I've heard the stories about acetone helping fuel mileage. I'd be afraid it might doa number on thes internal seals of the IP. 23mpg is pretty good, but its not unheard of for a Cummins. They are smaller displacement, have 2 fewer cylinders, and in stock trim, not turning out probably quite the ponies of the IDI especially with a turbo. On the whole, they are a slightly nore efficient engine to start off with.