So just yesterday i changed my fathers oil in his 2008 Chevy Duramax 6.6 Lmm.. I had a 4.5gal drain pan and it ended up overfilling and i spilled oil everywhere. Had to get a small bucket to get the rest. Put the old oil back in gallon containers and measured 4.5 gallons (18 quarts) excluding the oil i spilled. What the hell just happened here? He told me the oil was changed about 4 months ago but i wanted to change it cause it was so black. Anyone know why on earth it would have almost double the amount of fluid in it?