Ok, I know for sure that a cruddy fuel level sender, loose connections at the sender or gauge, levelness of the ground that the car is sitting on, as well as physical damage to the tank can cause weird fuel readings. However, assume for a moment that none of those are issues.

How accurate is the fuel sender? What if the "empty" portion of the gauge counted? If you look at the spaces on the gauge, you have five (5) sections. A half-tank is actually on the full-side of half around 3/5ths, and a empty reading is not really the bottom.

Without draining my tank for fun and reading the Ohms with a tester as I add gallons of fuel to the tank, how sure can I be about the present fuel level based on the my gauge? Some makes of car hover at full for some time before dropping rapidly to a 1/4 tank. Other, usually newer cars have very consistent and correct fuel gauges. I'm not sure where these vintage cars fall, as I've had no good frame of reference so far... When swapping tanks, I did determine that the gauge reads slightly above true empty with one gallon.

I ask because, if you've been following my timing and fuel economy thread, you know I was suffering abysmal fuel economy - 10-13 mpg at best... It appears that my fuel was being lost mainly through a leaking float bowl seal on my rear SU HS6. Now that I've replaced those seals, my float needle valves, and all my fuel line clamps, as well as as my condenser and points, things have been looking up.

Since I filled up this week, my fuel gauge has dropped quite slowly. My gauge is presently sitting at the 1/2 mark, and I've put a little over 100 miles since my last fill-up. That's about 20 mpg, maybe slightly higher if I have really have burned 5 gallons. It is not wonderful, but it is certainly a huge improvement over the last couple months

If the 1/2 full mark is actually 3/5ths, then my economy is much better, more like 27 mpg...

So... what can you guys tell me about the accuracy of fuel gauge??