This question has been bugging me for a while... I tried searching but surprisingly didn't find anything. I didn't see anything in unabomber's FAQ either...
Basically the question is: is there a point where one should switch from the factory recommended oil weight (in this case 5w30) to another weight due to high mileage?
I see mobil1 10w30 advertised for high mileage cars... I'm almost at 200,000 kms and have been using 5w30 forever... Is it just marketing (not sure why since the oil costs the same) or is there a legitimate technical reason to go to a different weight on high mileage engines?