Mine uses about 3/4 of a quart of oil between fill ups (about 320 to 350 miles). It seems excess compared to other VX's, but that's the way it's always been so as long as I stay on top of it I'm not too worried.
As for your check engine light it could be a few things. The easiest thing to check first is if your gas cap is on tight enough. When you crank it down let it click a few times to make sure it's seated well. If not, that could throw a CEL. The other thing that I have noticed out here in Colorado is that I will get a CEL sometimes if I do big elevation gains or losses. I don't think the computer likes the different oxygen readings that it gets so it throws a tantrum and turns the CEL on. Could be that easy, but go to AutoZone and have them read the code for you.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless