You do not mention your engine size.
However for a 3100 engine the GM manual specifies a SAE 5W-30 for best fuel economy and cold weather starting.
For a 3800 engine or a supercharged engine the manual specifies
SAE 10W30 for temps above 0F (-18C) and if it is going to be very cold
SAE 5W30 for temps below 60F (16C) and below only
Hope this helps.
"G"
Grand Prix is French for Big Prize and is a Formula One motor race. For example, the 2012 British Grand Prix
Motor bikes take part such as Ducatti.
880
For a Pontiac Grand Prix with a 3.8 L engine the factory recommends 5W-30, however during the winter months 10W-30 can be used.
I have a 2000 Pontiac Grand Am SE and it takes Dexcol, it's bright orange instead of green.
When you don't know try reading your dipstick, it normally tells you what type toput in you tranny.
134a
5w-30 is what I use in my 2000 grand marquis, in 2001 ford started saying 5w-20.
R134a
Dex-Cool
a Geo, Grand Prix, Gremlin
5W-30