Originally Posted by funola

On VO, the reserve light and fuel gauge reacts much slower than on diesel because of the viscoisty difference, even after drilling out the drain/fill hole in the sender to a bigger size. I may drill it out bigger to make it react faster. On mine, when the reserve light comes on, it stays on (this is on the highway, no sharp turns etc).

Just realized that when the light comes on, I probably will not be at a location where it is convenient to drain the tank.

Plan B:

On level ground, when tank is near reserve (light not on), slowly drain tank till reserve light comes on, then continue draining into another (empty) container and measure what comes out.