Motor Oil - Fossil or Synthetic

Alan J

Well Known and Active Forum User
VOC Member
I'm with 20\50 oil=if you use something "odd" it becomes a problem when "touring"-don't all rush to tell me your"vin" uses no oil!!
 

Howard

Well Known and Active Forum User
VOC Member
I do agree Alan, but don't you find 20/50 has become "odd" in most parts of Europe these days.

John

Yes. It seems to be a dying breed, that's why I sometimes go for the 15/40. As I understand it, it's as thick as the old 40 monograde at operating temps, but easier on the starting leg when cold.

H

ps Alan - my Vin used no oil for years............... then I put it back on the road.................
 

John Appleton

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VOC Member
Howard, you are exactly right! When an oil manufacture gives a specification of 40 as a viscosity, this is measured at working temperature,and how many of our bikes get the oil to that happy situation, but is just what a rattly old engine requires at times-BUT, at start up this old rattler has to rely on oil being fed down a long, cold tube from a very effectively air cooled tank, squeeze it through a felt or paper filter, force it through small feed holes into big ends, cam spindles and rocker feeds, and finally rely on enough of it running back through the crank case scavenge hole to keep the return pump happy. Couple this with the fact that heaviest engine wear takes place during cold start up due to surface drag, and a 10 weight oil would be a much better option, and this makes a 10/40 an ideal choice. You can also buy it anywhere.

There used to be an advertising slogan for paint that read "say dulux to your decorator." I think a similar word should be said to an oil rep that says an oil type is "too slippery", or in other words "too lubricatey". I think the point he may have been trying to make was that a new engine will naturally be used under light throttle settings, and with a super oil installed, this can lead to bore glaze, but I have never experienced this on any of our Vincent engines.
On a slightly different subject, but allied to bore glazing, I have read with interest a recent thread regarding the "lapping in" of poorly finished piston rings. It has been suggested that working them up and down the bore with a lapping compound might be a good idea. It isn't. Any engine machinist worth his salt will ensure that his honing marks left in the bore will be at a specified angle, to ensure that "shelves" are formed for oil to sit on to assist ring sealing and lubrication during start up. This angle is usually set somewhere around the 40 degree mark. Too flat and excess oil is retained. Too steep and the oil runs off or is scraped off and will lead to poor sealing and excess bore wear. Lapping a poorly fitting ring into this bore effectivly undoes a lot of your machinists work,and if any of our mechanics should resort to this action, he would soon be after another job!!

John
 

Alan J

Well Known and Active Forum User
VOC Member
Yup!-20\50 is not always available-15\40 is no doubt a good choice![or 10\40-you can often get straight 30 in any supermarket, for lawn mowers] I once put some 2-stroke oil in when I was desperate!
 

Howard

Well Known and Active Forum User
VOC Member
Yup!-20\50 is not always available-15\40 is no doubt a good choice![or 10\40-you can often get straight 30 in any supermarket, for lawn mowers] I once put some 2-stroke oil in when I was desperate!

Halfords sell an oil for older engines (it says so on the tin), It's mineral, I think it's 20/50 and it comes in a tin can, not a plastic bottle, so it looks right in the garage. I've used that in the Vin (I think that's what I'm using at the moment). I think Halfords have a reasonable reputation to protect, and I change it frequently, so I've had no bad experiences with it.

H
 

ET43

Well Known and Active Forum User
Non-VOC Member
I have ever only used a multigrade oil once, it was Duckhams 20/50 and I have to say that I have put litmus paper into a similar coloured fluid that was thicker! Up to the time I dismantled the red thruster I used sae 30 in the winter and sae 40 in the summer. This is because I had read somewhere that big end roller bearings chopped the polymers around in the thinner multigrade oil, hence the use of monogrades' , but a good friend, late of the oil industry, tells me that this is not true of modern oils. Can anyone confirm or deny this please? I remember Phil Irving saying that if one used the machine for short journeys, then sae 20 would be fine.
Now then Sonny, let's be 'aving the truth. ET43
 

Howard

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VOC Member
Phil, you're right, 20/50 is a bit like Budweiser when you pour it in. It's only 20 grade cold, but when it heats up it doesn't get much thinner, so that when it gets to engine temp, it's still as thick as a 50 grade at that temp. Straight 40 is fine for long distances, but we "once around the block" merchants are doing a high proportion of the miles before the oil heats up properly, so we're probably running closer to PEIs sae 20 with multigrade.

Rollers breaking polymers is interesting. I was told multigrades were designed for Mini engines where the gearbox shared the engine oil, if gear teeth don't break them I can't see rollers doing it - like you I don't know where I read that - I'm trying to think of an excuse, but it's probably old age.

H
 

John Appleton

Well Known and Active Forum User
VOC Member
This is because I had read somewhere that big end roller bearings chopped the polymers around in the thinner multigrade oil,
Now then Sonny, let's be 'aving the truth. ET43

Phil, I just know I am going to regret this but.....oh well. This is , or was, to a certain extent true but had nothing to do with the viscosity of the oil. All oils have a package of additives mixed in with a base oil to produce the products that we buy. Broadly speaking these base oils fall into one of three categories. Category 1 is a refined crude, Category 2 is a bit more refined. Category 3 is one of the "synthetic" or designer bases. The additives which give the various characteristics are of a volatile nature, and gradually burn off causing our super oil to gradually revert to the base oil. It will no longer be 20/50, but may well come down to , for example, 25/30. More importantly for those engines having flat cam followers is the fact that, as these additives disappear so does the amount of Zinc dialkyldithiophosphate (ZDPP) in circulation. Zinc phosphate is the stuff that prevents metal to metal contact when two componants put a high shear load on the oil.
Prolonged use of an oil does however improve its friction reducing characteristics, but there is , or was, a field of thought that said putting it through rollers would undo this good work by reducing the length of the previously lengthened molecular structure. So where does all this twaddle leave us.
Thin oils are known to have better lubrication qualities, as an oil, but if we go to a super thin oil as used in modern cars, then we know some of them will have a reduced ZDPP content as it has a detrimental effect on catalytic converters.
If you wish to be really pedantic I suppose you should be looking for a 10/40 oil, of SG rating and having something in the region of :- calcium 0.2% phosphorous 0.110% zinc 0.112 % sodium 0.050% , and change it at 3000 mile intervals.

On the other hand you could always do what the rest of us do and use what you know works, or ask somebody who really knows what they are talking about, cos I am as confused as the rest of you.

Phew, its beer o'clock---I'm off John
 

Tom Gaynor

Well Known and Active Forum User
VOC Member
Trevor Southwell, not nicknamed Clever Trevor for no reason, once took the oil temperature of every Vincent arriving at a big rally. Some had ridden 40 miles, some 400. He presented the information, without revealing the source, to "an oil expert" and asked what he'd recommend. The recommendation was SAE 10, maybe 15.
The only way to get Vincent oil up to the kind of temperatures that avoid emulsification, is to lag the tank. Or use SAE 10.
In the glory days of AMF, bringers of "shareholder value" to HD, with the inevitable disastrous results to quality, someone floated the idea that high quality oils caused Harley big-end rollers to "skid", resulting in failure, because the oil was "too slippy". You may already be thinking "how could anyone be so stupid?". I remind you that half the population are below average intelligence. I make no comment on which end of the intelligence spectrum was someone who bought an AMF Harley likely to be.
This I believe started the belief that thin oils caused cranks to fail, not AMF's piss-poor quality. But a long running, now alas dead, Vincent owner, "The Awful Dave Williams" ran his twin on Esso 0-15 SAE fully synthetic, for thousands of miles, and arguably the UK's leading vintage (essentially pre-1930) Sunbeam guru, is loud in its praises.
I use straight 30. Now that winter is here, it is time to change to something lighter. I think I'll go the Esso (Exxon) route.
 
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