Yes, air is always bad in fuel system and also lots of dirt. However there are fuel filters to protect the system from dirt. The engine sucks its fuel aways from the bottom of the tank. So thats no excuse to dont drive the tank to "empty". Still the air i a problem so if you drive your tank to empty drive smoothly the last 40 miles etc...
I believe I wil hit 900 after three week when I go again to my homeplace. I have got always the best mileage on that trip, because the full tank is trip consumption and speed limits are lower than on my regular week route
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