Oil for GM 3.6l famous for timing chains.

[GMBoy]

It actually does not matter what oil in that generation of 3.6L as they were doomed to failure. It was not if but when the chains went. Here is my "data" I use to support my opinion. My parents and I both purchased new 2008 Cadillac CTS's with the 3.6DI motors. I did Mobil 1 every 5k miles and my dad ran his personal favorite Redline and went by the oil monitor so figure 7-10k miles (before the GM software revision that shortened the OCI). My Dad had chains done under warranty at around 42k miles and I needed them at the 55k mark. So the "better" redline made no difference and my changing "early" at 5k with Mobil 1 made no difference either to the final outcome - chains went bad.

Note - I still have this CTS and its at 202k miles on those timing chains done at 55k so the revised chains fixed the issues.

 

[4WD]

Here's what the inside of our 2006 Outback's engine looks like after 15 years and 96,000 miles of using nothing but Pennzoil conventional 5w-30 changed every 3-5k miles.

There is no oil in that photo - so how would anyone else know it had not been cleaned before the picture ?

 

[RyanY]

I've been doing 3k OCIs and 0w40 syn oil. The chain's been cooperating just fine.

3k OCI may be the best advice for the HFV6, as recommended by a Cadillac specialist called Northstar Performance. That shop appears to be OOB, but their explanation for the 3k seemed logical and was, presumably, based on experience. They suggested that the HFV6 chains failed because of low oil level, not poor quality oil. I followed their advice since 2018 when my OG chains failed, and I prefer not to change them again!

My observations are consistent with Northstar Perf's explanation, but I am far from having real data to support my practice:
IME the HFV6 consumes more oil as the OCI progresses, and I have noticed fuel dilution on some occasions (but not usually). The increased consumption appears to be related to the PCV system which sucks more oil as the OCI approaches 3k than it does with fresh oil (as indicated by the pool of oil in the bottom of the air box located in front of the throttle body). I speculate that the older/sheared oil is more likely to be sucked into the PCV than newer oil. I considered UOA, but instead decided to just change it every 3k and move on with life...after all, even though the engine is running well, the rest of the car is over 15 y.o. and approaching EOL.

If the car were younger and/or I didn't have a huge stash of Magnatec 5W30, I would follow @Triple_Se7en and try 0W40 for a few OCs. Starting with the higher viscosity euro oil may delay the PCV issue (if my speculation is correct).

 

[Slick3914]

Probably was the Mobil 1 he was using . M1 has cheapened there base stock from what I was told . Customer have been experiencing louder engine noise no increase in MPG’s and Stretched Timing Chains . M1 been Relying on there heavily advertisement through sponsorships for years now. Happy Holidays everyone

Please provide some actual evidence to your claim. Thank you.