We have a 2000 Saturn SL2 (120,000 miles). Last night we drove to L.A. and back (from San Diego) , so about 250 miles round trip. For the last 45 miles or so we had the radio on quite loud. At some point in that 30-45 miles the engine developed a very loud knocking noise - like rocks being spun in a tumbler - which we noticed when we got off the free-way and turned down the radio. This noise did not effect the way the car handled as I did not notice anything when the radio was up. We have been listening to a lot of sounds and I am concerned it could be a Rod Knock - it sounds a lot like this (http://www.youtube.com/watch?NR=1&v=Em4ZW3ZDIzA
) from inside the car, outside it was more of a constant pinging/thunking noise - less gravel sound.
So my quandary is this, our mechanic is not open Sundays so I cannot ask him, but when we take it to him tomorrow, do we drive it or tow it? If the rod is starting to go I do not want to inadvertently do more damage by driving it. The mechanic is 8-10 miles away. We can get their either on the freeway or through surface streets.