Quick facts:
Type: Penetrating grease
Application: Aerosol
Wear rate: 64.87 nm/km/link in harsh conditions
Corrosion resistance
Recommended

Zep 2000 is self-described as a "Heavy-Duty, Clear, Penetrating Grease." I found it by chance in a small gun shop. It's one of the types that has a fairly sticky grease dissolved in a light solvent. The solvent carries the grease into small areas, then evaporates. This is similar to some motorcycle lubricants, but I beleive its intended use is various commercial and industrial applications, such as chains and conveyor belts.

I started using it because I didn't have anything else available at the time. However, I've been pleasantly suprised by how well it works. I recently replaced cassette and chain. The chain is a SRAM PC-48. Since I've ridden about 225 miles over about 1-2 months in harsh conditions, and the chain has only elongated about 23 µm per link--about 64.87 nm/km wear rate so far. I've never had such a low rate of elongation, although I can't be sure this is due only to the lubricant. At this rate, the chain would last for more than 5000 miles.

The chain doesn't have a particularly nasty rub-off as is typical with some wet lubricants. Despite having been ridden and left in the rain a few times, the chain so far shows no sign of rust. After degreasing and brush cleaning, there is no appreciable buildup, as sometimes happens with greases on chains.

This is on a mountain bike, and my riding pattern consists of road riding, short distance commuting, and off road riding. The chain is exposed to rain, road water, and some wet dirt/mud.

A final observation is that this lubricant gives a very smooth feel to the drivechain through the pedals that is typical of using grease instead of a light or dry lubricant. I'm not sure this affects power efficiency.

Anyway, if you need to use a heavier lubricant on your chain because you're going to be leaving your bike on a bikerack, riding in the rain, or going off road, I'd definitely recommend this stuff. I'd put it in the same catagory as motorcycle lubricants or Phil Woods Tenacious Oil. The stuff is also cheap and easy to apply in a convenient aerosol. However, it may be somewhat difficult to find.