I had a oil change on my E430 at 70150 miles and now with 73750 miles on the car, the service light comes on. I thought the E430 would run more than 3600 miles between services, I've read the car should run some 10,000 to 12,000 miles between services especially in California. I noticed on the last service the mechanic put in 9 quarts of Castrol 20/50 oil . I don't misuse the car, just normal city and highway driving, put 3600 miles in the past 6 months.
Is this normal? Looking for your expert opinions and suggestions.
Thanks, John