I'm confused on how frequently to use this product. On youtube video, Liqui Molly seemed to indicate not using it every oil change, yet they also said it was designed for european oil changes with longer durations (up to 30k KM). So if I'm using FCP recommendation of an oil change every 7.5k miles, how many oil changes would I wait before using the product again?
Correct, this product does not need to be used on every oil change. It has an effective service life of up to 30,000 miles (50,000 km). The frequency of oil changes is irrelevant, mileage is the primary factor as to when you would use this product again. If you prefer to change your oil more regularly, say every 5,000 miles, you would want to use this product again on the 5th or 6th oil change. If you prefer an extended oil change interval, say every 7500 miles, you would use this product again on the 4th oil change. General guidelines are 30,000 miles ÷ oil change mileage interval = oil change count between treatment.