Every time I come to do a lowers service on a new set of forks I find I "need" different oils to the last set. I'm trying to get better about doing lowers services between full paid for services again.Â
2025 Fox specs are "FOX 20wt Gold oil for the air side and FOX 4wt oil (which replaces older 5wt) for the damper side. The standard, modern Fox 36 volume is 10cc (or mL) in the air side (left) and 40cc (or mL) in the damper side (right)
Usually someone has worked out which oils Fox are reselling at a markup - has anyone seen this for the current oils? Â and how critical is it? Â I've got a few somethingÂ
I seem to remember years ago the thinking was you could use almost anything in the oil bath as it was just lubrication but last thing I read suggested it was important as you get some bleed past seals into the oils in the damping circuit. Â
 I've currently got, all years old (does this stuff go 'off'?)Â
Torco RSF racing shock fluid Medium labelled 'fox'
Torco RFF10 labelled 'Rock Shox 15'
Torco RFF 7 labelled 'Rock Shot 5'
Torco MTFR (motorcycle transmission fluid) labelled as 'foam rings'Â
If you have a grip damper fork (instead of fit4 which uses bladder) you need the 4/5wt oil as its shared with damper.
I don't think it matters so much for the other leg but i use Fox 20wt anyway as its really good.Â
FOX 4wt oil (which replaces older 5wt) for the damper side
Usually someone has worked out which oils Fox are reselling at a markup - has anyone seen this for the current oils?
Motorex 4w
As Horatio said the Grip damper constantly sucks up (and expels) oil from the lower leg, so it needs a suitable oil. But Fox said "It absolutely has to be this one specific oil and if you use anything else it'll ruin everything, only this oil is suitable, we mean it" and then they discontinued it and said "Yeah just use this other completely different oil BUT if you use anything else it'll ruin anything, only this oil is suitable, we mean it"
