I was wondering if I should continue to use the recommended 5w-30 oil for this high mileage Civic? It is the single overhead cam engine, not the VTEC. It seems as if it has developed a piston slap when cold. It goes away when warmed up. I am running Penzoil Platinum 5w-30 right now. The car is driven most every day 20 miles to work and back on a 70MPH highway. I do OCI by the light which turns yellow at 4500 miles and then red at 5000. I usually change it between the red and yellow lights.