well before you go and do that you need to take in consideration... does it smoke? does it leak oil already, or does it burn oil... ususally if any of this occurs, it would be well suited for a thicker oil than 10w30... 10w30 is more for a newer motor that doesnt smoke or burn oil or have excessive wear. 10w40 is more for the car that is older but does not smoke or have excessive wear and 20w50 would be for the cars that are older and beat on (floor boarding it alot or racing)... putting a synthetic blend in a car that already leaks oil or burns oil will make the problem worse, its a proven fact. The best thing to do is, you know your car better than anyone, based on this information, what oil matches the use of your car. good luck - Jason