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Mark. L #849141 05/17/21 2:49 pm
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@ Rohan. For 20w-50 out of the can, is not the SAE rating "50" because that's the viscosity at 100'C? 100'C being the only temperature at which oil viscosity can be measured under SAE J300. Therefore - after being Nortoned - if the 20w-50 no longer measures as SAE 50 at 100'C then the SAE rating has degraded.

My view is that the "20W" is not the SAE rating, the "20W" referring to "winter", not "weight". Although I'm not certain how it's measured.

Probably needs a Britbiker who works in an oil analysis lab to analyse a number of oil samples from a number of bikes to get a bigger picture. A synthetic oil is the obvious answer where the oil molecules are being chopped up or burnt, but my guess is that there are no synthetic oils with low/no detergents and no friction additives. I couldn't find any after a brief search.

If multigrade does degenerate quickly in a Britbike then back to monograde and 1000 mile oil change intervals! Although perhaps 1000 miles is right anyway if the oil is being contaminated by petrol.

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Dibnah #849147 05/17/21 3:30 pm
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Hi,
Originally Posted by Dibnah
"20W" is not the SAE rating, the "20W" referring to "winter"
not certain how it's measured.
It is one SAE rating, measured at zero oC.

Originally Posted by Dibnah
20w-50 out of the can, is not the SAE rating "50" because that's the viscosity at 100'C?
Yes, but "50" is the other SAE rating, measured as you say at 100oC.

Aiui, 20 is the base oil, it's the VI that make it 50 @ 100oC. As the VI degrade/become chopped up, the oil remains closer and closer to the base 20 even when heated.

Originally Posted by Dibnah
no synthetic oils with low/no detergents
You wouldn't want it anyway.

Originally Posted by Dibnah
If multigrade does degenerate quickly in a Britbike
It doesn't generally. Dunno about every Britbike but aiu the primary reason Triumph and BSA spec'd 1500-mile oil changes in the twins was lack of a proper filter; triples, always with a proper filter, same recommended multigrades as the twins, 4000-mile oil changes.

Hth.

Regards,

Mark. L #849176 05/17/21 10:29 pm
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1971 BSA A65 = 3000 mile oil change interval in the manual.
That's with no filter. 20w50 was recommended so at that time
an SF or SG was the go. (GTX etc , nothing fancy.)
Fit a filter and you are good for 5000 miles before changing.

BSA_WM20 #849196 05/18/21 4:21 am
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Originally Posted by BSA_WM20
To use oil cooling you would need to use large volumes of oil plus have a reasonable sized heat exchanger to cool the oil down before returning it to the engine
Thus, the high capacity of the triple oil pump, and the need for an oil cooler.
Still, some tell me that I need a thermostat on the cooler to bring the oil up to temperature instead of letting it cool the bearings and keep good pressure.
I'd rather have a happy engine than happy oil. The oil is disposable, the engine is not.


It's not a bug, it's 'character.'

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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NickL #849218 05/18/21 9:50 am
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Hi Nick
Originally Posted by NickL
1971 BSA A65 = 3000 mile oil change interval in the manual.
That's with no filter.
Intriguing, thank you.

Wonder why Meriden stuck with 1500 miles? confused

Regards,

DavidP #849222 05/18/21 11:13 am
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Originally Posted by DavidP
Still, some tell me that I need a thermostat on the cooler to bring the oil up to temperature instead of letting it cool the bearings and keep good pressure.
I'd rather have a happy engine than happy oil. The oil is disposable, the engine is not.

Your engine may not always be happy with oil full of condensate water.


Amateur Loctite enthusiast.
Mark. L #849231 05/18/21 1:05 pm
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Quote
Your engine may not always be happy with oil full of condensate water.

Good point, on the two belt drive Ducati 750's I've owned, both had oil coolers but no thermostat. The 750 Paso actually had 2 oil coolers built into the faring whilst the 750ss had one.

The oil temp gauge on these bikes always struggled to reach a decent reading like 100c and as a result the oil coolers were blanked off with pieces of conveniently sized plastic, this led to a small improvement but wasn't 100% successful.

With the oil coolers blanked off it would take a good hours ride at motorway speeds to get the oil up to around 100c and even then the oil level window would still be misty, showing that there was condensation in the engine.

It was only on hot summers days (30c or so) that the oil properly came up to temp and the oil level window cleared.

So I think that what this shows is that oil does need to reach a minimum operating temp of 100c or more to boil off moisture.

Oil coolers can be useful in in warmer climates but in the UK their usefulness is limited by the generally low ambient temp.


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Stuart #849270 05/18/21 11:08 pm
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Originally Posted by Stuart
Hi Nick
Originally Posted by NickL
1971 BSA A65 = 3000 mile oil change interval in the manual.
That's with no filter.
Intriguing, thank you.

Wonder why Meriden stuck with 1500 miles? confused

Regards,

Maybe as they shared primary oil?
(mind you, my a65 does as well......)

Mark. L #849282 05/19/21 1:37 am
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What temperature did the oil reach on T150 and T160 Triumph "Tridents?"
They also had oil coolers.

I have a friend who had several early Tridents.
He had denim covers made to snap over the oil coolers for use in cool and cold weather to get the oil to warm up enough.

NickL #849291 05/19/21 4:25 am
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Originally Posted by NickL
Well, i change the oil and filter on my bikes every 5000 miles whether they need it or not.
Maybe that's why you folks are so concerned about condensation in your oil?


It's not a bug, it's 'character.'

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
92 BMW K100rs "Gustav"
DavidP #849294 05/19/21 4:55 am
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Originally Posted by DavidP
Originally Posted by NickL
Well, i change the oil and filter on my bikes every 5000 miles whether they need it or not.
Maybe that's why you folks are so concerned about condensation in your oil?

Concerned about oil in my old crates? I don't think so!
My average ride is always over 75 miles so any water boils off.
Plus it's normally warm here anyway.
I like the oil to be 80C+ that way it flows well, when i raced i used R30 here
despite the 40C+ the cooler was blanked off most of the time as races were
so short. The outfit i prepare now has no cooler and runs 15w50 or 10w50.
Depending on what's on 'special'.

Mark. L #849303 05/19/21 7:47 am
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Unfortunately, I can't find a free copy of SAE J300 to check for a requirement to measure kinematic viscosity at any temperature other than 100'C, athough the references I can find refer to testing kinematic viscosity at 100'C.

Surprised to see such a touching belief in the manufacturers' recommended oil change intervals. Engine manufacturers generally have minimal interest in engines lasting much past the warranty period. AJS "instruction book" from 1956 states change oil every 5000 miles (unless only used for short journeys), that's with a mesh filter.

It must surely be possible to do a simple check of the SAE kinematic viscosity grade of used engine oil. Heat oil to 100'C on a convenient cooker (wait until your "loved one" goes out), drop ball bearing in and see how long it takes to sink a measured distance.

Mark. L #849304 05/19/21 8:14 am
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I expect to rebuild these engines every 25-30k miles.
I don't believe that by using a fancy, highly priced oil will make
that rebuild interval any longer.
These bikes were slung together on a production line by blokes
who were paid by how many they built, not by tight tolerance control.
They are old workhorses not thoroughbreds.

Dibnah #849309 05/19/21 9:01 am
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Originally Posted by Dibnah
Unfortunately, I can't find a free copy of SAE J300 to check for a requirement to measure kinematic viscosity at any temperature other than 100'C, athough the references I can find refer to testing kinematic viscosity at 100'C.


Multigrades and 20W/50 have been around for more than a half century or more, bit strange to be quibbling about it now !
The 20W part of it most assuredly refers to the room temperature side of things.
Multigrades flow better at cold start times - even the marketing wallahs spruik that.

Oil samples can be sent off for testing.
They report back a multitude of things.
One important one is how much 'anti-acid' is still has left in it.
This is the one that prevents corrosion from the acidic moisture kicking around in it after a cold start.
As every taxi driver and truckie knows - "if it never cools down it never wears out".

Mark. L #849314 05/19/21 10:18 am
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That would be a cold room then. For 20W-50, the "W" (winter) test is apparantly cold cranking at minus 15'C, also "cold pumping" test at minus 20'C

Oil sample analysis in the UK costs substantially more than an oil change for a Britbike, so that's a non-starter for me.

I don't mind a bit of quibbling if it gets me the right oil to avoid expensive and time consuming engine rebuilds.

Dibnah #849322 05/19/21 11:36 am
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Originally Posted by Dibnah
It must surely be possible to do a simple check of the SAE kinematic viscosity grade of used engine oil. Heat oil to 100'C on a convenient cooker (wait until your "loved one" goes out), drop ball bearing in and see how long it takes to sink a measured distance.

Viscosity testing is performed by how long it takes a set volume of oil to pass between points under gravity and open to atmosphere. Depending on how big the tube is depends on what viscosity you use within it (you wouldn’t use gearbox oil in the same tube as you would for a 10wt for example) you don’t want a tube that flows too quickly on a sample as you will invariably not have an accurate result. You also wouldn’t want something that would take all day to test either as time = money.

The said tube is sat in a stirred liquid bath (most commonly of silicone oil) heated to the desired temperature, most commonly 40°c and 100°c are used as bath temperatures.

From the time taken you can calculate the kinematic viscosity, usually given in cP. (how those values relate to what we know as 20w-50 I don’t know).


There’s cold temperature tests also, these can be down to -40°c or less and are performed by a different method.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

NickL #849329 05/19/21 12:49 pm
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Originally Posted by NickL
I expect to rebuild these engines every 25-30k miles.
I don't believe that by using a fancy, highly priced oil will make
that rebuild interval any longer.

Nick- Isn't that mileage just for a new set of rings rather than a rebuild? Do you just mean top end or bottom end, too?

Dave

Last edited by dave jones; 05/19/21 12:51 pm.
Mark. L #849355 05/19/21 4:31 pm
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Me and Hawaiian Tiger Bill noted that in the 70's hard ridden Triumphs needed guides every 15,000 miles and often new rings. This was with the usual 20/50 Castrol changed every 1500 miles or so...My bikes did have air filters.
Like Nick, I don't think expensive boutique oil will really extend engine life...


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Mark. L #849385 05/19/21 9:27 pm
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As reported earlier, the late Gerry Bristow RIP in Crete had 88,000+ miles up on his Mk 3 Commando,
using Mobil 1 15W/50 WITHOUT AN ENGINE REBUILD.
In fact his bike outlived him, sadly ...

Gerry was an oil industry exec, and had used Duckhams 20-40 multigrade from when it first appeared
(pre Commando). And used to exchange oil banter on a number of bike groups.
He and his wife toured Europe on that Commando, extensively.

Whereas my 1st project Commando needed a rebore at 12,000 miles on the speedo, although I knew nothing of its service history.
Or if the speedo was original ...

Back in the days of and before WW2, the British Army was a keen buyer of motorcycles as military (messenger) vehicles.
Part of the contract conditions was that the bikes had to be able to reach or exceed 10,000 miles without requiring an overhaul.
Most factories had to do considerable work to achieve this. No aircleaners then either, mostly.
BSA did considerable work on metals for cylinders, and chromium plated top rings eventually appeared too.
The research went on after the war of course, and multigrade oils eventually appeared.
The additive package is an important part of this.
As every taxi and truck driver will tell you though "if it never cools down it never wears out".

dave j #849391 05/19/21 10:51 pm
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Originally Posted by dave jones
Originally Posted by NickL
I expect to rebuild these engines every 25-30k miles.
I don't believe that by using a fancy, highly priced oil will make
that rebuild interval any longer.

Nick- Isn't that mileage just for a new set of rings rather than a rebuild? Do you just mean top end or bottom end, too?

Dave


Depends on how it's ridden. My bikes get quite a hard life.
Most of these things are 30's -50's technology and are built
to a price. I expect to see stuff worn in 25k miles, not just rings.
I suppose it i rode the old crates gently that interval may be longer
but i like to check big ends and crank/rods etc every 30k anyway.

As for someone getting 88k miles from an unsplit Commando,
I bet it never saw 6k+ rpm and was ridden like an M20 all it's life.

Mark. L #849397 05/20/21 12:04 am
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We've not heard or even dreamt of an M20 that could get to 88,000+ miles ?!!!!!!
Enlighten us !

Especially one that had been on the motorways of Europe.
Although with the missus on the back, it may not have been ballz out motoring, as you say...

It is a big mileage, significant especially because of that Mobil 1 under its belt most of its life.
Shows how big a difference that stuff can be ?

Mark. L #849416 05/20/21 3:29 am
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Ha, i said ridden like an m20.

Yes a big mileage, but i can't see it being due to the oil alone.
If he changed it every 1500 miles it probably cost him more than
rebuilding the engine twice and changing it every 5000.
That gear is $100 a gallon.
Cruising along motorways at steady speeds is ideal motoring for any engine.
Was the motor all standard? Alloy rods etc?
Not downing it or anything but just sticking mobil 1 into a bike doesn't change
everything. I've known plenty of blokes blow up motors using all sorts of oils!

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Mark. L #849424 05/20/21 6:20 am
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Gerry's RIP Mk3 Commando was bought brand new, so it was totally stock standard.
Mechanically. Set up for touring. They have alloy rods as oem.

Thats a big mileage for a Commando, without touching the motor.
I have heard of a few stray others with similar.
"If they don't cool down they never wear out"
Usually they need rings before anything else - but thats mineral oil.
(And a lot of Mk 3's ate their camshaft ?)

He did all his own servicing - lived in Crete !
Oil change intervals with Mobil 1 are 10,000 miles. (?)
This was a while ago, so $100/gal is a modern price.
So 6 gals for the life of the bike, 5 pints per change.

I wonder what happened to his bike ?
Hobot met up with him somewhere.

NickL #849426 05/20/21 6:25 am
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Originally Posted by NickL
. I've known plenty of blokes blow up motors using all sorts of oils!

Amen to that. !

The guys at the wreckers I used to frequent commented that many of the bikes they see that they got in
for wrecking had next to no oil in them, which is why they blew up. !!!
Fair warning there ??

There is a story someplace in the Commando world where it mentions that one of the club guys tried
5W-30 grade in his Commando one ride. Now that would be about thinner than water to begin with.

In a big clearance motor like a Commando, you'd wonder how it would go ?
And the story mentions that the motor blew it all out in short order, and the motor followed suit shortly after !!!

Mark. L #849427 05/20/21 7:21 am
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@ Allan G, my domestic oil sample analysis kit would probably be based on the tube test

https://www.youtube.com/embed/RpzqsgsqCRE?start=113

which should start at 1 min 53 secs. I can use a waterbath to achieve c100'C

"> Mobil 15W-50 Motorcycle Racing 4T Engine Oil 4L <" currently available in the UK for about £42.

4 litres of Silkolube 20w50 SF-rated oil currently available in the UK for about £25

The last gallon of SAE 50 monograde I bought eight months ago was £11

One potential issue with an oil change interval of 10k miles is petrol contaminating the oil, although riding in the heat of Crete would probably evaporate the petrol quickly enough.

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