If you pay $22 for 5 gallons, then it will cost you about 22 cents every 100 miles, or about a dollar for every tank of fuel you burn. Not enough to get excited about. Of course, you don't add any except during oil changes, so buy it by the 2.5 gallon jug and pour it in yourself every 5,000 miles or so.
I don't know the oil capacity of the new Ford diesel, but my old '99.5 PowerStroke requires 15 quarts of oil for an oil and filter change.
My Sierra Blanca in the sig pic was a great pickup for 11.5 years. I sold it a coupla years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream.