The OP Mentions Fleet and he should have just used - As Cheap as possible. Sorry to offend anybody here but maintaining fleets of vehicles costs money.
Even using the Amsoil argument of negating a routine oil change to save money by utilizing a stronger oil doesnt make alot of sense to many fleet managers who track time in leu miles. Its easier to just change the oil more often then determine which vehicle out of 100 is due for its X,XXX mile oil change.
If the OP is looking to use HPL (a fine oil) in a demanding scenario, use it in a vehicle that sees track use, tows heavy loads or something that is going to be demanding. Not with the intent of pushing the OCI further, that just deosnt make as much sense in a fleet application or a way to prove or disprove an oil.
I just dont see the argument. My vehicles (construction transport vans mostly) get an oil change every 6 months with whatever bulk oil we buy. Typically 10w-30. Is it great, no. But the bodies and interiors fall apart much more often than internal engine components. Cost wise, fleet vehicle oil change is $20-$30 , so $60 a year. A HPL oil change once a year is more than that. In the instance where contamination or damage does exist, the oil is getting changed negating any savings.
Just one guys opinion.
EDIT: *Hope this isn't seen as bickering. I view this as an unfortunate and unclear comment by Moderators*