I just ran across the receipt for the fuel filters that I bought and thought I might send along the numbers for others to use. I bought 4 (needed for each filter change) #3825 fuel filters at $24 each and the needed gaskets are actually (need 2 per change) listed as NAPA FILTER GAS #5635. They were less than $3 each, but took 3 weeks to arrive, so I ordered 4 more to keep for the future. I dont know what Caterpillar charges, but Napa is 10 minutes from home and the nearest Cat dealer is 1.5 hours away so the choice was easy. Maybe these numbers can help someone else. Cheers, Grant.
Napa has filter sales at least once a year, some stores twice a year. It seems the store decides when the sale is. It is a big enough discount to really add up on the fuel filters.