Hi the trade off was for the escalating emissions targets, the loose engines as termed were produced as a looser fitting piston does not create as much friction as the conventional tight bore, less friction creates less emissions as it reduces the heat inside the bores thus cutting back on C02, every engineering principle for engines is that they run better when very hot but this has the side effect of raising emissions, Ford almost got round it with the CVH lean burn engine this ran hot but because of the lesser fuel charge it produced less emissions but unfortunately the oil technology at the time let it down.
All modern petrol engines burn a little oil its part of the price we pay for driving new off the forecourt and thrashing it a couple of days later which further down the food chain won't help the second hand buyer.
Steve.