Oil Change interval 3000 miles OK? how bout over 6000?

You should change it every 3000-5000, use a quality filter (Mann or OEM Volvo). Change frequency depends on how hard it's driven, how dusty the environment is, and how many miles you drive, after time the oil accumulates corrosive debris and should be changed at least every 6 months even if you drive very little.

I would say every 3000-4000 miles or six month, which ever comes first. For me, six months always comes first. I change the washer after 3-4 oil changes. BTW: I use Castrol 20W50 during the summer (hot) months and 10W30 during the winter. I have a B21 Turbo.

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