Depends on how much oil I keep in the crankcase, more so in my 500 hour TTSN IO-360 than my old 1,200 hour TSIO-360. For local and regional flights, the sweet spot for fill in my IO-360 is 4.5 quarts. More than that ends up on the belly in an hour. With a 4.5 quart fill, I estimate my burn to be...