Quote:
Originally Posted by Mister Moose
What am I missing here? Any modern ashless dispersant oil, ie detergent oil, will hold particles in suspension and sludge does not form. We are all changing our oil at very short intervals.
Is anyone running straight mineral oil other than for beak in?
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Detergent oil can only do so much. Sludge results from moisture in the oil reacting with combustion byproducts that end up in the oil from blow-by past the rings and exhaust valve guides. Water (and whatever contaminants it has absorbed) does not mix with oil. It settles to the bottom of the pan when the engine is not running. The only way to get rid of this moisture is to get the oil hot enough to evaporate (boil off) the moisture. This moisture comes from condensation and also combustion. Water is a byproduct of burning gasoline, which is a hydrocarbon ("hydro" refers to hydrogen). We've all seen water dripping out a tailpipe on a cold day. Some of this water gets past the rings into the oil.
If a person starts and idles his Model A for 10-20 minutes every couple weeks or monthly in the winter, he is doing more damage than not starting it all winter. This includes corrosion in the exhaust system.