This is my first time writing and have read every post concerning oil issues and idle concerns. I have a Lariat dually that was built on March 3. I ordered it because I bought a Lance truck camper with a slideout and also tow a boat. The truck handles the load perfectly and love the motor and trans. Not a single problem until the dealer did my first oil change and tire rotation at 5000mi. Other than finding loose lug nuts and not lining up my rear tires so I can access my inner valve stems, all's well.... I thought. After sitting an hour or so, I started it and it shook for about 5 seconds and puffed blue smoke and then instantly cleared up. No problems the next morning, but then same thing after sitting awhile. I took it back the following Mon to the dealer and raised cain about this and the lug nuts. They gave it back an hour later and claimed someone put the wrong weight oil in, not 15/40. Nice service no? Well it still does it but to a lessor degree. So after reading on this site, I ordered a case of the Chevron 5/40 syn. Will put that in and even though it's expensive, it may be worth it. I had a heck of a time finding ANY 5/40 oil! Syn. is all I found... and that had to be ordered through a Chevron distributor. Looking forward to trying it. Now, I also read somewhere that ford used a defective injector design and changed it in April. They had what they call a hot soak where raw fuel enters the motor through these bad injectors. Now my truck probably has these and the rough idle and smoke would sure be a symptom, but the darn thing has, and still does, run great. The oil change jacked me up. I know Ford knows about this but will not issue a recall. Is my motor a time bomb ready to go off 5 years and a day from now when the warranty is up? Going to the dealer is not an option so now what? Just run it? Lastly, anyone have a thump they feel in the drivetrain as they pull away after parking awhile? Been there since day one and I read it may be a lack of grease on the slip yoke. Should this be looked at? Sorry for the long post but I still love the truck and want it for a long, long time! Thanks, Neil Blanchard in Ventura, CA

 

I also have a thump but dont know what it is.. Though it was normal..

 

To fix the thump, drop the rear drive shaft and grease the splines.

 

Yes I had the same thump just grease the splines and mine was all set.

 

to use synthetic?

 

Not at 5000 miles.. He should be good to go..I am putting in syn 15/40 at 5000 miles on my 6.0 when it gets there..2000 miles now and just love it!!no problems..Will let everyone know how the syn oil affected my start and idle..Now it doesnt smoke or anything and starts very quickly with the factory oil...