Questions on proper chain maintenance
 

When I bought my new bike the chain appeared to have a heavy coating of thick grey grease on it. However the spray on chain lubes are more of an oil then the original grease. I was curious if the thinner viscosity oils are just as good (or perhaps better) then the original grease?

As far as cleaning the chain I have a chain brush but is that considered adequate cleaning of the chain. Should I try and remove all the original grease and just use chain oil? I know some people remove the chain and soak it in gasoline. At $4.50 a gallon I don't know if I want to waste gas cleaning my chain. I'd like to occasionally do a thorough cleaning of the chain but would like to know what's the best method to do so.

One last question on chain lifespan. What type of wear should I look for as I clean and inspect the chain indicating when the chain should be replaced? Or is it based on a mileage marker?

That grey "grease" is a wax based chain lube. O-ring chains are somewhat sealed, but if you use something that might attack the rubber of the o-rings, or get past them and wash out the real grease inside, it'll shorten the chain's life. I just brush most of the grunge off and re-spray mine with a wax type lube for the exterior lubrication.

I don't think that you want to soak the chain in anything. Assuming you have an O-ring chain, the o-rings function is to hold in the oil/wax/lubricant. By soaking the chain in kerosene/gasoline, you are breaking down everything that the O-rings are holding in.

A grunge brush has been suggested to clean the chain.

I use a controversial method, my chains last for years. Do it this way or not, but it works for me.
Soak in Kerosene (Camping fuel). Kerosene will not break down the rubber seals like gas will. Brush excess off with a wire brush. Re-install and spray it down with WD40. Done.

I like the dry lube since I am a clean freak. I think the heavy grease will keep chain noise down. As far as wear? I am not sure. The heavy grease will get full of grit so to me that is a downfall. I spray my chain a lot which keeps the grit off the chain and a nice lube left behind.

On my bicycles I never remove the heavy grease they come with from the factory (to prevent rusting). However, it does not take long with the spray lube for it to be all gone anyway.

The exact method to measure chain wear is in the manual. You have to measure the chain. You are looking for chain stretch that will make it not mesh on the teeth well. That will lead to hooked tooth sprockets. If you keep up with chain maintenance the sprockets will last a good amount of time.

Again on my bicycles I replace chains fairly often and end up getting years out of my cogs.

Agree^ I tend to go cheap and put the bike on rear stand, use a parts brush (stiff nylon bristle) and use kerosene with a drain pan underneath. Maybe not scientific, but gets the chain clean. Use a light lube of choice. Better to have a light lube you need to replace, than a heavy "grease-type" goo that will hold dirt and grit. Lube "fling" is not all bad; it gets rid of the gunk instead of holding it in the chain pathway.
Lifespan? Depends a bit on how twitchy your right wrist is; how much yank you put on the driveline. I'm pretty easy on the throttle, apparently. Watch your adjusters on the swingarm and teeth on your sprockets. When you approach the end of adjustment range or your teeth begin to either round-off or "hook," you need to assess the health of your moving parts.

I spray the chain off when I was the bike, then spray a penetrating oil on it to prevent rust, and lube the o rings. I like Inforce lubricant, and chains last me a long time.

I've soaked in kerosene when it comes off, and something like simple green and a brush when it's on the bike along with a gentle spray from the garden hose. Run around the block. Spray a little WD40, run around the block again, then finish it off with whatever chain lube I have available. Been using Silkolene or some other chain lube in a green can. Keep it clean. DO NOT pressure wash it and spray water under the o-rings. WD40 is not considered a good chain lube, but I've read reports of guys using it for many a mile.

Chains have a definite life span. Oring Xring blah blah blah all of them get old and the lube inside the OXrings expires and then the chain stretches wearing out the sprockets. Then its time to replace it all at once.

After washing spray on WD40 then ride the thing up and down the street then use chain wax or whatever to prevent dirt build up

Nope, it's mostly solvents and ~15% mineral oil. I wouldn't use it for this...