It has been 10,000 miles since my previous analysis. My trusty Honda Accord now has 174,000 miles. The duty cycle for this interval is different from the previous due to my move to an urban area last year. During this test interval my commute was 3 miles, and the interval period included wintertime where the car barely reached operating temp. I have since moved back to a move rural area and have a 22 mile highway commute, seen at the tail end of this interval. I suspect the hard city driving, short trips, and 3 mile city commute were much harder on this oil. I know that mileage dropped considerably during this time, and it is now much higher. Here is the analysis from Blackstone: http://isomerica.net/~dpn/D80660.pdf While the recommendation was for a shorter 3-4k mile change interval, I will probably stick to a 5000 mile interval based on the fact that my commute is now largely highway miles and the car always reaches operating temperature.