Lubrication and the Compressionignition Engine.
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present one of the most thorny problems in connection with the compression-ignition engine is that of lubrication. In certain Instances it has been found that there is a tendency for the lubricant in the sump to increase in viscosity, presumably owing to the heavier fractions of the oil fuel being blown past the piston rings when the cylinders have become somewhat worn. The very high compression ratios employed cause this action.
On the other hand, the experience of others shows that the presence of oil in the combustion chamber serves as an upper-cylinder lubricant and prolongs the life of the piston rings. This, of course, is the reverse of what occurs in a petrol engine, in which the fuel tends to wash away lubricant.
Much research will have to be done in connection with, permissible amounts of wear before operating engineers can usefully assess the life of a compression-ignition engine with anything like the degree of accuracy which obtains in the case of petrol engines.