Yuck-- gotta read the label thoroughly before buying mayonnaise. I got Light Mayo last time-- yuck! Not only better for you (bleargh) but tastes like ass.
I always go for Olive Oil Mayo. Works for me. I think I bought Light Mayo once too...Of course the secret to mayo is to use very little or spread it thin...Well, here's an idea: Get a good mayo but mix in a little of the junk stuff (as you use it I mean), just to make it go further...