Hello, I've had this long-term problem with my 2014 5.3 L Silverado. I've been getting gas in the oil since I bought it one and a half years ago. I took it to a local shop and they assured me it had to be the high pressure fuel pump which they then changed. Still gas getting into the oil. I returned and they replaced my injectors, ones that I had bought on eBay which were OEM and brand new. They did this service for free which I was impressed by. Still gas in the oil. They replaced the high pressure fuel pump under warranty a second time and I was still getting gas in the oil. At that time I mentioned to them this truck does not seem to be running at the correct temperature as my gauge never read over about 175°. I purchased a OBD 2 reader that monitors coolant temp. Took the car on a 40 mile drive and it never exceeded 132° Fahrenheit while the gauge was reading at about 170. I replaced the thermostat and immediately the engine started running at 200° Plus on the OBD Monitor and the dash gauge which is normal in my mind. I'm thinking now that this whole fuel in the oil problem was related to a cold running, Rich engine although I never received a code for low engine temperature. I haven't driven the truck enough now to know if it's still taking on gas in the oil but I'm pretty confident this might have solved the problem. What does everyone hear think? Thanks for your thoughts