Smart 451 why change oil a lot faster in winter season. Idle contamination .

So check it out 2000 mile oil change but wife drove it to work 10 mile and 10 back and let it idle a lot. So is fucked! Look at the oil at just 2000 miles. Need to change it .
Is not the miles. If she drove 2000 miles on highway one trip that oil would still be good.