Okay guys here it is.

I don't know why but I feel this cumpulsion I top off my tank every 3-4 days, I don't like it going under 3/4ths tank, but it seems that If I just drive my car until the trusty reserve light comes on that the gas gauge moves twards empty slower! I know I'm crazy and am wasting everyones time, but I'm curious, do you get better gas mileage by letting her run her course, or just by topping it off over and over. Or is it the exact same? Its a 1995 e320.


Thanks for the advice,
Jay

Don't know where you live but its never a bad idea to keep it full (less moisture) in tank. but not to big of deal in most climants. The milage will be the same except with 1/2 a tank your car is carying 1/2 the fuel load.

Not much to gain from it so I would keep up your habit.

I always try to keep my tank half full (no more, no less) unless I'm going on long trips. Car is lighter, saves a bit of gas. I have no idea how big of an impact this makes, but every few penny saved helps.

The gas gauge needle may indeed move at different 'speeds' because of the shape of the tank. The sending unit is linear, it travels up and down, but the resistance may not be exactly linear. The tank has a shape, and its volume may vary by height. Small variations, but they exist. Also, on my car, full to the brim barely touches the Full mark, so it's on the way down right of the bat.
Your first gallon should take you as many miles as your last, it's just how much you worry about them!

The only difference in mileage would be that you're lugging around a few more pounds of fuel. The engine has no way of knowing how much fuel is in the tank, and does not care as long as it's getting a fuel supply.

Best Regards,
Jim

As the other have said, there is absolutely no difference in MPG or performance going with a full, half or empty gas tank, except for the unmeasurable difference due to weight.
With my car, when the "low fuel" light comes on., I still have about 110km (70mi) autonomy (yes, I have tested it).
I personally prefer to stop at the gas station for a full fill-up than stopping for a 5-6 gals. top off when the tanks falls below the 3/4 mark.