Just a dumb question.

My 1991 250TD seems to foul it's fuel filters pretty quickly. It's my third vehicle, gets driven at least monthly, drives wonderful right after i've changed the fuel filters, but it seems like i'm having to change the fuel filters very frequently. I can tell when I need to change them because it's down on power, struggles to rev smoothly, and idles a bit rough (for a 5 cylinder naturally aspirated diesel.)

I keep inline and primary filters in the vehicle and am down to being to change both in 10 minutes. even with a hot engine. I order them in sets of 5.

Is there something I could/ should be doing? I'd like to not have to change the fuel filters more frequently that the oil changes.

A friend has a Nissan Caravan Silk Road diesel, and he mentioned a water separator was among the things he ordered. Could that be one of the issues? Water in the diesel? I only fill up at Buc- ees and sell a ton of fuel, so i know it's fresh fuel going into the vehicle.

Thank you for your thoughts.