"I'm curious to know what RPM do you normally cruise at?"
It depends on the "mission"! If I'm just boring holes on a local flight at 2,500' msl or less (Florida), I really don't pay much attention to the tach. I pull her back to what "feels" right, usually around 2500 or so I guess, lean her out a little, and trim for level flight. I leave the ground with full tanks, and land with most of it still onboard! The only "numbers" I worry much about are max and min limits, to keep me out of trouble. I make note of indications for future reference, but anywhere in the middle generally keeps me satisfied, so I can sit back and enjoy the flight! I like to keep my head outside, and don't enjoy "pinning" the numbers when it's not necessary! Fuel consumption is calculated (a guess) according to time aloft, rarely over an hour and a half. I use the always inaccurate fuel guages only to reassure me that I don't have a massive leak!
Flying cross country is serious business, though, especially when you're stretching it! The numbers become paramount! I cross-check ground speed, range, and endurance constantly during the flight, to make sure I can make an alternate with plenty of reserve.
When planning a cross-country flight, I use the POH numbers for range and endurance less 20% to allow for takeoff, climb, and reserve, with range adjusted for predicted winds aloft.
At altitudes above 7,500 feet, even max throttle can't yield more than 73% power on our O-200's, so aggresive leaning is appropriate and needed. I true out at about 120 mph @ 5.5 gph when properly leaned (this can vary slightly from one 150 to another). Knocking 100 rpm off max gives me about 5.0 gph, and still around 115 mph true, increasing my range and endurance if needed. If I could stand seeing the IAS around 85 mph (about 100 mph TAS @ 7,500'), with the tach at 2400 rpm I could see less than 4.0 gph and well over a 500 mile range in no wind. It's all relative! Most pilots can't stand seeing IAS drop off, and pay the penalty in fuel bills!
"I had experienced higher than expected head winds which taught me to keep track of fuel in terms of time instead of miles."
I think most instructors need to stress this more than they do! Winds aloft won't affect your fuel flow, but can drastically affect time enroute and range. That's why fuel flow is measured in GPH (relative to time aloft ... get it?)
Hey Dave! I'm no expert! With higher than predicted headwinds, I once landed at my alternate and took over 23 gallons in my 150's STANDARD tanks, so I learned, too! I had just bought the unfamiliar plane, I wasn't leaning aggressively enough, and I didn't have a gps onboard for easy cross-checking. Licensed to learn!
