So I know the latter symptoms point toward the plenum gasket failing, but haven't seen gas in oil reported. Changed my oil today and it reaked of gas. Pulled the air cleaner and noticed residue, fairly fresh looking. And I haven't owned a 5.9 gasser in years, but the power seems a bit down, and I've only gotten about 124 miles on 5/8 tank of fuel, which seems a bit low. The truck has 170k miles, new 4.10s and 285s, plugs, cap, rotor, air filter, etc

 

Plenum went bad. Most likely took the front o2 with it. Thus, dumping to much fuel into the cylinders. Hence your poor gas mileage. (Recently had the same issue with the o2) The fuel smell in the oil? Maybe try a compression check to make sure your rings are sealed and the excess fuel isn't dumping down a bad ring instead of sucking oil up? Maybe try changing your timing chain as well if it wasn't done previously as I hear they stretch good by 150k. I'm doing mine real soon...

 

If the engine is running excessively rich, you WILL end up with gas in the oil. Also tends to wash down the cylinder walls, so rings don't seal, and cylinders wear FAST.... Need to address that before you need to do a complete rebuild. (if you don't already.....)

 

that is no bueno. Current plan of action is to test compression ASAP, and if I still have ok compression get the plenum fixed. If the cylinders don't have good compression, and it's looking like a rebuild, it's time to start ordering the parts for a 4bt swap. Cause if I need to pull this gasser out, she's not going back in

 

Compression may show low numbers, yet the cylinders are still good, simply because they have been washed down by all the gas...... Disconnect the front O2 sensor, drive it for a few days, (after an oil change) Then test your compression.

 

Just did the oil change today, so I will disconnect the sensor and then wait to do the test. I'm assuming I will just run lean?

 

No, it will run just a tad rich, not insanely rich, like you seem to have now.

 

Well still leaner than now hopefully, lol. Well there's my plan, and we will see what it yields. Looks like I should start doing the research on transmission and t-case options for a 4bt swap

 

There is a thread around here somewhere, where a member did the 4bt swap... might wanna dig it up.

 

I've actually been reading about them a bunch already, in plan to do one at a much later date. But if that date needs to be moved up, that's all there is to it lol. This will be my 5th 2nd gen ram, the others were all 12v and 12v trucks and loved them to death. But the 6bt is just a bit much for these 1/2 frames and the 4bt will be a torquey little motor and provide great mpg