Whether or not WD-40 will keep your chain's O-rings happy or ruin them is one of the most controversial topics in motorcycle maintenance. Supporters say WD-40 is great for cleaning your chain and won't harm a thing. Critics say WD-40 – or more specifically the petroleum distillates in WD-40 – will dry our the O-rings, displace the grease, and ruin your chain.
What's the truth?
To begin, 'WD' stands for Water Displacement, and the '40' stands for the 40th formula to be mixed up. The safety sheet for WD-40 says that it's mostly Stoddard solvent, a petroleum product similar to kerosene. So for all intent and purposes, WD-40 is mostly kerosene. And most motorcycle owner manuals actually recommend using kerosene to wash your chain.
Okay, but WD-40 isn't 100 percent kerosene, and there might still be something in that secret formula that will cause your chain's O-rings to swell up and die. So, to find out just how damaging WD-40 might be we disassembled a motorcycle chain an dropped some O-rings into pure uncut WD-40 and let them stew for a week.