There can be a lot of variables that goes into oil volume. There are a lot of owners manuals that will list a certain volume, but what they don't tell you is that volume is for a dry unit, and after the oil has been added once, the new volume may be less. I have an engine that the manual calls for 78-80 ounces, and has taken exactly 64 ounces to reach the full mark its entire life. The front axle on my tractor has a sight glass to check proper level, and after an gear lube change will show full, and sometime in the next 50 hours of operation it will disappear off of the sight glass, and you will need to add another quart, it takes that long to work the air out of the final drives, and there may be pockets in your hydro system that will bleed out at a later time.