On motorcycle forums, the overall consensus has always been that the best way to lube the chain is to apply the lube right after a ride, while the chain is still warm. Wouldn’t it be more effective to, rather, warm the can of lube in, say, a pan of hot water and apply it to a cold chain? Wouldn’t the parts of the chain be tighter on a hot chain, thus impairing the penetration of the lube? By warming the lube itself, it would be thinner, thus aiding penetration. Or would a warm chain somehow “wick” the lube in?
It’s been decades since I had a bike with a chain but when the chain heats the metal expands. Not sure why you say it gets tighter. I would think it would allow the lube more easily into the cracks and crevices.
I was thinking of the tolerances getting tighter* because* of the expansion, but I was probably overthinking it. No physicist me 
I think hot makes more sense. The connecting pins should be designed so that they don’t expand as much as the links to reduce wear, so when hot there should be more room for lubricant to get in.
All in all, modern chains don’t need the kind of lubrication required in ye olde days. The life of chains is much longer and they don’t stretch nearly as much.
If you have two metal parts (same type of metal for both parts) with a clearance between them, then when the parts grow due to thermal expansion, the clearance will grow, too.
Not by much, though; it’s all proportional. If your parts grow by 0.1%, then your clearances grow by the same percentage. So a 0.003" clearance, when hot, becomes a 0.003003" clearance. I doubt this will make much difference in lube penetration.
The biggest difference is likely to be that warmth lowers the viscosity of the lubricant a great deal, enabling it to flow more easily into tight gaps.
Applying hot lube to a cold chain you’d either heat up the chain or cool down the lube.
I bet 99.99% of your chain oil is flung off the chain (centripetal force) within a few minutes of use, Whatever stays on is pretty small-but its enough to attract all kinds of dirt.
Not necessarily. I use chain lube that sprays on but becomes gel-like after a few minutes. It doesn’t fling off much, but of course still attracts dirt like sugar attracts ants.
Running an open chain for a long time:
Remove chain and clean well.
Heat pan of grease, wax, lube, Vaseline in my special ratios and add chain.
Let cool while pulling the chain from the ends to take out any slack and then pushing to get the slack out of the links the other way. Use needle nose pliers to avoid burning your hand.
Let cool to the point you remove chain & let totally cool.
Wipe any excess off & reinstall.
Provides a good long lasting lub that is majorly not sticky so collecting dirt & dust goes way down.
If you do not run your chain dirty, car washes everywhere, you can get over 10K miles out of a chain.
Not done much by today’s, throw away & buy new, riders …
YMMV
Most people overlube their chains, meaning too much lube each time they do it. It doesn’t take much, just do it before every ride. If you’re out on a long ride carry lube with you and put some one each time you stop off somewhere. The spray cans are designed to make you use too much.
I can’t understand why bikes don’t come with chain oilers. Are there any?
A warm chain will help the lube to stay less-viscous as it “flows” between the plates of the chain (also, slowly spin the chain/wheel to aid this). Lube sprayed on a cold chain would thicken more upon contact, and not flow as easily between the plates. Once applied, wait a few minutes, then wipe off all the excess w/ a rag. Anything that will come off on the rag would not have been assisting w/ lubrication anyway. May as well take it off with the rag before it slings all over your bike.
p.s. Yes, some bikes do come w/ oilers.
Just don’t do what a dumb-ass friend of mine did 35 years ago and lube your chain by wrapping an oily rag around your hand, putting the bike on the centre-stand, starting the engine and putting the bike in gear, then rubbing the rag over the moving chain. This went exactly as wrong as you would think (well, he lost only part of one finger). :smack:
There’s more heat in a warm link than the tiny drip of oil that’s going to reach that link - thus, a hot chain is more likely to result in heated oil; a cold chain will cool off the oil.
You want warm oil on a warm chain, it flows better as others said.
I recall taking a trip from western Canada to New Jersey and back many many years ago. When I took the chain off (to replace it) the bike mechanic demonstrated wear. he laid the chain on the ground straight, stated pushing, and had moved the one end 3 inches before the other end started moving. That’s a lot of slack. it was time for a new chain. I guess I shoulda oiled it better.
If you have dissimilar metals that expand at different rates, different temperatures will create different tolerances between them* (possibly tighter, possibly looser). Odds are the chains are mainly similar metals (assorted steels?). After all, they are designed to run at the warmer temp once in use for a while, why would that need to be tighter? I would just make the chain wear faster, squeeze out the oil, etc.
*I.e. if the inside bushing expanded faster than the surrounding cylinder. To much differential, it would seize up tight when heated.
I use a Scottoiler. Job done.