Mixing Motor and Suspension Oil?

My Magura forks want a few ml of SAE40 oil in each leg for lubrication, and a few ml in the air chamber for curve tuning, but I can’t find any suspension oil heavy enough in local shops. However, I have some monograde SAE40 Motor Oil to hand, which doesn’t have much info on it.

Will bad things happen if I use this motor oil?

I have mineral engine oil in my Rockshox Dukes and they are fine

Thanks Edric! That’s reassuring to hear.

I’d wait for a few more recommendations…bad things could happen!

I wouldn’t do it personally…suspension oil has anti-foaming agents in it for a start. And a couple of people I ride with suspect their habit of adding a few drops of chain lube to their stanchions is the reason they’ve worn the anodising off the legs, whereas mine of the same age are fine, difference being I add a few drops of suspension fluid rather than chain lube.

If it’s not cycling through a damper, it will be fine. I use suspension fluid in the damper leg of my forks but motorcycle engine oil in the spring side. It clings and lubes better.

And a couple of people I ride with suspect their habit of adding a few drops of chain lube to their stanchions is the reason they’ve worn the anodising off the legs, whereas mine of the same age are fine, difference being I add a few drops of suspension fluid rather than chain lube.

Sorry? You can’t just say this crap and not explain yourself

Thanks for the replies

It should stay separate from the actual damping circuits, although I’ve read the oil in the air chamber can makes its way past the piston and into the main damper, over time.

With my experimental hat on, I tried mixing a few ml of Finish Line 5wt and this 40wt motor oil in a can to see what would happen. It appeared to mix pretty well, and not separate when left to sit, so I think the (at most) 5ml in the 120ml in the main leg shouldn’t make too much issue.

Seals and things should be ok? Not really sure what motor oil encounters normally…?

Unless you can establish its fully synthetic, your run the risk of it potentially rotting or swelling your plastic parts and seals.

It’ll depend exactly what parts it comes into contact with and what they’re made out of.

Hmmm, even though Finish Line suspension oil is Semi-Synthetic?

Someone here thinks they have 30wt shock oil, so I may go with that instead, if indeed they do have some.