Regarding your Civic, and mine, Honda doesn't have a "severe service" schedule for oil changes. The Owners Manual references CVT fluid changes at 25k miles if you live in the mountains, and they also reference changing air filters (cabin and engine) at 15k miles. Nothing for the engine oil, though. That said, I'm doing mine at 6 months, because almost all my driving is short trip, and my 1.5T does gas dilute the oil.I don’t consider my driving severe service because I do mostly highway and no short trips. But if I fell into the severe category the earliest I could see myself changing the oil would be 5000 miles.