Title says it all, forks need damper oil, and only thing to hand is regular 5/30w synthetic oil for my car.
Should I? Or if not what to use as no spec sheet for forks
I used to blend my own using straight grade car oil and ATF. Tried various proportions to get the desired damping.
If your fork is a cartridge one then I think the oil is purely a lubricant rather than a damping medium unless you intend opening up the damper cartridge.
Personally I wouldn't. Engine oil is for lubrication and cooling, fork oil for damping. They do different jobs and have different additives and properties to achieve it.
What fork do you have? I'm sure you'll find info on the oil needed if the fork is named.
Mine did Exactly the same - but after a strip and oil change they were like chalk and cheese
I used 5wt 20 engine oil as it was all I had to had at the time - have you got the manual for them as there are two baths per leg and one was dry in my case and caused an annoying clunk