Personally, I wouldn't use WD40 on any element that would require lubrication. WD40 washes away all lube and is more of a cleaning thing. As good as it may be for fixing seizures, this isn't really what you should spray a piston with. I guess even engine oil would be better for this purpose, best thing you can lube it with is silicone spray or silicone grease. edit: WD40 doesn't corrode the seals of the HS33. I know many people who run it as brake fluid and it works beautifully Great guide though!