Had the oil changed this afternoon. I've always had it done at Wal-Mart (yeah I know, I know, but over several years have never had a problem). I always pick out my oil (castrol), give them a Toyota filter to put on and then watch. Tonight I didn't watch them very carefully. When I started it up it idled a little rough but no big deal. On my way home I noticed the oil pressure was slightly higher than usual. Stopped to fill up with gas and thought I would check the oil just to make sure it was ok. When I opened the hood the first thing that jumped out at me was a big hole in the top where the filler cap should be!! They forgot to put the cap back on. Looking around I found it sitting on the battery!!! It doesn't look like any spilled out and the level was ok. I had only driven about 5 miles and the rest of the drive home went ok. Needless to say, I'm going to be "speaking" with the manager in the morning. Should I worry about any ill effects?