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Recommended engine oil


Hi, any recommendations for engine oil for a 74' 850 please? Thank you for a good spread of advice;I think I'll try the 20/50 GTX.


The manual says 20w/50

Personally i use Mobil 1 10w/60.  A bit more expensive but lasts longer between oil changes 


I used 15/40 semi synthetic for some time. It assisted with kicking over but hot weather may demand a thicker oil. I use 10/60 in my MotoGuzzi. However 20/50 and frequent oil changes is probably as good as anything


I use

Motul 20W-50 7100 4T,

I had a good read of this data a few days ago. Surprised to see how many particular oils he would not recommend for a Norton, but glad my choice got good marks. (Castrol GTX).


This got even an better rating than GTX and was in Jim Comstocks top group after the test. My choice these days or the Fuzz Townsend Classic Oils Heritage 20w 50 which has more detergent and zinc if that,s what you,re after. These for both engine and primary on my e start only Mk3

I used Bel Ray EXP 20w 50 semi synthetic after running in the engine on the above mineral oils. Scored very highly in the top group as well, even better with 5% FR3 low friction additive as tested by Jim and this was in my bike during it,s dyno run.

These three oils used for over 24,000 miles since the 2018 engine rebuild but only the mineral oils now as Bel Ray EXP is no longer available in 4 litres.


The oil tests that Jim did are about the best done to date, but be aware that it does not actually relate to 'in use' conditions. An oil used near the artic circle may not perform or last as well in the hotter parts of the planet etc. A 10WXX or 20WXX with ZDDP will be ideal for most and most oil blenders will let you know if the oil contains it as it can cause damage to catalytic converters. 

Those of you with a laser thermometer that were common during the Covid lockdowns may be able to see how hot the tappet tunnel gets, compare it to the area around the spark plug and you will see why it is important to use an oil that will flow quickly when cold, that is the one area of the engine that needs good lubrication when cold and an oil that flows well to remove heat from that area when hot. 

I used an oil that did not do well on Jim's list and surprisingly after 18,000 miles the tappets still showed the grind marks on the face that had been running on the cam, so hardly run in. It still performed well in use. I did this because I can and not afraid of engine damage. 

Try and find a multigrade oil with ZDDP and has a rating that will give protection above 100 C, some will protect at 125 C, they tend to cost a little more being semi synthetic or synthetic but worth the little extra charged. 


I have severe reservations about the usefulness of the test protocol used .Bench tests even when they use real components ,rarely reproduce the results found in fired engine tests. Your best guarentee is the information on the can. The more specifications the oil complys with, the more certain you can be  of it's quality and performance in service.

Castrol 10W60 or the Mobil equivalent are excellent fot high speed/long milage riding, but cheaper 10W50 or 2W50 oils are safe for the rest of us.

Bench tests for valvetrain wear must reproduce the contact conditioons of an engine in service,be repeatable, discriminate berween oils of known field performance and be reproducible. 

This study is well intended but , in my opinion ,fatally flawed.


Did you mean 20W50, Charles?


I still use Morris's Golden SAE 40 Monograde on my Mk3 Commando. Seems fine with virtually no measurable engine wear when stripped at 40,000 miles. In fairness I only use the electric start when the engine's warm or has been running relatively recently. 


I was recommended  (LE) to use straight 40 Donnington or chatsworth, can't remember which now , in my Mk 3 Commando after rebuild in 1989. I took the electric start out. 

All was well for a few years but then with age and sumping I changed to 20/50 and starting became easy again.

Slightly off topic, I'll give my response to the oil pump / history very soon and thank you to all who responded.


Since the Twins have plain big end bearings, they need oil as quickly as possible when starting up. So a multigrade makes good sense.  The Singles have ball bearings which can work happily without direct oil feed for a short while.

Modern multigrades are far more shear stable than they used to be.  Back when 20w/50 first arrived, it soon became 20 grade in engines like the Mini, where the gearbox destroyed the polymer thickeners.  But that's not a problem to synthetics, and probably not with modern multigrades.

But what's the best oil to cling to the cams  to protect them on startup, especially after being parked for a while?  I believe that's the reason why many Inter owners still use caster oil (which is more stable now than it once was).  I'm not suggesting caster oil for a Norton Twin.  Too many drawbacks...


As an experiment with some free oil I have been using 10/40 fully synthetic yamalube in my 99 for a year or two , no oil filter extra magnets . I had an issue with a seriously overheated motor ( carb problem) and was very surprised that I did not seize a piston , I expect a 20/50 would run a bit quieter but am very happy with a high tech oil

In reply to by robert_tuck


Surely if you haven't got an oil filter a basic non synthetic oil without detergent is better for you Robert?  The purpose of detergent is to amalgamate/suspend the particles and and wastes from combustion into the oil where it can be more efficiently strpped out by the oil filter. If you don't have one, the particles will stay in your oil and wear the engine more. When it is stopped the particles can't seperate out into sludge and certainly can't be grabbed by magnets. If you do have one of course its better because it keeps the sump and the oil ways clean. 

Fully synthetic oils have tremendous lubrication properties compared with old fashioned oils but unfortunately all fully and semi synthetic oils come with detergent so all of us with old fashioned engines with no oil filters should stick to old fashioned oil. Castrol GTX 20/50 was always the way to go in the 80's and probably still is!


To clearup a point. The roll of detergents is

a) to keep hot sorfaces clean, especially the lands and grooves of pistons. In so doing they ensure that rings don't stick and that crown land deposits don't cause bore wear.

b) Detergents also neutralise the acidic products of combustion and are therefore good friends to our engines.

Dispersants ,which appear to be easily confused with detergents, keep solid matter from gathering together into large lumps. These solids are mainly soot and sludge. Soot, unless dispersed with strip of the protective anti-wear films formed by ZDDP. Sludge, formed from water and unburnt fuel fragments, will block oilways. So dispersants are important to maintain a healthy, happy engine. 

Hope this helps.


Not quite sure what this sentence means Charles

“Soot, unless dispersed with strip of the protective anti-wear films formed by ZDDP”


Apologies for confusing disperants with detergents, but from all my previous research some years ago and from reading the exerpt from Davids book here (which may have been amongst my reading material of years ago), I'm still feeling that my conclusion of before should stand - modern synthetics aren't siutable for old engines without oil filters.

Perhaps it should be a new thread then but "Which oil is best for an early Commando type engine if it has no oil filter?"

Thanks all


I’d not heard of the BG oil additives before I read the linked article about oil testing. Pity that the base oils don’t incorporate those high performance additives, I guess it’s down to cost?


The  oil in your can consists of about 80% base oils, 13 % performance additives, the rest is anti-foam additives and viscosity index improvers. Base oils are either refined black stuff (mineral)  which comes out of an oil well or synthesised products.

The synthetic basestocks have better low temperature viscosity properties than do refined base oils. So it is possible too formulate oils with a wider viscosity range using them, e.g. 0W40, 10W60, 10W50 etc..

You can't do this with ordinary base oils but you can formulate 15W40 or 20W50 oils.

Synthetic base stocks are easier to protect against oxidation in the engine and so are prefered for long drain intervals and/or high power output engines.

There are no problems with their use in our engines, but if you do not cover high milages and/ or sustain high speeds, then a mineral oil based product is perfectly suitable and cheaper.

There are a number of contributions from industry 'experts' in the back copies of 'Roadholder', but other than trawling through the lot I haven't found a way of rearching them.


I used to find feathers of iron filings on my magnets when running the normally recomended oils. Since using fully synth , not one tiny filing ,  perhaps they have been dispersed to my crank  cavity !.  Time will tell.

Hello Charles, you commented: "There are a number of contributions from industry 'experts' in the back copies of 'Roadholder', but other than trawling through the lot I haven't found a way of reaching them."

If you log-on to the website, go to 'Roadholder' drop-down and you'll find an article index - click 'Title' and this lists everything alphabetically. You can then scroll down and you'll find the numerous entries for 'Oil' - just click on the item you want and it will take you to the edition and open the relevant page(s) for you.

You will see that the index is fairly comprehensive!


Mark Woodward.

In reply to by mark_woodward


Thanks, yoy need patients, but it is all there. Valuable asset to the club .


Found on a Yamaha forum, but I just had to copy it in here...


Q: How many forum members does it take to change engine oil?

  • 1 first-poster to ask how to change engine oil and what brand of oil he should use.
  • 6 to argue over the actual brand of engine oil.
  • 4 to variously agree with them.
  • 14 to share experiences of changing engine oil and how the oil could have been changed differently.
  • 7 to caution about the dangers of changing engine oil and bare skin.
  • 8 to post about the dangers of disposal of old oil.
  • 1 to post about how his dad used it as rust-proofing.
  • 1 to post about the problems of finding oil filters.
  • 7 to post alternative filters.
  • 1 to post a diagram of his method of fitting a remote filter and bypassing the original system.
  • 1 to like his modifications and divert off into electric fuel pumps.
  • 1 to agree and start on electronic ignition.
  • 1 to very forcibly repeat their post about their favourite brand of engine oil and call others idiots.
  • Another 6 to condemn that 1 as incorrect, and rude.
  • 1 to tell THOSE 6 to stop being idiots and see that he’s correct.
  • 5 know-it-alls who claim to have been in the industry and that modern oil harms engines.
  • 1 industry professional to inform the group that the oil is better than it used to be.
  • 1 to recommend a particularly rare oil, tell horror stories about engines blowing up, then reveal he races cars at 1000 mph every weekend and it’s not relevant to everyday use.
  • 49 to post jokes and thread drifts about blonde moments.
  • 2 to post that this page is not about blonde moments and to please take their discussion elsewhere.
  • 1 to agree with them.
  • 11 to defend the posting to this page saying that we all have blonde moments when changing oil and therefore the posts are relevant here.
  • 24 to discuss the merits of synthetic vs mineral oil.
  • 1 to post a link about how American scientists are making car oil out of almonds and cow pats, but which is not relevant to Club cars.
  • 4 to claim engine oil will kill you in so many different ways, including slipping on it.
  • 6 People to post pics of their own engines and filters.
  • 5 People to post "I can't see the pics.’
  • 1 computer expert to repost the photos.
  • 12 people to comment on other parts of the now-visible engines.
  • 1 person to boast of being an EV driver and how we’re all dinosaurs.
  • 2 to report the post or PM an admin because someone said "f÷×$" in reply.
  • 4 to say "Didn't we go through this already a short time ago?".
  • 1 to say "Do a search on engine oil before posting questions about engine oil."
  • 1 Admin to black mark the engine oil posters who took it all too seriously and got personal.
  • 1 late arrival to comment on the original post 6 months later and start it all over again.
  • 20 to give up on the forum and go off to their own garage.
  • 1 person announces they are leaving the group over the engine oil arguments.
  • 1 to reply back that this isn't an airport, so no need to announce your departure.
  • 1 admin to lock the thread.
  • 1 OP who left the club, never having joined but used the forum for free.

Castrol GTX 20w50 back in the late 70’s early 80’s

Read somewhere that a zinc content in the oil is a good spec for the Commando.

I now use Millar oils Classic 20w50 - Code: MILHP20W505L


From Millers Classic Sport range, High Performance 20w50 has been uniquely engineered for classic performance racing with shear stable viscosity index improvers. This product incorporates Millers unique nanotechnology ultra low friction additive system and is formulated with full ZDDP (zinc phosphorus) for ultimate protection. 

  High Performance 20w50 incorporates high quality fully synthetic base oils and modern innovative additive technology, combined with period viscometrics to provide optimum lubrication characteristics for engines manufactured in the immediate post war period through to the early 1980s. High Performance 20w50 is intended for use in arduous applications such as sustained fast road use, track and motorsport. Suitable for operating at 125°C with peak temperatures up to 150°C.


Great!  Another oil thread.  My recommendation; go for a ride; check the oil; add some more if the level is a little low; go for another ride; repeat. Change the oil when necessary.


Oil. ,  yes , good stuff, put some in . With a bike like mine ,a  std 99 (with an intact cam trough) and used in a temporate climate ,, driven with consideration for its age, it probably does not matter what you use . It will cope , more important to change oil when old otherwise your rings will wear out . If however you are thrashing your Combat across Death Valley your 4s  cam ( already resenting being woke up  without the benefit of of a cam bath or splash from a wet sump ) will need something a bit more focused. 


After reading this thread I have re-kindled my research of years ago on the best oil to use (for a Commando) with no oil filter. As Charles and David, who are clearly experts and not just consumers, say there is a lot of confusion regarding detergents and dispersants. So much so that I am still confused even after re-reading all my copied articles!  There are a host of articles that try to clarify point, but many then go on to say that a full flow oil filter needs to be used with a high detergent oil!  As it seems that all oils have a level of detergent anyway and have had since the advent of multi-grades, I am now feeling it might be a mute point anyway.

None of the discussions above actually picked up the "no oil filter" part of my discussion as a technical difference. Does anybody have a recommendation or a point of view? Which oil should I use if I have no oil filter, or do we feel the no oil filter issue shouldn't affect the choice and that changing the oil more frequently should do the trick. In which case price of the oil might be the only issue. 

To throw in a curve ball... After many years laid up, my first few trips last year have left me thinking my rings are stuck in their grooves.  If I switch to an oil with a high level of detergent, synthetic or otherwise, might it help my rings free up, or should I just get the spanners out and get on with it? (or any other tricks)


I bought a filter kit many years ago for my Dommy.  I then read a report of engines seized solid after the steel filter head spigots were ejected from the alloy housings and all oil lost.  My faith in our suppliers  was somewhat diminished . Since then I have done around 30 000 miles on the dommy with no indication of any wear . I have several magnets and an air filter. I would be happy to fit a filter system that did not look like a lash up. 


I would recommend fitting a filter to your early Commando.  The later Commandos got a filter for a reason, better durability resulting from nice clean oil.  My Dominator wears a Commando filter, tucked behind the gearbox.  My Super Rocket got one, too.  The Vincent I am restoring has one from original, but fitted with a felt filter in those days. Pleated paper is the go.

If you are worried about pipe spigots coming loose from the filter plate, there are plates from Feked which have screw-on pipes.  Pricey, mind.

Why do you not want your early Commando to sport a filter?


Castrol GTX 20/50 was the oil grade used as a baseline when other oils were tested.

Rye oils do a 20/50 mineral oil at a very competitive price.

I didn't fit a filter for two reasons. One is because I am of the overall understanding that the very early models which were little more than a modified Atlas engine with a cover over the magneto mouting point and the engine tilted forward, do not have a return system capable of  the additional flow restiction of a filter. The other is just looks. I didnt like the idea of the additional pipes lashed on, remembering that the flow and return pipes on the early model tanks aren't hidden behind the side panel. (although I already have an additional breather pipe lashed on in the same place :) see pic)


Graham...I think Charles is the expert, not I.  I just have lots of books!  But here is another extract which might throw a bit more light on the issues.

Another complication is choosing the filter. Commando had the same as Citroën 2CV. But they aren't on the lists (e.g. Halfords etc) now that we are forced to find spares by typing our registration number instead of looking for a type number.  And there are thousands of types.  I have a filter on my Dommie and I've bought spares from Norton suppliers (RGM in my case).  I just hope they know what they are providing.  Too much back pressure combined with an old oil pump might limit oil return.  It does take ages to pump all the way to the tank when starting up after an oil change, so rockers get no oil for ages.  I usually try to remember to splash them with an oil can first.  And oil the tappet tunnels.

And the pipes are untidy no matter what I do with them.


The excerpt starts with "typical statements" we often see on the Internet 


A good idea, when you do change the oil on a Commando, is to replace the drain plugs, add the correct amount of oil but leave the filter off.  Start the engine and use a container to catch the oil coming out of the filter housing; the oil will be dirty, often for up to three-quarters of a minute, then the clean oil will begin to emerge.  Stop the engine, wipe the housing and fit the filter.  Re-start and run, then after a while, add more oil to bring it up to around the half-way mark on the dipstick [and you do all have the correct dipstick - don’t you?].  You will need an assistant to help with this method; ask them to kneel down and view the oil flow while you are holding the throttle.  Good luck!


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