This job is not your average DIY job; and since the air filters have to be removed to access the fuel fillter, it's definitely a job to be done at the same time.

25K on my ML320CDI. Disassembly is major to remove and change the filters. (Why can't they make them as easy as the oil filter?!??!!) Neither the W164 nor the R320CDI Service DVD's provide complete instructions. It's a matter of removing this to get at that - some of which is intuitive and some of which is not. It'll take me 6-8 hrs before all is said and done. Next time it will probably be 2-3 hrs.

The air filters were so dirty that they were almost sealed over with trash. I'll bet my fuel economy and/or engine power improve with this maintenance.

My recommendation is to let your favorite trusted mechanic do it for you; and, no, I didn't take pictures.

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1973 280SE 4.5 (Sold)
1984 LWB 280GE (Sold)
2000 G500 NMLE - "Deep Throat"
2007 ML320 CDI (Sold)
2010 Porsche Cayenne S Transsyberia TipTronic (Sold)
2010 Audi Q7 3.0 TDI (Sold and Sorely Missed)
2014 ML350 BTC
2015 Audi Q7 3.0 TDI (On Order)