On my 88' 240 the top 1/3 of the dipstick is rusted. I scraped it off with some solvent and steel wool but it came back within a couple days.

Is there a good way to clean it off permanently or is it worth $20 to buy a new one?

Thanks.

 

If it serves it's purpose leave it be.

 

May want to replace it if you can't read it.

 

if its getting rusty, that may mean there's too much moisture in your oil, which may mean an coolant leak into the oil, which may mean the head gasket is about to fail.

 

I've seen lots of rusty dipsticks. I think it is a by-product of lots of in-town driving without the engine coming up to operating temperature and thus cooking off condensation. If it bothers you, take some sandpaper or a wire wheel to it and smooth it down. Take the money you would have spent on a new dipstick and buy a new flame trap and re-do your crankcase ventilation system as that too can cut down on dissipating condensation in a timely fashion.