Changing engine oil in Cummins ISC 350<br/>Can someone explain why the oil fill capacity discrepancy between the Foretravel manual (20 quarts) and Cummins spec sheet (inside the manual says 6.3 US gal). My effort is to also calibrate the dip stick during the process as mentioned on the forum. At 20 quarts the dipstick says that I am 4 quarts low so should I assume the...