That's very common and if it's truly 'light surface rust' can be fixed very easily. (Hack?) In fact, a light polishing can improve things all the way around. As others said - a VERY fine abrasive of some sort with oil usually takes it right off. If you'd like to go further, get a fine emery cloth and a length of leather boot lace. Cut the cloth about the width of the lobe or journal, long enough to completely encircle the lobe/journal. Spray a bit of WD40 for lube, wrap the emery cloth around the lobe/journal, and completely encircle it with the boot lace. Alternating pulls on the end of the bootlace will move the emery cloth very evenly back and forth over the entire surface of the lobe/journal. A half hour's worth of time will reward you with highly polished lobes and journals. Don't go crazy - don't want to remove much material at all. Just nice and shiny.
Michael Yount - Charlotte, NC - 82 Volvo 242 - 6.2L; '15 Fit; '16 CrossTrek