ShinerBock wrote:
On the right is the BSFC of the new 2019 standard output Cummins with a higher compression ratio. Its sweet spot is much larger than the 2018 and it would be even more advantageous to tow in 5th at more speeds and loads than 6th if you had a 3.42 axle.
When that engine is working at 1800 rpm and just up to the dark blue sweet spot as you call it it is putting out a minimum of 150 horsepower. (440 lb ft of torque) According to the graph it would be burning 7 gallons of diesel per hour. Assuming you’re towing at 65 mph you’d be getting 9.3 mpg. So in order to be in the dark blue you’re working that truck . The dark blue represents 6.2 to 9.8 mpg at 1800 rpm and 65 mph. I would expect when you’re down at that kind of mileage the automatic is going to be selecting 1800 rpm over 1360 rpm.
Edit: I didn’t do the math on whether or not you can get a tire size and final drive ratio to do 65 mph at 1800 rpm. If you’re only doing 60 mph at 1800 your fuel economy is going to be about 10% worse to get into the dark blue of the graph.
