I won't get into the economics of diesel vs gas. However the 36' trawler we lived aboard and completed the Great Circle Route on is powered with a 100 HP Volvo diesel engine. Her engine is approaching 9000 hours and her keel has passed over 60,000 miles since we bought her in 1992 (she was 7 years old then and we don't know how many hours she was operated or distances she traveled in those 7 years). She still burns 1.3 GPH at 6.3 knots (7.2 MPH) getting 5.57 MPG. We and the present owners have replaced oil and filters and performed repairs on a number of small items attached to the engine, but the engine itself still runs as smooth and strong as it did when we bought her 12 years ago. I hear all the time about estimates of "rebuilding at 2000 hours", and even the manufacturer recommends overhaul at 10,000 hours on this engine. However, a mechanic once told me, "if it ain't broke, don't fix it!." I have a theory that diesel engines that are in boats that are used regularly (this boat has been a live aboard cruising boat for at least 12 years) will last much longer than typical boats that are used infrequently or laid up during the winter. Just one comment from a boat that has gone the equivalent of 10 times around the Great Circle Route in the last 12 years. Bob Skipper Bob Publications Http:\\SkipperBob.home.att.net