First of all, why would you trade your XB with less than 100K? My grandson has a 2009XB with 228K and it is still going strong. NEVER USE ANY OIL IN YOUR XB OTHER THAN 0/20 OR 5/20! 10W30 has a viscosity that is to thick to flow in your XB. You run the risk of causing the engine to fail. If you are worried about gas mileage, control your right foot and drive less aggressively. You may put 2 t0 4 oz. of Marvel Mystery oil in your gas fill up and it could help a little in your mileage.