I was wondering what cause injectors to leak fuel into the oil. I had all 8 injectors replaced , a few days later i checked my oil and had fuel in it. I took it back and they said that one of the injector return rates where really high. So they replaced all 4 on the passengers side. I picked the truck up yesterday and today checked the oil and it was high again on the dip stick. I don't know if this matters or not, but the dealer changed the oil for me the first time and put a quart to many in. If you can Please list what cause injectors to fail or leak fuel. thanks

Return lines at the injectors are probably loose.

cracked line a possibilty too

Bad/incorrectly installed sleeve.

Thanks for the info I'm taking it back in tomorrow we will see what they have to say