Right now I'm maintaining a 1993 Honda Accord 2.2 w/275,000km and a 1995 Honda Civic 1.6 w/245,000km. Both are getting Napa Gold filters with Pennzoil YB 10w30. The Civic is getting 6mo/8,000km changes. Usually needs 2 liters of top up in between. The Accord is getting 12mo/8000km changes. I last changed it in January and am just approaching 5000km on the fill. It also gets topped up, so far about 2.5 liters since then. Now, I might be leaving my job, which gives me easy access to oil changes whenever I want. Can I use Amsoil in these engines and go the full 15,000-20,000 between changes? As long as I keep it topped up with Amsoil it's fine? Invest in Amsoil oil filters right? Or else I'd have to change conventional filters between drains? My Accord doesnt get much mileage on it. Is the maximum 12 months regardless of mileage, or can I top it up and go the distance? Remember, both burn oil and need top ups occasionally.