If the 16's are pulling 4 times the cars of the 40's, I might suggest actually placing the 40's "online", and seeing how they pull then. 4 times as many cars. (the 40 pulls 40 loads, the 16 pulls 160) Yeah, right. The EMD fuel consumption chart, in my hand, shows a GP-40, with the 16-6453B consuming 163.7 GPH. The GP-16 with the 16-567C uses 114.6 GPH, both measured in run 8. This is approximately 25% higher in fuel consumption, per hour, or one quarter more, which is significantly less, than double. the ratings across the rest of the look like this:
7th: 131.5 vs. 85.3
6th: 99.0 vs. 67.3
5th: 78.8 vs. 50.8
4th: 59.8 vs. 36.6
3rd: 43.6 vs. 24.3
2nd: 25.1 vs. 14.3
1st: 9.2 vs. 6.1
idle: 5.1 vs. 3.7
These ratings are at 60 degrees fahreneit with barometric pressure readings at 28.86 in. hg. Having run both models mentioned, and running them both in MU'ed applications, my experience has been the 40's will out-pull the 16's readily. Even with some seriously low gearing, the weight of the 40's equates to more tractive effort to move the train, and almost double the HP, to keep it moving, once you get it rolling. The 40 you are using must be dying, or maybe one of the trucks is cut-out. The facts don't add up.......
(for Farmall Bob) My chart shows the 40 at 163.7 GPH, with the 12-645E38. The 38 shows 124.1 GPH, with the 16-645E. Less with the 40, more with the 38, even though it's only a couple of gallons. Both series are Dash-2 types, not 'straight" numbers. Regards
(for PVRX) The GP-38-2 fuel consumption chart I have, shows the following numbers:
low idle: 3.5
idle: 4.5
1st: 7.8
2nd: 17.8
3rd: 32.8
4th: 47.6
5th: 64.2
6th: 82.5
7th: 103.3
8th: 124.1
These are slightly different, although the difference could be between Dash-2 series, or due to temp variants, and altitude differences.