Thanks to all ... just did the job and I can't imagine anything went wrong. The old filter was dirt-caked and there were a couple LEAVES outside it in the housing! I cleaned out the housing carefully, put the new filter in, screwed on the top and we'll see how it goes when i drive it to work tonight. Is it something where one should re-open and check after a while to make sure it's doing its job, or is it one of those if-anything-is-wrong-you'll-KNOW situations?

Wow, PS fluid/filter change and air filter change in one week ... aren't I special? (not sure why I chose that emoticon ... I did not loose an eye during either maintenence job. But I did lose part of a knuckle during an oil change)

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

I would just leave the filter alone, opening it again will just increase the risk of getting dirt in the intake.

BTW, I had to look up "emoticon."