Identification

• There is no mechanical reason for engine oil being in your fuel tank. The two areas -- the fuel tank and oil repository -- are not connected in any way. So you should not expect some sort of leakage to be present in your truck, or an obvious malfunction.
  
  

Best Bet

• Somehow, the oil was introduced into the gas tank inadvertently -- or perhaps purposefully by a prankster. One possibility is that the gas tank was filled from a container that housed two-cycle fuel, which contains oil in the mixture, rather than one that contained straight gasoline. Many homes have two-cycle containers around for lawnmowers, snow blowers, weed trimmers and other tools. Two-cycle fuel is also used in some motorcycles.
  
  

Solution

• As long as the oil in the tank is minimal, it should simply burn off with the gas. Contact a local mechanic familiar with your truck make and model to get the best advice. You may be able to use a siphon to empty the tank. Use a siphon pump to avoid dangerous inhalation or ingestion.