I crunched some info recently gleaned from this forum and from Classic Trains Steam Glory. I came up with a comparison of fuel costs for a N&W 2-8-8-2 vs. an SD-70. Add some arbitrary assumptions and here are some numbers to consider:
Someone in a recent post suggested diesel fuel consumption to be about 4 gallons per mile. Current price of fuel is estimated at $1.75. At that rate the SD-70 would cost about $7.00 per mile, working full bore.
Classic Trains talks about coal consumption on the N&W steamer at 13.5 tons for 62.9 miles and a little higher for a steeper grade. Assuming a coal cost of $20 per ton, the Y6b costs $4.28 per mile, or $2.72 cheaper than the diesel.
Before we all rush out to fire up our boilers, there is the cost of water to think about. With nothing else to go on, I used the cost of my home water service (Jamestown NY municipal) and came up with $86.47 for the 21,000 gallons of water used by the Y6b. Divide that by 62.9 miles and we have a per mile water expense of $1.38. So the steamer still saves $1.34 per mile in direct operating cost.
It would take a lot of miles to overcome the other operating economies of the diesel, so I guess EMD and GE are safe for now. Anyhow, this was just a fun exercise and I am sure there are lots of ways you could poke holes in it. So have at it and build me up or tear me down.[:D]