My B7100 HST-D has the d750a engine. I have the operators manual and the service manual for this tractor. The operators manual states the oil capacity is 3.1 l. The service manual states the oil capacity at 4 quarts. 3.1 l is 3.27 quarts, give or take a spoon full. Which is correct? The stop on the oil check rod was loose and I want to get it set right when the correct amount of oil is in the crankcase. Between the manuals there is 3/4 of a quart difference.