At moderate acceleration, the engine seems to have a faint, low-pitched thumping sound, not a smooth V-6 pitch; is this a normal CL noise? I put in high-test to be sure it wasn't knocking, and it didn't change. Time to check CV joints for lube? Car has 49K miles. Don't hear it any other time and car runs great otherwise.

PS- About 500 miles left on warranty.