I thought its condition, which is how it also gives you oil level at ign on - the automotive oil sensors by conti-temic, delphi etc have this functionality built in. The service indicator uses mileage only countdown but thats independent of the oil and the oil sensor reset is in the engine ecu function on fiat ecuscan, which is how i arrived at my conclusion. But I don't know anyone at FPT so can't confirm.
In any case, depite all the claims about how good synthetic oil is these days, i'd always get at least an annual change. As the saying goes, oil is cheaper than a new engine.