They can't be too bad. On my work truck I usually take it to the girls @ huffy lube (jiffy) and get the oil taken care of. Company pays so thats their deal.....
Oil is 5w20, with their filter. Use typically sees 80% highway, 10% stop-go, 10% extremely hard driving (0-80mph as fast as it can go to merge back into traffic)
All the above plus 12+ hours per day of run time, and the majority is sitting idle.
It still runs. Every 3k is the oil, company requested eveyr 5k until I showed them an oil analysis that said the oil should have been changed 3000 miles ago..lol That suggests every 2k changes which would be every 3 weeks.