Posted by Willy-N on Thursday, December 08, 2005 at 11:25AM :
In Reply to: What is the point at which diesel congeals? posted by Jerry Henry on Thursday, December 08, 2005 at 10:49AM :
Number 2 diesel fuel begins to cloud as the ambient temperatures drop toward the freeze point, 32 degrees F (0 degrees C). This clouding is the result of the wax (paraffin) in the fuel solidifying. As the temperatures drop below the freeze point, the paraffin molecules combine to become solids in the fuel which eventually become large enough to be stopped by the media within the fuel filter(s). This is commonly known as the gel point which generally occurs at approximately 15 degrees F (-9.5 degrees C) below the cloud point. The wax will then begin to form a restrictive coating on the filter media which results in a loss of engine power. The same process occurs when starting a cold engine with the ambient temperature below freezing. The fuel filter(s) media becomes almost instantly coated with a restrictive layer of wax. Usually, enough fuel can pass this layer to allow the engine to idle, but not enough fuel to allow the engine to attain operating RPM.
There are additives to help stop this from happening along with using winter fuel sold in areas that get real cold. Problem is when leaving a real warm area where you bought your fuel and driving into a sub cold temp area you may have gelling problems due to the wrong winter mix for the engine. Mark H.
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