small amount of sludge

How often has the oil been changed? Sludge usually results from not changing oil enough. There are engine flushes that will fix this(that are basically composed of kerosene). I used a flush and some straight kerosene on a friends Hyundai that hadn't had the oil changed in 80k miles or so.....there was so much sludge couldn't even put oil in as the hole was plugged!

It's merely from not being warmed up fully and regularly. Take it out on the highway for at least 30 minutes at least once a week. Otherwise all the condensation doesn't get boiled out of the crankcase.

I have SL1 1994, like to once a year , use GUNK MOTOR FLUSH. This takes all the garbage out of my motor. Pour it in and run for 5 minutes. Flush out and change oil. This year I had to do it differently. I usualy use castrol syntec oil 10W30. This time I flushed it with gunk changed the oil replaced with cheap oil, had a good run with it and changed it again for fully synthetic again. It had been a year since my last oil change. Now the oil is sparkling and motor runs just fine again. Maybe this is all it needs, to be flush out real good then put whatever oil you usually use. Hope it helps

You sure you've got a Saturn and not a Toyota?

In any case, sound like the car needs to be driven out on the highway a LOT more. Short drives are bad for cars - they never really get up to temperature and don't burn the crud out of the crank case.