I work for a Komatsu dealer. When the computerized engines came out about two years ago, I was told in a class the truck would burn about 3% more fuel than the non computerized trucks. I believe this to be true. The older trucks run right next to the newer trucks day in and day out. If they were burning more fuel ,on the line of 40% more like you are saying, the operators would know and tell me about it. The operators know if a truck is 5% faster. They don't like changing LP tanks. They would be avoiding trucks with frequent tank changes.