Ford issued a Technical Service Bulletin recommending 5W20 oil for the following vehicles. Your post doesn't state the year or model of your vehicle. If it is on the list below, then the current Ford recommendation is 5W20 oil:
Engine Oil - Oil Recommendations/Applications
ENGINE - ENGINE OIL - RECOMMENDED
APPLICATIONS FOR SAE 5W-20 AND SAE 5W-30
MOTOR OILS - GASOLINE AND FLEXIBLE FUEL
1992-2002 CROWN VICTORIA
1993-2002 ESCORT, MUSTANG, TAURUS
1998-2002 ESCORT ZX2
1993-2002 E SERIES, F-150, RANGER
1997-1999 F-250 LD
1999-2002 SUPER DUTY F SERIES, SUPER DUTY F-53 STRIPPED CHAS.
1991-2002 TOWN CAR
1993-1998 MARK VIII
1992-2002 GRAND MARQUIS
This article is being republished in its entirety to update the vehicle models, engines and years affected.
NOTE PLEASE REFER TO THE VEHICLE APPLICATION LIST LATER IN THIS TSB FOR A COMPLETE LIST OF VEHICLES AFFECTED BY THIS TSB.
Ford Motor Company now recommends SAE 5W-20 viscosity grade for servicing most gasoline and flexible fueled vehicles.
All 2001 and 2002 vehicles where SAE 5W-20 is specified should be serviced at the recommended oil change intervals using SAE 5W-20. This oil is an improved formulation to improve fuel economy.
Testing has validated this viscosity grade can be used in many previous model year vehicles. It is recommended ALL vehicles on the following Vehicle Application Listing be service with SAE 5W-20.
All 2001-2002 vehicles other than those listed in the "Exception 2001 Vehicles" or "Exception 2002 Vehicles" chart are being filled with SAE 5W-20 motor oil at the factory and should also be serviced with SAE 5W-20 oil.
1997 Mercury Grand Marquis