9th Sep 2018, 12:52

Right from GM. See the section:

"How The AFM System Can Cause Excessive Oil Consumption"

https://www.gmpartsonline.net/blog/engine-oil-consumption-solutions

This has lead to the saying for DoD "disable or doomed".

15th Jul 2019, 02:02

Original Reviewer with an update.

At around 73,000 miles my engine began to develop a pretty noticeable lifter tick. This is usually a sign that one of the AFM lifters is about to collapse, so to prevent severe damage from occurring I decided to just completely remove all of the AFM components.

This is an extremely involved job. The cylinder heads will need to come off to access the lifters and the timing cover will require removal in order to swap out the camshaft. I'm an ASE Master Tech with access to a full shop. I would not recommend this job to the DIYer.

The kit to remove the AFM system was around $600. To remove the AFM system you will need: 16 new NON-AFM lifters, 1 NON-AFM camshaft and at least an upper engine gasket set with head gaskets. (The original AFM cam cannot be used because it has a different profile lobe on the AFM cylinders. Attempting to reuse it will result in misfires and low compression on 4 of the cylinders.)

I decided to just preemptively replace many internal components while I had the engine apart. I also replaced the timing chain, VVT gear, oil pump and pick-up tube.

Melling makes an excellent oil pump, but make sure you use the M365. I learned this the hard way with the M295 that came with my delete kit. The M295 will happily supply enough oil to prevent any engine damage, but it cannot produce the pressures required to operate the AFM system. The reason this is a problem is the engine computer will set a code indicating "Oil Pressure Out of Range." I drove for a few hundred miles with the 295 installed and suffered no engine damage as a result, but the ECM wasn't happy. I had to drop the oil pan again to install the 365. No codes after that. Sucks because the ECM was essentially panicking about a system that the engine is no longer equipped with, haha.

Needless to say, you will need to have a tuner to shut off the AFM system if you perform this work.

I still love my truck and I think it was worth the time and effort to do this. But if you do not have the resources or knowledge to perform this kind of work, this is a serious issue. It's really a shame that GM installed this unreliable system on an otherwise completely bulletproof engine. Either way, no worries for me anymore! My AFM was shut off for years, so my MPG did not change at all after replacing the mechanicals with Non-AFM parts; still averages about 18 MPG in mixed driving.

75,000 miles now and running great.