Luftwaffe and Allied Air Forces Discussion Forum - Daimler-Benz Cold Weather Start Feature

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But how could the Finns justify mixing lubricating oil with aviation fuel knowing this procedure would seriously degrade the lubricating qualities of the oil and thus seriously shorten engine life?

Hi Harold,

That is not the case at all. In fact, it extends engine life. When the temperature drops below a certain point, the higher viscosity oils used in aircraft such as 100W become extremely thick.

This causes a number of problems. First the oil pressure is so high that it would damage the engine. Most airplane engines over come this by bypassing the oil pump by returning a portion of the oil directly to the sump until the oils viscosity reaches a point it will flow properly.

During this time, the wear and tear on the engine is higher than normal.

One of the ways to overcome this is to blend a multi-viscosity oil. Today we have several blends to choose from the most common being 15W-50.

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The advanced additive package in AeroShell W 15W-50 provides excellent protection to engines operating at extreme ambient temperatures.

http://aeroshelldirect.com/aviation_oil.asp

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Multiviscosity oil is formulated by mixing oil with a cold-weather viscosity and oil with a warm-weather viscosity, to which polymers are added. This process allows the oil to function across a wide range of temperatures. This versatility makes multi viscosity oils, like the Phillips XC Oil, ideal for all-season use.

http://www.skygeek.com/48250.html

This is what is being done using the properties of fuel in the winter starting systems. Thinning the oil allows the oil pressure to remain within limits that will not damage the engine. The oil system is then able to circulate the oil from the start and as the engine warms up, the fuel evaportates returning the oil to its higher viscosity required at the higher operating temperatures.

It extends engine life and reduces maintenance.