Looking for some advice or reference source. Am I running my Detroits too slow? I have twin 1972 Dteroit Diesel 8V71 turbos, 435 HP each. (In a 48ft Hatteras Yachtfisherman) .I usually cruise at about 1550 or 1600 RPM for several reasons: much better fuel enonomy, much less salt water bow spray, less wear and tear (I think). 11kts to 12kts suits me fine. Both engines are in good operating condition. These, like all 71 series Detroits are rated at 2300 RPM. Periodically I speed up to 1800 or 1900 RPM to "clean out" the engines at the advice of my mechanic. Rarely is there slight smoke initially, but if so, it clears within a minute. I estimate my fuel consumption per mile is over 20% better at the slower speed, roughly .7 mpg vs .55 mpg at 1900 My mechanic claims that at this "slow speed" my turbos are not really working and unused fuel is likely to dirty the turbos & engine. He says the turbos don't kick in until over 1800 and he'd like me to run at 1900 normally. (Of course, I'm paying the fuel bill, not him.) Also, I have installed RACOR CCV's, which is the negative crankcase pressure filter system equivalent of Walker Air Seps. So my "blow-by" from the crankcase, if any, is filtered and the oil separated and returned to the engine pan. (Oil blow-by, I know, can dirty turbo fans.) So any crankcase residue is minimized. Verdict? thank you, Rob Brueckner