opinions on grease/oil & battery disconnecting

Yes - oil and grease are 'self-healing'. If the surface is scratched then the remaining oil or grease moves in to fill the gap and continue the protection. Paint cannot do that. On the other hand - paint is nice and clean and shiny and pretty. Oil and grease attract dirt and are messy and unpleasant. Naval aircraft are regularly sprayed with WD40 to prevent salt water corrosion.

Kev

A pot with some old engine oil and a paint brush are a great tool for treating such areas.

Grease will seal better than paint on rusty surfaces, and can also prevent rust on surfaces prone to corrosion.

Unless rusty surfaces are treated properly, paint does a very poor job of holding rust at bay. Surface rust is often the result of rusting from the other side of a panel that rust has made porous. Without treating both sides, any treatment is not going to stop further rusting, just slow it down a little.

Ordinary grease though, like that used in wheel bearings, tends to wash off, so doesn't give lasting protection. Water pump grease is better, but some years ago I discovered? a product called 'Protectol'. An industrial type protective grease that dries to a fairly hard waxy finish. I use it to coat the exposed threads and heads of any bolts, nuts etc, whenever I do any maintenance that needs their removal. I also use it to paint any underbody surfaces that are prone to rust. Even years after treatment, rusty screws and nuts that were refitted, remain free from further rusting, and are still easily undone.

Waxoyl does a similar job, but IMO is not very good at protecting underbody surfaces exposed to the elements, like wheel arches, chassis parts, nuts and bolts etc. Mike.

The message from "Mike G" contains these words:

Better suited to the insides of box-sections and sills.

============== Until about 30 years ago it was normal practice to spray the undersides of cars and other vehicles with a light oil to prevent corrosion. It worked pretty well on the whole but wasn't totally successful unless the inside of chassis rails were sprayed as well.

Cic.

The message from "Cicero" contains these words:

Until about 20 years ago most cars sprayed themselves with oil on the underside - my Fiat 127, Allegro and Astra certainly did.

What? Naval aircraft?? ;-)

Kev

Could be, I've never worked on one of those though :-P

I spray bare metal under the bonnet with WD40, taking care not to get it on the exhaust (it stinks!)

This has help prevent salt corrosion - esp. things like electrical contacts.

Started doing it after a colleague complained that his car had overheated and warped the cylinder head - cause was the fan did not come on in heavy traffic, because the lead which sensed the engine temperature had corroded and was just not working. Don't know why it wasn't fail safe, but there you are.

Plug and sockets that are not sealed particularly well, often show signs of corrosion on the terminals inside. To reduce the chance of them causing trouble, it's not a bad idea to pull them apart, and fill the socket with Vaseline or similar, then plug them together, and wipe off the grease that squeezes out. Even better than spraying them with WD40 or similar IMO. Mike.

If an engine has been steam cleaned by a used car dealer then it will attract rust like nobody's business. New cars are often wax sprayed under the bonnet. It gets a bit grimy looking and dealers often clean it all off. A spray with WD40 or similar every few months helps to protect things. Rusty bolts and corroded connections become a problem if neglected.

John

Raises an interesting point this. It is standard practice to smear vaseline on car battery connections to prevent the white fluffy corrosion deposits from building up. On replacing a battery on one occasion I smeared vaseline on the battery terminals prior to replacing the connector clamps. I found that the terminals became very hot in use. Thinking that the battery was faulty I returned to the battery depot and was advised by the auto-electrician there that you should never put vaseline on the battery posts *before* putting the clamps on. He stated that vaseline is not a good conductor of electricity and what I had done, in effect, was to put a layer of insulation between the posts and the clamps. After removing the clamps and cleaning the vaseline off, the battery was fine. If this advice is correct (and it seems make sense!) then filling an electrical connector with vaseline or grease would not be a sensible thing to do!

Kev

I appreciate the point you're making, but a push connector with a few pins is mechanically different to that of a battery connector. A battery connection relies on a large surface contact area to carry the high current demand that the starter makes. Any grease on this large surface will reduce it's efficiency, as even after tightening the clamp, grease will still remain trapped in the contact area. OTOH a pin connector only has a small area of contact, and although small, the contact pressure between the pins and mating sockets are comparitively high. Meaning as they are plugged together, any grease is actually scraped away from the actual contact points, leaving the surplus grease to waterproof the plug and socket unit itself. There is also the point that the current carried by such connectors is relatively low.

If you have a good MM you can prove it for yourself by joining 2 lengths of wire with a Lucar spade type connection. You'll find greased or ungreased the resistance remains the same. Mike.

I do have a MM - but I'll take your word for it!

Kev