Geoff, depends on who you ask
. Simple answer is Yes. Clifford gives me a hard time about my fuel saving calculations that don't offset the need to buy a second Series 60
As you recall, you helped me a lot to get my 6V92 up to 350HP specs. Then I took it in to have it smog tested (required dyno test in the Denver area) and on the way home the water temp. was well within limit one second and then huge amounts of white smoke the next second. Pretty sure the emission folks did not set up a fan on the radiator and overheated the engine and that resulted in a cracked head.
When the engine failed, I did a lot of thinking. I could have lived with the 350 HP but it would have been very marginal in our mountains and I had planned to tow some big vehicles (largest was my service truck at 9000). But for the cost of having the engine rebuilt (estimated $8K which might have been low), I purchased a Series 60 and Eaton AutoShift. I had to add maybe $2-4K more in parts and endless hours to get everything bolted together. Did all the work myself.
If I had had to pay $40K to have someone do it, the answer would surely be different.
Unfortunately I was stupid enough to believe that all Series 60 engines are million mile engines (this from a person who had to deal with a lot of statistics in my career
). I got about 60K miles out of first engine (about 700K miles total as I recall) and then had cylinder sleeve sinking problems. My second engine is fantastic and the bus drives like a dream. Hardly knows what hills are.
In my engine conversion article for BCM I estimated my fuel savings as follows:
The only factual data I can present is my own situation. Our bus and toad weigh over 46K pounds (large toad). I have driven the coach over 52K miles and have averaged 7.7 MPG as measured by the SilverLeaf (directly off the engine ECM). I did not have any experience with the bus at this weight with the 6V92, but my best guess is that I would have gotten less than 6 MPG (remember we travel over the mountains a lot and weigh more than many buses). If the 6 MPG is close to being correct, my mileage improvement is close to 30%. Over the 52K + miles, I have used about 6,800 gallons. If I had used 30% more fuel that would have been an extra 2,000 gallons. Even at a conservative $2.50 per gallon, that would amount to a $5000 savings.
I felt pretty good that the fuel savings had "offset" part of the cost of the conversion -- until Clifford made the unkind observation