OP might be using the right oil but I did not see it mentioned so I figured I better put it out there if it can save them a trip to dealer.

 

Yeppir, if it doesn't have 5W-20, the MDS won't work.

 

Yes it's 5w-20.. But i dont know if it's SAE.. I will change oil and filter this week end, and if it does not work I will bring it to the dealer for a test drive.

 

All oil is SAE. It must pass their standards before being able to be labeled as 5w-20. The oil also must pass strict standards to be up to spec such a J or whatever the newest revision is.

Prob need to look elswhere such as stored Active DTC codes which cannot be pulled by the basic scanner. You need a Handheld Tuner/programmer or a DRB-III or Starscan tool that the dealer has.

 

I used to run 5w20 until my brother said he wasn't a fan of it, and preferred 5w30 or 10w30.

The last oil change I put in 10w30 and MDS is still working just fine. I can tell when it kicks in and out because of my exhaust.

 

Ok well my best bet will be to go see the dealer.
Wheb MDS kick in, does the truck rev higher?

 

Did you gas mileage decrease a little bit?

The 10w-30 or even 5w-30 will make the MDS kick in less often, and it isn't the right oil to coat the cylinder walls when the MDS does kick in, so you are risking damaging them whenever the MDS kicks in.

Back on topic.

I agree that there might be some hidden codes being produced, otherwise there is something wrong with the programming on the truck. I suggest bringing it to the dealer and having them do a work-up on it.

By the way is your truck by any chance a "Mega Cab"? As that might be why your MDS isn't kicking in... as the Mega Cabs didn't have MDS from what I understand.

 

I haven't noticed any decrease, but my truck doesn't commute anywhere, so I don't get a 'standard' fuel economy.

However, I don't see how cylinder wall oiling changes when the cylinders shut down...

 

I was always told the 06 mega cab didn't have mds and the 07 and on does. I can confirm though that the 06 does mds. Or at least I assume as I will be driving at 60 mph and rpm sitting around 1800 and then will drop to about 1000 while just cruising.

Oil doesn't have anything to do the cylinders that are shut down but more with the cylinders that are still firing. The wrong oil in the engine will change the resistance of the piston against the cylinder wall and if the resistance increases requiring more force to lift the cylinder then it will delay the or prevent mds from kicking in.

 

My 06 @ 70mph aprox 2000 rpms the tach will jump about 50-100 rpm when MDS kicks in....that's w/ 3.92 gearing.