17-10-2017, 08:57 AM
Some o f the former more definitive posts cut through a lot of folklore and random notions but are now sadly difficult to find.
Relative the more traditional (now cheaper) multigrades, there is a somewhat theoretical case for monograde 30 in very highly stressed hot running engines. But scores of millions of vehicles including heavy transport , and with bearing loadings vastly greater than a Seven, used older style multi grades with low rates of wear undreamed of years before.
The argument for non detergent oil is
a) it will be less inclined to release varnish flakes, compacted dirt, and sludge blobs from a very dirty engine, with risk of blocked jets.
b) in a clean engine without filter it may leave contaminants as large particles in the sump, hopefully not or seldom circulating, instead of as very fine circulating suspension. I dunno if anyone can find a paper establishing a wear advantage of the former, without filter or with; suspect in the realms of folk lore. Note the late VW Beetle, without filter, and without forgiving white metal bearings ran detergent oils
A non detergent oil if also without all other modern anti wear, ant corrosion additives would be much as the API SB oils of the 1940s, with which Seven mains often rusted out with gusto, and cyls needed boring after 40,000. Not something to pay a boutique premium for.
The degree to which the antiwear additives in modern oils suffice, or whether the high ZDDP of earlier formulations, some of which are available in cheaper grades and in diesel oils, is superior, is beyond me. For many years Sevens had none. Loadings and rubbing speeds in a stock engine are very modest.
As for gearboxes and diffs the debate is usually about EP oil and whether it damages bronze and polishes synchro cones. With many medium grade non EP gear oils and suitable engine oils cheaply and readily available, gearboxes not an issue.
The diff generates debate. Oil makers claim yellow metals not damaged by commonly available modern EP diff oils, but many prefer to use traditional low EP gear oils, which in the heavy grades required to stem leaks and noise, require some effort to obtain. Later Austin publications for the Seven advocated EP oil; whether this less or more corrosive than present full EP oils, and whether or not significant, I dunno. My car, as thousands of others, ran EP for decades and the ball races did not collapse, nor the plain axle bearings vanish.
My understanding is that EP corrosion was/is associated sulphur/chlorine EP compounds.
Catalytic converters are allergic to phosphorus hence ZDDP etc phased out of petrol engine oil.
Relative the more traditional (now cheaper) multigrades, there is a somewhat theoretical case for monograde 30 in very highly stressed hot running engines. But scores of millions of vehicles including heavy transport , and with bearing loadings vastly greater than a Seven, used older style multi grades with low rates of wear undreamed of years before.
The argument for non detergent oil is
a) it will be less inclined to release varnish flakes, compacted dirt, and sludge blobs from a very dirty engine, with risk of blocked jets.
b) in a clean engine without filter it may leave contaminants as large particles in the sump, hopefully not or seldom circulating, instead of as very fine circulating suspension. I dunno if anyone can find a paper establishing a wear advantage of the former, without filter or with; suspect in the realms of folk lore. Note the late VW Beetle, without filter, and without forgiving white metal bearings ran detergent oils
A non detergent oil if also without all other modern anti wear, ant corrosion additives would be much as the API SB oils of the 1940s, with which Seven mains often rusted out with gusto, and cyls needed boring after 40,000. Not something to pay a boutique premium for.
The degree to which the antiwear additives in modern oils suffice, or whether the high ZDDP of earlier formulations, some of which are available in cheaper grades and in diesel oils, is superior, is beyond me. For many years Sevens had none. Loadings and rubbing speeds in a stock engine are very modest.
As for gearboxes and diffs the debate is usually about EP oil and whether it damages bronze and polishes synchro cones. With many medium grade non EP gear oils and suitable engine oils cheaply and readily available, gearboxes not an issue.
The diff generates debate. Oil makers claim yellow metals not damaged by commonly available modern EP diff oils, but many prefer to use traditional low EP gear oils, which in the heavy grades required to stem leaks and noise, require some effort to obtain. Later Austin publications for the Seven advocated EP oil; whether this less or more corrosive than present full EP oils, and whether or not significant, I dunno. My car, as thousands of others, ran EP for decades and the ball races did not collapse, nor the plain axle bearings vanish.
My understanding is that EP corrosion was/is associated sulphur/chlorine EP compounds.
Catalytic converters are allergic to phosphorus hence ZDDP etc phased out of petrol engine oil.