Mobil 1 car oil did not test well ( failure at 134lbs load) in some recent scar testing done by Jim Comstock at the Norton site.
The Mobil 1 vtwin 20/50 showed a little higher ability to lubricate under pressure( failure at 178lbs load)
Castrol Classic XL 20/ 50 ( non synthetic) tested very well and is cheap enough to change often.(failure at 331 lbs) It is also very low friction for a conventional oil.
It's readily available in the UK at 25gbp per Imperial gallon. Unfortunately I haven't found it here in Canada. You might have better luck in NZ.
It is specifically blended for use in our old pushrod type engines ( right amount and type of zddp)
So not the most modern oil. It wouldn't be ideal in something running a catylitic convertor, but the modern low zinc oils generally aren't ideal in a scrapey old pushrod engine such as the A10.
Here is Castrol's description of Classic XL.
I like the tin!
https://www.castrol.com/en_gb/united-kingdom/products/cars/classic-oils/classic-engine-oils.html
Glen
Well Glen,
Go back & read Gerry's article then read paragraph 4 in the one you linked to.
The Castrol blurb is once again talking BS about detergency .
The Castrol article is also talking rubbish about oil gallery sizes.
The same amount of strait 50 will pass through an oil hole at working temperature as 20w 50, 10 w 50 or 5w 50 because they all have the viscosity of 50 at working temperatures.
The only down side of a multigrade is it is thinner when cold so will leak more in the shed.
Some have mentioned that the oil gallery for the cam on A series gets it's initial fill from the OPRV opening in the first few seconds when the thicker multigrades overpressureize before oil has been flung around inside the case and has had time to drip back down into the cam tunnel.
In reality it is a lot of gum flapping about very little.
Back in the 60's & 70's when I was an impoverished student my A10 ran on supermarket 20w50 without much in the way of problems.
It took me to uni, then to work then home then back to uni again. It took me on holidays, down the pub on weekends after work and on the occasional long weekend ride.
The oil was rarely ever changed, just topped up.
Decades latter when there was more than one number in my bank balance before the decimal point, I went over the BP Coarse + 30 or 40.
That was followed by Penrite in various viscosities. Followed by Targa Enduro Lube, agai because I got it cheap and the 2 litre flatish bottles packed rally well when I went away.
Thinking back, heavier oils made little difference apart from dribbling a little less when parked.
When we ran the courier company everything used Western Oil 20w 50 because it was cheap & we bought it in 44 gallon drums.
Now I fix mowers and everything runs strait 30 mower oil again without oil problems because I can buy it wholesale.
Considering the sort of useage our old iron gets now days I seriously doubt any oil would cause a problem provided it got changed regularly.
People go on about zinc as it it is some sort of magic ingredient .
A higher zinc content is vital, it you are on a drag strip, running gapless rings in a blown engine with extra high lift cams and triple valve springs.
A 7/10 camshaft runs in an oil gallery and the loads on the followers& cams are quite moderate when compared to a modern DOHC engine spinning at 9,000 rpm
From memory the valve springs in a series are around 90 inch pounds , please correct me if that is wrong, so any oil that gets to better than 100 is more than good enough.
And lastly, as people seem to be besotted by oil test results, not one of the standard oil tests mimicks what is happening in your engine.
They are all way more stressful than will ever happen inside you crankcase.
Their job is purely to allow blenders to compare one batch to the next and to evaluate a change in formulation
