R134....But to be sure, lift the hood and there should be a sticker telling you what type of refrigerant to use.
r134
R134a
R134
R134a
R-134A
134A
R134a
A 1999 Chevy Lumina 3.1 uses standard R-134a refrigerant. It has been used nearly exclusive in automobiles since R-12 was phased out in 1995.
134a
R-134a
R134A
r-134