, but it makes sense to me, from an installation standpoint anyway.
As for "graphite impregnated", funny you should bring that up. I've been meaning to find out if any of the other companies have started using graphite, or some other lubricating characteristic, in their poly stuff. Unless things have changed in the last couple of years though, the only manufacturer that I'm aware of that impregnates their bushings with graphite (the black ones only) is Energy Suspension. So if yours are black Energy Suspension brand bushings, you've got graphite.
I don't want to spread mis-information here, as things could certainly have changed over the last couple of years, but up until a few years ago at least, Energy was the only one. Most Bronco vendors have used ES products at one time or another, either as-is, or as private labeled products, so it's very likely still common stuff. If yours are another brand, or un-marked, double-check with your supplier.
I used to work for Prothane, and at the time, they did not add graphite to their products. They had excellent "lubricity" when new (in other words, they were pretty slippery), but we also sold silicone lube as well, for just the reasons I described previously. For a few years you could even special order Rancho bushings with graphite. They were sort of a grey/red color and made by Energy exclusively for Rancho. They were about twice the price of regular Rancho Red bushings though, so we didn't sell very many at the time.
That's a long way of saying basically this:
If you've got graphite, great, you don't absolutely have to add lube.
If you don't have graphite, absolutely lube them.
If you do have graphite and still aren't sure just which way you want to go... When in doubt, lube it. If nothing else, it keeps the rust away longer.
Paul
