18-10-2017, 08:28 PM
The book Which Oil is about the only easily readable text available. But the author seems to be an interested observer, not an up to the minute lubrication industry development engineer or chemist. He labours the sheer down tendency of multigrades, not now considered a major problem. But he does not mention at all the dynamic (fleeting) reduction of viscosity under high shear, the curious and more contentious characteristic of traditional multigrades.
And the oil change periods recommended are incredibly frequent for engines with filters..
The book includes interesting graphs of viscosity of multi and mono grades at various temps (although care necessary with the scales).
I run a 1960s 1600cc Brit car. At 30,000 when I acquired it in 1987 it exhibited marked blow by. Medium quality oil has been used changed at 6,000- 8,000 miles. By 175,000 blow by was serious although little oil used; top rings found to be broken. Bore wear about .004 max. I wonder what it would have been with more frequent changes? Just how long are engines required to last?
Through the 70s and 80s I ran a Jowett Javelin. As is common, oil consumption was generous so for years I used a cheap re refined 30/40 oil which the makers claimed to have no additives. The engine internals were jet black with varnish; running was near ideal but bore wear seemed relatively rapid, although crank and cam wear, usually common problems, very low.
I suspect the main concern with Sevens is to avoid crankcase condensation potentially damaging to the roller bearings. Avoid brief starts. A thermostat might achieve more than very frequent oil changes
And the oil change periods recommended are incredibly frequent for engines with filters..
The book includes interesting graphs of viscosity of multi and mono grades at various temps (although care necessary with the scales).
I run a 1960s 1600cc Brit car. At 30,000 when I acquired it in 1987 it exhibited marked blow by. Medium quality oil has been used changed at 6,000- 8,000 miles. By 175,000 blow by was serious although little oil used; top rings found to be broken. Bore wear about .004 max. I wonder what it would have been with more frequent changes? Just how long are engines required to last?
Through the 70s and 80s I ran a Jowett Javelin. As is common, oil consumption was generous so for years I used a cheap re refined 30/40 oil which the makers claimed to have no additives. The engine internals were jet black with varnish; running was near ideal but bore wear seemed relatively rapid, although crank and cam wear, usually common problems, very low.
I suspect the main concern with Sevens is to avoid crankcase condensation potentially damaging to the roller bearings. Avoid brief starts. A thermostat might achieve more than very frequent oil changes