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 MGA - Carburettor damper oil

I read somewhere that Mr.John Twist of University Motors recommends using 90 weight oil for the carb dampers. The design engineers at BMC recommended SAE 20 oil. Now there is a massive difference between the two. Does anyone here use the thicker oil, or maybe has used it in the past? Will the engine run better with this oil? What are the advantages if any? Any comments will be appreciated.

F Camilleri


I have used SAE 30 in the past and thought that was a bit heavy. I use the lightest I can find nowadays. I would have thought the pistons would barely move with 90 grade.

Steve Gyles

Frank, I did try some 85 grade rear axle oil in mine a few years ago. I can't remember how it behaved, but I do remember not liking it and taking the daspots off to clean the stuff out of the damper tubes. I use the genuine SU damper oil now
It comes in a handy little dispensing bottle so you can put just the right amount in. It's only straight 20 and pint for pint, it could probably be bought cheaper, but the convenience is worth the modest price.
Lindsay Sampford

I've always used the SAE20 damper oil as recommended with no problems. I reckon back axle oil is for back axles Frank!
P N Tipping

I remember years ago John recommended just using the same oil you had in the engine. I now use oil for the purpose from Little British car company
gary starr

I expect the 90 wt. oil refers to gear oil which is about the same viscosity as 30 wt. motor oil.

This question of oil viscosities comes up regularly.
John DeWolf

Hypoid 90 oil should definitely NOT go into the carb dampers only in the rear axle. The recomendation is a "thin oil", which in the 50's and 60's probaly meant sewing machine oil. Personally, I have been using ATF for many years and this seems to work fine.
P. Tilbury


For a B according to my drivers guide: SU HS4 is 20w50 summer. You follow the same grade than in engine. An extra: I have owned many Volvos with SU and Stromberg and they recommended ATF fluid. I used this automatic trans. fluid for many years and I am greatly satisfied with it. It is not difficult to imagine I do not drive my car in winter here...


Jean G.
Jean Guy Catford

Well, I replaced the oil in the dampers with SAE 80/90 yesterday. Not tried it on the road yet. It's a nice morning so I'll be going for a drive this morning and see if I notice any significant difference. I will report back.

F Camilleri

I have always used engine oil (clean!)- usually 20/50 - ever since I have had MGs ( since 1968) - seems to work well. Did try 3-in-1 once from the little oil can - seemed to get pushed out too easily.
Cam Cunningham

Just got back from my Sunday morning run, and now reporting on the use of 80/90 in the carbs dampers. Never again will I use such thick oil in the dampers. Acceleration was very sluggish, and the engine seemed as though it needed a rebore badly. Idling was also abnormal and the engine sputtered at low speeds. Tomorrow first thing I shall replace the oil with the usual 20 wt as recommended by the car makers. Now you have it.

F Camilleri

Here's an extensive treatment of dashpot oils by Keith Calver. See here:
JM Morris

Put 90wt. in the mgc hs6 carbs the car was faster on acceleration left it in there,put it in the mga carbs it did not like it not as fast on acceleration,went back to 20-50 oil, my experience with it.
bp perry

Frank I've tried everything from 3 in one oil, ATF to 20w50 engine oil and have found that the 20w50 works the best. BTW the viscoity of 90 weight gear oil is similar to 30 weight engine oil.

Andrew Preston

OK, I'll join the fray:>) I am also in the 20W-50 camp. I have used it in my '73 MGB since new as recommended in the owners manual and also in my restored '57 MGA 1500 since finished in 2003. I believe it is perfect for the application.


Thanks for all you inputs. I thought I will try 15/40 next and see how it behaves. After that I shall also try 20/50 and make comparisons.

F Camilleri

This thread was discussed between 12/02/2011 and 14/02/2011

MG MGA index

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