You probably spilled some outside the engine so its burning it off.Synthetic is a betterhigher quality petroleum oil that gives u better protection over conventional oil.Your car will run cooler thus u dont have to worry if u pass your 3000 miles recommended oil change.It Shouldn`t HARM you car in anywaybut synthetic was not recommended during the break-in stage when u first bought your car to let the bearings and rings seated right.Since your car has 17K miles i dont see that was a problem. BTWwhat grade oil did you use? 15-50 could give u a little sluggishness to your ride. Try use a lower grade next time.