I have n 06 chevy 1500 with a 6.0. I noticed my fuel mileage has went down a bit in the last 2 tanks, well I check my oil every so many miles and last time I checked it was 1500 miles ago and it was full. Today I checked it and it was 2 quarts or better over full. So I drained and checked it and sure enough it had over 8 quarts of oil came out it. I put a fuel pressure guage on it and it ran at about 55 to 57#'s and turned it off and it held pressure. It only lost a few lbs after about 10 minutes of it sitting. So I pulled the fuel rails to check injectors again, turned key on and off and injectors are dry no leakage at all. I figure all it can be is pressure regulator but how do u check to make sure?

 

Look some where else. it sounds as if your fuel system is working ok. A few pounds drop is fine after shut down. Does the engine get as hot as it should? a stuck thermostat will cause the same issues. What do you have for mods and tuning???

 

Truck has Zr1 cam, headers no cats, 160 thermostat, and has been dyno tuned locally. Truck made 387 to the tires. Truck was done back in July. Tuck runs about 180 degrees all the time.

 

Does the oil smell like fuel or sweet like coolant?

Actually, if it was coolant, the oil would have been milky when you drained it. I'm sure you would have noticed that. Does the truck have any starting issues?

 

No it smells like fuel and it starts normal, just dumping fuel in my oil.

 

PCV system?

 

How can I check to c if that is the problem?

 

has anything been done to it?

 

I put a breather on my oil cap but it has been like that. I just checked it today and it has gained almost a half quart of oil in 100 miles of driving. Oil smells like fuel bad.

 

What about the evap system? If something is wrong with one of its components, can it somehow siphon fuel into the motor?