Oil consumption is not AT ALL related to fuel consumed. Oil and fuel do not mix, and there is no "ratio" program.
Oil delivery is based on engine RPM and load, combined with throttle position. One other variable is how fast the throttle is advanced (a sudden snap of the throttle delivers a "50-shot" oil pump count... anticipating WOT will be the target).
So it's entirely possible to have one guy that runs a fair amount of low-to-mid RPM's, and operates conservatively (and another that is Mr. Happy Foot and like to make mid or high RPM runs) use CONSIDERABLY different amounts of oil.
Especially the "Mr. Happy Foot" variable.