On Alfa number 15
AO Platinum Member
Join Date: Dec 2005
Location: United Kingdom
Re: How often do you change your oil?
If the engine is not getting up to temperature then I would personally class it as a short drive. 15 miles is fairly long as it should be up to temp after about 3 miles if your thermostat is ok.
Doing lots of short drives where the engine doesn't get to temperature cause unburned fuel, condensation and other contaminantes to build up in the oil. A longer run will make these evaporate out of the oil to a large degree.