What is the oil filter number for a 1989 F 350 XL 7.3 diesel engine?

There isn't a single definitive oil filter number for a 1989 Ford F-350 XL with a 7.3L diesel. The correct filter depends on what filter brand was used originally or what the owner has chosen to use subsequently. Different manufacturers use different part numbers, even if the filters are functionally equivalent.

To find the correct oil filter, you need to either:

* Check your owner's manual: This is the best source, as it will specify the manufacturer's recommended filter.

* Check the filter itself: If you have an old filter, the part number will be printed on it.

* Use a parts store's online lookup tool: Provide the year, make, model, and engine size to get a list of compatible filters from various brands (like Napa, Wix, Fram, Motorcraft etc.). Be sure to double-check compatibility.

* Consult a Ford parts dealer: They can look up the correct part number based on your truck's VIN.

Without more information, I cannot give you a specific oil filter number.