Q: Is it okay to use 5w-20 in my 2004 buick lesabre

You can use 0W-30, 5W-30, and 10W-30. You cannot use 5W-20 oil in ANY operating conditions in this vehicle as the viscosity will be too low once the engine is warmed up. Page 5-15 of the LeSabre Owner’s Manual contains a discussion of engine oil requirements and allowed viscosities. The allowed use of 0W-30 in the LeSabre, and other vehicles, has developed in more recent years (since publication of the Owner’s Manual that I referred you to) and although 0W-30 is not referred to in the manual, the major oil manufacturers do recommend that viscosity. It is great for cold weather starting. Overall, you can use the 5W-30. Absolutely do not use 20 weight oil (5W-20, etc.) due to the potential for engine damage. If you desire that this maintenance be performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine oil/filter change and the responding mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.