On 16 Jul 2016 11:35:26 GMT, David wrote:

If it is a newer style barrel shaped one then there is no correct answer
because the volume per inch varies with the profile - in the middle the
tank will be at its widest so you will get most oil for your inch.

Top and bottom will be narrower so you will get less oil per inch.

Except that the tanks aren't true barrels. They alternate round cross
sections with rectangular. With the both having the same width at the
center. So although some of the tank does get narrower the rest is
staying the same.

On our tank this means that the amount of oil per unit depth is
pretty close to, if not actually, linear.

--
Cheers
Dave.