Oil/gas leak
 

When the car is running, Oil/ gas leaks from a loose bolt on the valve cover. If I tighten the bolt down will this fix the problem? Should I be order it's a mixture of gas and oil.

There are actually rubber seals on those bolts. Overtightening them will break them off, leading to worse problems. Simply replace the rubber seals and the leak stops. Also, it's most likely only oil leaking.

No there's gas too. Thanks for the info.