Cat's design lifetime on these engines is stated to be 10,000 to 15,000 hours. So to be conservative, at 30 M.P.H. And 10k hours, = 300,000 miles. At 40 M.P.H and 15,000 hours = 600,000 miles. I have heard of the engine going 500,000 mi. in non-military applications. For comparison a...