If they did i honestly doubt you would even notice a difference in fuel consumption although you look to be measuring your fuel consumption out to a hundredths of a gallon per hour, You'd probably have to measure the fuel you added with a graduated cylinder and filling to exactly the same point on the tank. It would only really burn more fuel when you were loading it up to the point that it would have bogged down with the reduced power level. especially if the only difference in the motors was in the setting of the injection pump to obtain the lower power level. If you have the same rotating mass, bore and stroke, intake then frictional and pumping losses, will be the same.
Most of the Time My M8540 85hp consumes between a 1/2 a gallon and 3/4 gallon an hour when I'm doing wood work and thats moving around 10,000 lbs plus what ever wood i'm hauling. Brush hogged for 6 hours with a 7 footer and only used between 5 -6 gallons total. I've run a 3 bottom plow through hard ground and i was burning near 3 gallons an hour. Running my hydraulic splitter with the engine at 2100 RPM Burns about a gallon an hour. No bad for a tractor that has a maximum hydraulic output of over 20 HP The point is that diesels only burn burn enough fuel to match the load put on the engine. a 3.8L engine will have more losses to over come than a 1.1L So it will burn slightly more fuel just idling.