I changed the oil and put new fuel filters on my 300D when I bought it last spring. I've put about 4000 miles on it now and it is time to change the oil. How often does one change the fuel filters, with the understanding that the car is running well and I am not showing symptoms of clogging?

thanks,

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Charlie

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)