I purchased a used 2007 mazda 5 about 6 months ago. Up until the past week I'd had no issues. I noticed at first the battery was draining and then the last two days it had needed a jump. Yesterday, on my way to work, it started to tick like it was low on oil (oil change was scheduled for today), just before getting to work it shut off and acted like the battery was dead (sluggish turn over etc). I got a jump, it started just fine, but sounded terrible. Knocking and clanging in the engine compartment and showed no oil on the stick. I've never noticed a leak, I check the oil regularly (weekly) and its never been low. Having no other choice I dropped oil into it to show good on the stick and drove home (10ish miles). It will start and run now, but the tapping/clanking noise is ever present if the car is running now. I'm not familiar with the engines in these cars, so I'm looking for a place to start or an idea of what I may be facing.