Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Shock Absorber What Fluid?

What fluid should I use to top up my 1966 MGB front shock absorbers?

Can't find anything other than "appropriate fluid" mentioned in either my Haynes manual or on the net. I'm assuming that generic brake / hydraulic fluid is OK?

You need sae30 oil. jack oil is ideal.

fork oil for motorcycle, it's ideal, you select viscosity, soft or hard

Thanks guys. I'll seek some out.
M F McKinlay


I use Mobil 20W fork oil. I believe 20W is the 'appropriate" W, people talk of heavier (30W) or lighter (10W) to effect suspension tuning.

I did try motor bike shops here at the time but none were carrying 20W any longer. Seems modern bikes have moved to really light fork oils around the 5-10W max. It is possible that Harley Davidson may carry the 20W (people talk about excessive cost of that), but none of the Japanese or European bike shops here could help.

Mobil were the only oil company here that had the 20W I wanted - and I had to go out to their distribution terminal to get it. Seems that lubrication fluids generally are moving well on from what our LBCs require.

Roger T

Fork oil or the original Gerling or Armstrong is a better choice than jack oil as they contain an anti foaming agent. Cheers - Dave
David DuBois

Mark, If your front shocks need topping up, maybe you should consider changing them. Check them out at Welsh MG, they are quite cheap for reconditioned units. I have heard some people say that the recon units are not very good. I fitted them to mine 2 years ago and they are still fine. I notice you are in Norfolk, where abouts?
Trevor Harvey

Moss sell a specific damper oil for topping up.

I D Cameron

Not all jack oil is the same, and because of this I would avoid it. Without the necessary anti-foaming agents, the oil will develop air bubbles during agitation which will form air pockets within the shock chambers, reducing its ability to function correctly.

Motorcycle fork oil is good, as is the Armstrong shock oil sold by Moss and others. 20W is the normal viscosity. Do not use greater than 30W or you may damage the valves.
Steve Simmons

Somewhat agree with Trevor. If your shocks need fluid, they are leaking. If they are leaking, your better off replacing them. In the US. We have a company that does a fantastic job of rebuilding. Once done, they are guaranteed not to leak.

If you do refill them, remember, there is an air space at the top of the reservoir so do not fill it all the way. The space is for expansion. Filling it will cause the shocks to fail a lot faster.

Good call on the Harley shop - that's where I got 20W fork oil from - none of the local auto supply stores have it, I have already found myself visiting the Mobil depot for less-usual oils and greases - damn those ricers and their 0w-10!!
Curtis Walker

Thanks for all the advice. The reason I'm asking is that I've got my roadster's front cross-member in bits in the garage (it seemed like a good idea at the time...) and when inspecting and cleaning up the shocks for re-painting, I moved the shock arms through their complete range and one is notchy and jumps 20 degrees of arc or so without damping.

The manual says try topping up the oil to see if that makes a difference. I can see when removing the filler plug that there's not much in it and I can't see any obvious leaks.

I take the point about the re-con option, I'm on a budget so I think I'll try the oil option first.

Trevor, I am indeed in Nofolk, I'm in Southery, just south of Downham Market.

M F McKinlay


I just bought a set of exchange reconditioned shock absorbers from Welsh MG for 13.50 each. I've used them before on another MGB and they gave no problems at all.

At that price they can be considered as service items.


Penrite oil sell shocker oil. Comes with a PG wodehouse type lable, very period. Damn good company all the same. Pity they don't do different grades. Mind you I think they only do armstrong shocker oil because the family like British sports cars (I can't fault them there). They can't make much money out of it, if any.
I got mine from Andrew at mg workshops.I use a big syringe to top the front ones up.
And yes motor cycle oil will do. Might even be better, or the same.

Mark, you are probably either low on oil or are running the wrong type, without anti-foaming agents. If the latter, then it is possible you have developed air pockets within the valve chambers and need to bleed the shocks to get them out. It's also possible there is something physically wrong, but I suspect it's an oil issue.
Steve Simmons

Never had a problem with light hydraulic jack oil e.g. from Halfords.

20W is the maximum you should go to, and the Workshop Manual specifically warns that even this should NOT be used in low temperatures, so I wouldn't use it even in England especially on a daily driver, but not if you take it out on a cold, bright, dry, salt-free sunny day in winter either.

A bit of dampness around the shafts is OK, although ideally they should be dry. If it is running down and especially dripping off they should be replaced.

I've had several recon dampers over the years and only one re-leaked after about 12 months (they are only as good as the returned unit) which isn't bad seeing as they are a fraction of the price of new (which weren't available until relatively recently anyway) and not that big a job to change. One I did reject at the suppliers as it exhibited a 'dead' spot near the middle of its travel when waggling the arms up and down very slightly, so always do this when purchasing as well as pushing them through their full travel a couple of times. I'd do that with new as well as recon.

If it is notchy when cold and topped up (drive it through its full travel a couple of times after topping up) then the valve/s is/are knackered. This is pretty-well irrespective of what fluid is used.
Paul Hunt

This thread was discussed between 31/01/2009 and 08/02/2009

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.