Assuming it has the Lycoming IO-360 rated at 200 hp, I would go with 10 gph. This is what most pilots use for the purpose of flight planning But, as you know, the exact gph will vary due to altitude and with each engine. To get an exact number, check the fuel flow gauge while at altitude during your checkride prep flight, and then you'll have an exact gph to give the DPE if he asks. If your Arrow doesn't have a fuel flow gauge, then use 10 gph. If your DPE does asks, tell him your using 10 gph for the purpose of planning. If he questions it, tell him that your erroring on the side of caution by using a slightly higher number than what you normally get because the worst thing that would happen is you arrive at your destination with extra fuel. And remember, don't talk yourself into a corner by bringing it up without him asking you. Answer questions with the minimum amount of words as you can and sound confident. DPEs are more likely to keep the oral portion short if you sound like you know what your talking about.
