I had a Cummins in my previous R62. Very good engine and economical. I now have a Sisu in an R76. Kind of hard to compare but so far I have have not had any issues with the Sisu. It generally uses around 12 gallons per hour at 65% load. I think it is very economical on fuel considering it is 90 more horses than was in my 62. Also, compared to what my neighbors are using for fuel in their JDs and CIHs, I'll keep my Sisu any day.