Fork oil query on OEM springs

Quick question -I want to give my fork oil a change. I am sticking with the original springs for now (I know, I know!). Halfords do two Castrol 10w options - one just 'fork oil', the other is a fully synthetic one. I gather from searches on here and elsewhere that the fully synth one is actually much heavier - 42cSt for synthetic and only about 15cSt for the ordinary stuff. So, er, which do I want? And do I just stick with standard air gap?

My guess is that I probably want the fully synthetic one as I find the front end a bit jittery at the moment and clunky over bigger bumps but learned opinions welcomed.

Bike is a 2010 pointy - oil hasn't been changed before so filling them with soup would probably be an improvement anyway! I weigh about 12.5 stone without gear on. Riding is a mix - mostly town commuting and motorway during the week with some spirited road blasts for pleasure. No track stuff.

Why not pop in new springs? Your going to all the bother of changing the oil and missing the simple step of swapping springs?

Fair question, alas the will is strong but the bank balance is weak! Big service coming up too so jobs are being fiscally prioritised.

[embee]

I used the Castrol synth "10W" once, found it very harsh when cold, felt like the forks had a stick of wood in there. Didn't like it.

I reckon you need something with a viscosity around 35cSt (@40C) on the white table about halfway down the page here , which is in the range most 10W oils sit. My preferred oil is Fuchs/Silkolene PRO RSF and I use the 7.5W which is in the 35cSt region. I haven't tried the 10W version with stock SV dampers. RSF is not always that easy to find, but search around. There are some other options in that parish.

Others will give their views I'm sure.

The line on oil level/air gap is, if you like the action of the forks, but they bottom out, add more oil.
Since you don't know what the fork action will be like yet, you might as well start with stock oil level and see what happens.

[Bibio]

silkolene maintain 10w. most bike shops sell it.

Jeez, this is proving harder than I thought! Local places have either Castrol fork 10w - bit light. Castrol synthetic 10w - bit firm. Putoline hpx 7.5 - bit light. Or putoline hpx 10w - looks like probably too firm if the CST rating I just looked up is correct. After all this faffing around I'm probably not going to have time do do the damned things now!

[Bibio]

dont frett, just bung any old 10wt in as it will be way better than the pizz water that is in there. it's a damper rod fork you aint going to tell any difference between cst of the different 10w.

[21QUEST]

hpx 10 if memory serves me right, would definitely feel very harsh.

Any 10W or 'W' with a cst not far off(1 or 2) either side of the Silkolene maintain 10W or RSF Pro 7.5 would be fine.

Where did you find the table for Putoline?

Cheers for all the advice folks. Ended up going for the Castrol synthetic jobbie. Close enough on the side of firm and as lance says, cheap suspension anyway so anything will be an improvement but nothing will make it great!

Oh crap, just realised I haven't got a 12mm hex to get the wheel off - aargh!