Originally Posted By: Realfine69
Here is my opinion having worked for GM for 5 years.
Anyone that has a 2.4L or a 3.6L should use only full synthetic and run it no more than 6000 miles MAX. No more than 4000 miles if your only using the Dexos blend oil. With the full size pickups that have cylinder decativation with 6 quart oil pans (07-13) you should run full synthetic and not let it go more than 5000 miles. If you have the 14 and up cylinder deactivation engine with the 9 quart oil pan you can run the synthetic oil all the way down to 0% or the Dexos approved blend down to 30%. The 2.4 and 3.6 engines saw MASSIVE timing chain failure due to people following oil life monitors. GM even reprogrammed many vehicles to re-configure the software. The early 5.3 cylinder deactivation motors fried oil and burnt it in no time, fouling plugs and causing varnish everywhere chewing up cams and lifters as well. With the 14 and up newer direct injection motors they basically revised the entire engine and added the larger oil pan. With all that being said I ran my 2012 GMC Sierra to 3000 miles and changed it. My 2015 Silverado I use full synthetic and run it down to roughly 10%.
With my wife's 2017 3.6 Impala, I plan on changing it out in the spring no matter how many miles are on it because it is new (to us) and I don't know it's history prior to the 20,000 kms that were on it when we purchased it.
Like what you mentioned, since our first oil change, that was done in the fall, (Nov) I have noticed how fast the OLM descends. It is rather quick or far more quick than I have seen before on any vehicle.
Even though I have heard/read numerous times these new(er) 3.6's aren't like the older ones (much improved, supposedly?) I will still change our's twice a year regardless of the OLM with nothing but full synthetic, like it has now. (PP or PUP)
Aside from all that, it is funny, as humans, how we look/think about things. Not saying with a 100% certainty, but I would assume the manu's have also built in a buffer with their OLMs. Taking one down to "0" shouldn't be a problem, for most, as I would assume the buffer has been built into that number just like the manual states, change oil within a 1000 kms or 600 miles after it reaches "0".