Kubota M8540 vs M7040 re fuel consumption

[Dieseldonato]

I would get the bigger tractor for a number of reasons given the OPs intended use. It'll be more comfortable for sure, and based on my limited experience pulling an RCR1884 behind the MX and M, it'll probably be more fuel efficient.

It takes the same amount of fuel to produce x amount of power.
The larger tractor will just handle the load better and have more available power with a larger engine.

 

[mcmxi]

It takes the same amount of fuel to produce x amount of power.
The larger tractor will just handle the load better and have more available power with a larger engine.

What about parasitic loss?

 

[mcmxi]

I wasn't referring to you, I was a heavy diesel mechanic for years and an avid fan of the diesel engine. I've put more miles on service trucks then I care to admit. Last one being an 07 3500 dodge with nearly 400k on it when I left service work. Original everything on that engine. Fuel and air system.

I didn't think you were and I wasn't arguing, just agreeing with your point that turbos are very reliable ... in my experience at least.

 

[Dieseldonato]

What about parasitic loss?

I wasn't going to get into that, but yes your correct. Heavier parts, larger transmission ect. All takes more power to move then something smaller. Although it is well known a hydrostatic transmission looses more power across it then a pure gear driven transmission, just the extra mass adds parasitic load to a machine. Good design can help, but you still need x amount of power to just move the tractor and keep it going. This uses some of your available power, and translates directly to fuel consumption.
I actually have an interesting story about parasitic losses with two engines I built at the machine shop. We had an old beater 1500 chevy. 350 v8 automatic. Std rebuild, nothing fancy stock parts were replaced with stock parts. At the same time we were building a 454 for a local farmer. The owner came to me and asked if I had checked the torque load of the engines? I didn't really know what he was talking about, and said as much. He proceeded to grab a beam style torque wrench and a socket and hooked it to the front crank pulley and turned each engine over. (Both were in long block form, no spark plugs in either.) I was quite surprised to see the difference in the power it took to turn each engine over. He went on to explain that larger engines, although typically produce more power, take more power just to keep themselves running. As a young kid just out of high-school at the time I had never thought about things like that. I can't remember the numbers now, it was quite some time ago now, but it was very educational.