Any reason motor oil cant be used in a damper?

[One Pivot]

Motorex 5w40 specifically.

I needed to thicken up my 5w, so i added maybe 20ml. Went on a couple rides and its fine.. but is there something inherently wrong with motor oil in a damper?

[bad mechanic]

Your fork is going to catch on fire.

[tacubaya]

Works like crap for damping. Why do that when you can get a liter of Maxima oil for 10 bucks? Jeez..

[One Pivot]

Its a shock.. so its under pressure, and shouldnt mix with any air.

Its probably 85% filled with maxima 5wt.. the rest is motor oil. I have 3 bottles of different weight fluid, I figured id use what I already have. If it breaks, ill go buy the right weight

[bad mechanic]

Its a shock.. so its under pressure, and shouldnt mix with any air.

I stand corrected.
































Your shock is going to catch on fire.

[One Pivot]

Thanks bad mechanic!

[Bill in Houston]

two words for ya:
ka
blooie

[tacubaya]

Just don't blame us when your suspension either catches on fire or starts working on an otto cycle... and catches on fire eventually.

[nov0798]

I have used Amsoil 5-40 oil in my lowers for years, and it works fine.

[tacubaya]

I have used Amsoil 5-40 oil in my lowers for years, and it works fine.

[nov0798]

[One Pivot]

I definitely need to get some damped lowers.

[mtnbiker72]

I have used Amsoil 5-40 oil in my lowers for years, and it works fine.

Splash oil is not damper oil...and yes, Manitou even spec's Motorex 5W-40 in their lowers.

Motor oil will foam quicker than specific fork damper, your damper has air in it even if it's sealed. Fork oil has specific additives to prevent this VS the anti-friction and wear additives in motor oil. Otherwise you won't hurt anything.

[Dougal]

No reason it can't. But unless you are stuck in the back of beyond there are not many reasons to do it.

[nov0798]

Splash oil is not damper oil...

You ever have one of those days?

[eshew]

in·her·ent ( n-hîr nt, -h r -). adj. Existing as an essential constituent or characteristic

Like others have said the "inherently" wrong quality of motor oil is that it doesn't have the anti foaming characteristics of fork oil.

If you don't mind servicing your fork sooner then I doubt it's a big deal. If it feels good, great! If it degrades your seals faster or gunks up your fork, oh well.

You should try oilive oil or vegetable oil next time...go green!

Maybe even tanning oil for that nice healthy bonze color

[Clutchman83]

Motor oil in your fork is not going to combust. That's ridiculous. It will work but it's obviously not recommended for the foaming issue.

[TigWorld]

You're not going to get any foaming issues in shock, but the primary difficulty is knowing what the true cSt of your particular motor oil is. For a rear shock the cSt @100C is the key value. If the cSt @100C of your motor oil is comparable to the cSt @100C of the recommended shock oil then its probably an OK way to go if you have no other option.

[Gman086]

Motor oil in your fork is not going to combust. That's ridiculous. It will work but it's obviously not recommended for the foaming issue.

I'm not so sure about that. I think the probability of combustion is proportional to adding moar shimz.

Have FUN!

G MAN

[1niceride]

I just used some brake mineral oil to cut 10w to around 5w for my float last month..still is fine.

[mullen119]

I wouldnt do it just because its a multiweight oil.

[tune]

What's wrong with multigrade oil? Should work better in different temperatures and some oil manufacturers also make multigrade suspension oil: Motorex - Oil of Switzerland - Motorcycle Or did you mean that it's not a good thing to mix standard and multigrade oil?

[PMK]

This is a comical topic. Yes it will foam. In a gas shock it will foam also unless the fluid has been degassed prior to install.

The oil will break down quickly on account of it shearing as it crosses the shims. Will it hurt the fork, probably not.

The fork likely slide very nice and have a good feel in regards to movement, the damping on the other hand will go away if you ride it for any amount of time or with repeated impacts.

Truly, you will be far better off with a bottle of M1 ATF or another quality automatic transmission fluid.

PK

[nov0798]

You could probably also use this. its typically made for motorcycles, but should still work in a bike fork/shock.

AMSOIL - Shock Therapy Suspension Fluid #5 Light (STL)

[One Pivot]

Its filled with about 85% shock oil, belray 5wt. It was topped off with motor oil, not filled with it.