At the 53z’s maximum velocity, her four engines consume about 142.3 gallons per hour, resulting in a range of 272 nautical miles. Dial the speed back to a relatively leisurely 37 knots (around 5,000 rpm) and fuel burn drops to 114 gph, while range pops up to 297 nm. Bring the yacht down to 31.6 knots (around 4,500 rpm) and fuel burn falls off to 90 gph, while range increases to 320 nm. That’s 0.4 nm per gallon, which is a pretty consistent number for this yacht between 2,500 rpm to 4,500 rpm. At the 53z’s top speed, efficiency drops a hair to 0.3 nmpg.