You don’t need any additives in a properly functioning 7.3. And you’re not in a cold climate, so you don’t need to worry about an anti gelling additive.
If your injectors are showing signs of wear, archoil additive in the oil can help you along until you save up for new ones. Otherwise, change your oil and filter every 5k miles and fuel filter every 10k and you’ll never have an issue
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