The 633 is a great bargain if you can live with just a little less power in exchange for better MPG. They are wonderful commute cars whichever model you choose. The automatic is a weak point on these, but velvety smooth when new. Have a mechanic check on any car you are considering- this can save you big $$$ Mark S. '84 633 Can anyone educate me on this? What is the difference between the 635csi and 633csi? Also between 635csi and regular 635? (I assume those differences also apply to the the 633csi and 633) Thank you and please excuse my ignorance. I trying to buy one of thesse magnificent autos and want the best for my $$$$.