20W/20 will kill the Endura!
Bascially you will need oil which has cold end protection of 10W or below, and hot end protection of 30 or above...
So if your car is made before May 1999, 10W/40
If your car is made after May 1999, 5W/30
Don't put any 20W/20 into the engine!
Hope these helps
Phil