It's to clean a chain, not lube it, i use wd40 wherever i need to get rid of grease, wheel rims, swingarm etc. If the O ring is cacked the grease is coming out anyway, that's the point, if your O rings are good, it's fine, if they are nacked it doesn't matter either way. Still you are not soaking the whole chain in a bucket of it, just spray on, brush off.