I was scanning for IAT today, and noticed that while my air temps stayed in the 140-150 deg. range my fuel temps got up to 160 deg F after the truck was subjected to a few stops and starts with it sitting in the sun.
I would have to think that you could dramatically increase your milage corresponding to the potential drop in fuel tempatures.
It just needs to get off the hot engine.

water probably rusted up your vent wire dropping fuel circulation in the pump, doesn't take much.

Where exactly i the vent wire?

under the top cover theres a small hole drilled through the housing which allows access to the vent wire which can be removed, replaced with a 1/8" allen, and a magnet would help too. when you remove it, you will notice its nothing but a small plug with a hole in it an a wire run through it. observe it for rust, spin the wire by hand to see if there are any rough spots and also look to see if the number is still visible on the top. I replace them every rebuild, its too cheap a part to try and salvage. I would reccommend going to a fuel shop and purchasing a 21662 (#2 vent wire) and replacing it. the lower the number, the higher the return fuel will be. a lower number will also allow the pump to purge air from the system much faster. from my experience, a #2 will put you right at top of spec for return oil flow (900-950cc/min @ 3400RPM @ 20cc delivery), if your pump has some serious mileage on it a #3 would probably be sufficient, as leakage from other sources like the advance piston will undoubtedly by higher than when the pump was rebuilt. Edited by: Texas Diesel Guy