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oiling the blower

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Just had a small blower motor repaired, with re-made sleeve bearings. The motor repairer suggested 20W engine oil as the correct grade for lubrication. From another source, I heard that synthetic oils contain detergents which can cause bearings to break up and that mineral oils are therefore more suitable. Anyone out there with a view on this ?

 

Thanks. H.

 

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A problem that can arise with lubrication is where bearings can have cages which are attacked by some of the additives in more modern oil formulations. The vintage car side of things usually tries to avoid having modern formulation oils in contact with original pre war bearings in gearboxes and back axles. I think you'll find it is the additives which cause the problem and not the detergents. The detergents wash out dirt which can have accumulated in the likes of an engine and the dirt, which may have lain unmoved for many years, then causes problems by blocking small oilways. This is unlikely to cause any great difficulty in lubricating a single simple bearing.

 

The additives, however, can actually attack the metals within older bearings. These additives are usually found in gear oils (particularly for Hypoid axles) as opposed to engine oils and an SAE 20 oil would be a light lubrication engine oil. When you say sleeve bearing I take it you mean an "Oilite" type of bearing made of bronze which allows oil to pass through it to the shaft inside, as opposed to a bearing with rollers or balls. It is the latter which are most susceptible to additives.

 

An SAE 20 oil is what Rolls Royce specified for their chassis lubrication systems and I would have thought would have been a fairly safe bet for most bronze bearings. It would be commonly used as well for lubricating the bearings on dynamos, magentos and the like.

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