Not quite as simple as you explain it, this went on for some time, with lots of trials and testing done. The contamination of the paper air filter.....I recollect a modification being introduced, I said at the time, what idiot would design a breathing system feeding crankcase vapours to the suction side of a paper filter, it was bound to clog as it was mixed up with incoming dust.
As for dipstick levels, these were altered when rebuilding the engines, and measure ot the fraction of an inch......this amused me because once an engine is running, oil is splashed and pumped around, so unless the level was grossly too high, it would not be a problem. Another thing, vehicles, especially off road ones, work at all kinds of angles, so another reason why the oil level was a red herring.