Made the switch about two weeks ago to Rotella Syn. Had run Delo 400 the last 60K miles. Now its leaking, Drips from the weap hole in the flywheel cover.
Checked the top end, no puddels Think its the rear main seal.
At 90K now the question is did the syn Rotella take out the seal? or do you think I have a larger problem???
No other leaks cept the Turbo base O ring about 25K ago.
Have read about syn causing leaks but thought I would be O.K.
Guess not........

 

Just make SURE you don't have a leak further up. I thought my rear main was leaking when I first got my truck, but it was just the CAC tubes under the spider (this was before the CCV mod, obviously).

 

Yeah, rear main would be really rare. I dont remember hearing anybody here having one go. Check the HP oil plugs on the back of the heads. They have o rings on there that sometimes leak. Have you done the CCV mod? If so, something may be restricting the vent line and causing the pressure to push oil out one of the seals.

 

your seals are used to your old oil and now that you switched it has to adapt the properties of the new oil it will leak for a little bit but should clear up. any time you switch oils types after being used for that long to a different brand will cause this.

 

Not to , but that is pretty much a myth with today's syns. Lots of guys (including me) have switched back & forth with no problems. I would bet money that if you switch back, the leak is still there.

My suggestion would be to clean the motor really well with Simple Green or something similar and trace the leak to the source. The way the back of the motor is, oil runs down and you'd swear it's coming from the rear main (like I thought as well), but mine came from above.

 

Just as Joe said above. It's not the change to synthetic oil. Anytime these engines have a leak in the engine valley up top it drains down the back and makes you think it is a rear main seal going. I was in your situation about a year ago. Turned out to be an o-ring on the HPOP under the fuel bowl. Oil just builds up in the valley then drains down the back. Most likely culprits are the tubo pedestal, oilf from the intake boots (if you do not have the CCV mod), oil line up in the valley.


Just as suggested. When the engine is cool - wash it down with some simple green and clean her up real good. Then you'll be able to see where the oil is coming from. Grab a good flashlight and look in the valley & turbo pedestal area.

edit: like asked above. HAve you done the CCV mod? If you have and it is clogged/restricted then you can have a seal problem

 

Here's one more thing to think about -- since the Rotella acts as a 5W oil when cold, it flows better inside the engine. But it will also flow better when cold OUTSIDE the engine, so a minor leak may *appear* worse with syn. Something to consider...

 

Bingo! If there's a small leak up top, it may not have been thin enough oil to let it run down the back of the block before it was heated up and baked on. The thinner oil might make it all the way down and out of the weep hole. Also, if there is a very minor leak, the thinner oil will have an easier time running out of the leaking spot.

 

Just for the sake of reinforcing advice based on fact, I agree wholeheartedly with what Joe, White Buffalo, and Jeremy have shared. I've switched a number of vehicles over to syn at high mileage points in the past twenty years, and have never had one develop a leak that was a result of the synthetic oil. The potenial Joe suggests due to the new oil's lower viscosity is the only potential "oil-change-related" leak that I can think of.

 

Had to work today dark now, but I will clean it up and see what i can see. Also have not done the CCV mod....More to come.....

 

I get the award for biggest dumb-a$$ of the week.
Did the SSHPX the same day I changed the oil (SO you can tell where this is going) checked the fittings and one was freakin loose. Tightened it up, Douched it off with the simpel green then water, fired it up, road test about an hour and dry as a bone!!! Thanks to all for the direction.....

 

At least you had a confirmation of where it was coming from and not searching for some mysterious oil leak - and it was an easy fix.

 

Don't worrry man. I won that award a few weeks back! Bottom line is - you found it & fixed it. Another plus for the FTE website

 

they should put a note at the top of the instruction page for the HPX that you are going to leak oil cause you will forget to tighten a fitting.... I guess even at the top I might not have read it, I wonder, can you take a picture of that, I LIKE Pictures....me caveman...

 

When I switched to Schafer's 15/40 syn blend from dino Rotella 15/40 I also developed an oil drip at the rear main. Switched back to dino Rotella 15/40 no leak.