Hello everyone. I have a 2007 chev Silverado with a 6.0 L gas engine. 300,000kms on it. I've recently been told that you can not run a heavier oil in the newer chev engines due to the filter screens for the active fuel management (variable valve timimg valve) plugging or restricting flow. Can anyone confirm this to be true or false. I have been using Mobil 5w30 for a while now but already had to run a cleaner through it once to free up a sticking fuel management valve. I would like to run Rottella 15w40 in mine??

I can't answer, but I'll ask, why change to 15W40? if 5W30 has been working fine, why change? Is it to get to a common oil?

Here is what I know.

1. The 6 liter did not come with AFM, so no worries there. Not sure where you are getting your info. The 5.3 and 6.2 did. The 4.8 did not. Take a look at your the top of your air filter box. It will state your engine displacement.
2. The AFM with the 5.3 had real problems with their AFM
3. The AFM problem went away in 2014 with the redesign of the Chev V-8’s. The 5.3 and 6.2 became Gen 5 engines with a higher pressure oil pump with an electronically controlled solenoid to allow 60psi pressures at highway speed and 40 psi at low speeds and idling. The AFM was completely redesigned. The 6 liter is still a Gen 4 and does not have the updated oil pump system. Nor does it have AFM.
4.There is an issue with the screen on any of the engines. The screen is right below the oil pressure sensor mounted at the rear driver’s side of the top of the block. If that screen plugs, the oil pressure sensor will read 0. I have no knowledge of any other screen other than at the oil pickup.
5.If you want your AFM system to remain healthy in a 2014 onward AFM equipped engine, you need to be running the GM recommended Dexos Oil. This is no place for old school xw40 oil.
6. However, running a xw40 weight in a high mileage 6 liter should not cause problems, in my opinion.

FWIW, the 2019 Corvettes come factory filled with 0w40 now and it has a 6.2 L engine with active fuel management. So GM feels that it's safe to run thicker oils with active fuel management. (they have also stated that they recommend this 0w40 for 2014-2018 Corvetttes too)

You are assuming the AFM system on the LT4 is identical with the lesser engines. Could be but unless I saw proof, I would stick with GM's recommendations for each individual engine.

BenM.....I have 2 words for you BlackBear Performance.

I just had the traditional tune and it woke the truck up in a very noticeable way...yet retains the reliability.

We went through all this clear back in 04-05 as Chrysler brought MDS to the market.

The simple fact is that virtually all oil controlled cylinder deactivation systems seem to tolerate a very wide spread of viscosity. No downside except incredibly small variations in activation.

Just think about a dead cold 30w oil, it's a LOT thicker than it will be at operating temp. yet they kick in just fine as the engine heats up.

6.0s do not have AFM as stated in a earlier post. Sounds like someone was trying sell you something. Stick with a 5w30 maybe a HM oil. No reason for a 15w40 in a LS engine. 6.0s are tough engines and have long lives with standard 5w30 bulk oil. We have around 30 in our fleet at work with 0 problems other then manifold bolts breaking, which is common. Most of these engines have 200,000 + miles some 300,000 and one they recently sold had 425,000, all on cheap bulk no name oil from a 55 gallon drum.

Just keep using 5W30 or if you want try 10W30. The LS V8's don't need thick oil.

Mine is the 6.0 L MAX in an LTZ Silverado. By active fuel management I mean that the engine at cruising speed will drop to 4 cyls. Maybe it was called something different in 2007???

I think you’re right Ben. It was a Vortec and seems to have had a version of AFM. The LS version did not.

That conclusion could not have been applied to the pre-2014 GM AFM system simply because it was a disaster. They came from the factory working fine but many of them wiped out their lifters with time. For the redesign, GM asked for Dexos.

Hold it. I have to stop getting drawn into these high viscosity discussions and get back to the Bitoger chant. “If they ask for 5w20, use 10w40. It’s twice as much and must be better.” Bye for now.