It depends on what Lumina you're driving... the sedan or the minivan. The sedan STD had a 160 horse, 3.1L V6 engine that was good for about 2000 pounds. The sedan LS had a 210 horse, 3.4L V6 that took you up to 2400 pounds. The APV/minivan came stock with the 3.1L V6 but had a towing capacity of about 2200 pounds due to the rear end setup. If you went for the engine upgrade a 165 horse 3.8L V6 tied to a 4 speed overdrive automatic transmission then you were bumped up to 3000 pounds of towing capacity. Only a 3 speed transmission was available for the 3.1L engine. A good place to look for this info is in the owners manual.
Holy crap the poster above me really knows what he's talking about. That was a lot of precise information on Luminas. I was just going to say check your owners manual if you have one. And what are you going to be towing with a Lumina? Well good luck. Hopefully you find the info your looking for.