I just went 9 months and only put on 2000 miles. I was down to 20% on the OLM. Since mileage wasn't a factor here I am convinced it uses Time and or Mileage
It uses running time per start, accrued mileage, actual time in days, ambient temperature at each start cycle, called a 'algorithm' among a few other parameters that I don't recall.
This 3-year old thread got revived from the dead due to a discussion in another thread about OLM. I think this document is a pretty definitive statement about how the OLM works in current (2010-2017) GM cars. The other documents (cobaltnitra.com and Edmunds.com) are either laughably generic, or describes GM's actions around 2000.
Of course, other manufacturer are free to use their own system, but since this is a forum focused on the Cruze.
'89 Corsica LT Hatchback 2.8L/Auto
'67 Chevy II, 250 ci/auto