The main cause of why your gas is getting into the engine oil is that your fuel mixture is too rich. If your fuel mixture is too rich, the combustion chamber won't ignite all of the fuel and this will cause the fuel to run throughthe piston rings down into the oil pan. It is not easy for your car to maintain this ratio. When it fails, and there is too much fuel getting in the engine for combustion, we say your car is running rich. It means you arespending lots of fuel while driving. To prevent further loss of fuel, car manufacturerss use sensors to control the fuel-air mixture. Your car should not be having problems like this that new. I would also check what warrenties are on the car and if there are any recalls take it in. Some ways to fix a rich air fuel mixture if you find this is the case is to clean the Mass Air Flow sensor, check the flap of the air duct, check if the vacuum line is loose or has a leak, replace the O2 sensor, or replacing the spark plugs. 

I would check the STFT and LTFT, clean the MAF sensor and change the engine air filter and see if the MPG is imporved.