I'm on the cusp about AFM use in my C7. I've done a lot of research on the subject and the folks that have an issue with AFM seem to be a large group and aren't shy about expressing their opinions. Primarily their complaints are 1. AFM causes a variety of drive train failures and 2. "I didn't buy a Corvette to run on 4 cylinders." There are only a few advocates for AFM. My question is for those that use AFM all the time. How many miles have you racked up using AFM and have you experienced any mechanical problems directly related to its use? In my opinion, the "shudder" issue is a product of inferior transmission fluid so let's rule that out right from the start. Again, I would like to hear only from those C7 owners that use AFM 100% of the time.

 

We've got 43k miles on our 2017 Z51 A8 and no problems.
People who don't have problems, usually don't say much.

 

That's exactly why I posted the question. I want to get the other side's opinion. Thanks for your input.

 

I have never had my car go into 4 cylinder mode (Range AFM Eliminator installed), but will be interesting to hear the experiences of those that have kept the AFM active over an extended period of time.

 

I currently have 28,000 trouble free AFM miles. So I'm curious to see if I'm the exception or the rule when it comes to the V4 issue.

 

The AFM deactivates 4 cylinders by using a special valve lifter on each of the 4 cylinders that is hydraulically actuated. Then the valve stays shut, no fuel in. There are threads in these Forums reporting failure of these valve lifters and sometimes resulting in catastrophic engine failure. GM has had cylinder deactivation for many years. But I elect not to use AFM as the savings isn't worth the risk for me.

David

 

I have a 2019 Silverado. 30 seconds after the warranty is up I’m either going to sell it or send my ecm off to hp tuners to be unlocked while I deactivate the AFM and possibly VVT although I do see benefit in VVT the cam phaser is a weak point in the system. Also that stupid auto shutoff, what a POS that is.

The key to long AFM life is CLEAN oil at appropriate levels, the majority of folks who don’t have issues keep their engines well maintained.

 

I have a 2015 Z51 Coupe with just over 100K miles; #5 cylinder lost 55lbs of compression and was tracked down to the AMF lifter hanging the valve open. Most of the time when the AMF lifters collapse, the make lots of tappet noise, mine was quiet and caused a misfire. The car is in the shop being disassembled; if the cam is bad, I'll pull the whole intake system and replace it with cam kit of lifters, pushrods, cam, etc. from John Page at 21st Century. The price is a lot less than replacing all the AMF lifters and Cam and all the rest of the connecting stuff..

I have never minded the 4cyl mode and have never experienced drive train shutter. I would prefer to go with the old school proven valve train than chance another AMF lifter going bad during the next 100K miles. There are way too many moving parts with the AFM lifters......not to mention all the electronics that go with it.

I also have a 2016 M7 that never goes into 4cyl mode.....we'll see if that will extend the life of the AMF lifters.

Enjoy the ride

 

I have a 2015 Suburban, 69 miles before the extended warranty expired the AFM system failed. $3,500 repair cost me a $200 deductible. Engine oil and filter had been changed religiously every 5,000 miles, always with Mobile 1, so unfortunately clean oil doesn't always prevent issues.

 

37K, no problems with the AFM kicking in.


Elmer

 

I use mine when I am on the highway - not full time but at least half of my miles are all highway - so I'll weigh in as a proponent of the system. No issues whatsoever. Sure, I didn't purchase a C7 with mileage as a top issue, but if I can have better mileage with no loss of performance why not? The reality is the vast majority will not see issues; those with issues (either perceived or actual) will be the most vocal. I almost did not buy a Vette because of all the issues I saw posted here way back in 2014. Glad I chose to go for it!

 

How many miles on your engine?

 

 

I don't use it 100% but I use it quite a bit. I have a Z06/M7 so I have to choose to use AFM by switching to Eco Drive Mode. The results are hard to characterize. AFM operates in M7 gears 4, 5, 6 and 7. On the highway in 7th gear with the cruise set at 70 mph the engine switches back and forth from V8 to V4 operation. If the road is level or has a slight down slope it will shift into V4 mode. However, any slight added drag on the drivetrain and it will switch back to V8 mode. Switching is damned near seamless and undetectable except by displaying the mode on the IP or by putting exhaust in permanent track mode. When the engine is in V8 mode the exhaust is loud and when it is in V4 mode it is quiet. The increase in MPG is maybe 1 mpg at that speed.

I have found that dropping down to 6th geat at 70 mph in cruise nets better MPG. It might be 2 mpg Vs 1. The difference is due to the increased torque available in 6th gear. The engine switches to V4 mode and it takes a much larger increase in drag before it switches back to V8 mode.

There is no throttle lag due to the switch. If it is in V4 mode and I hit the throttle the engine switches to V8 mode quickly without any sag, hesitation, or bog. The car accelerates just like the engine had never been in V4 mode. What is nice is to drive around town where most of the gear selection is in 4th through 6th. It definitely helps the around-town mpg since in 4th gear it takes a hell of a load increase to switch back to V8 mode and doesn't hurt street performance. Not sure how other drivers respond to the change in exhaust noise when the engine switches modes. You go from a near-silent exhaust to a Loud Bang if you add noticeable throttle while in traffic.

Bill

 

Only 20K...

 

Just a question to those who use AFM.. Im not sure why you wouldn't use a Range device to disable AFM? The mileage savings is minimal (if at all) and the risk of engine failure isn't worth the pennies you're saving in gas. I look at the Range device like insurance... I've never been in an accident after driving 35 years - but I still pay for insurance (just in case). The $188 Range device is the best "insurance" you can buy.

 

A reasonable observation but that's not what this thread is about. You can find plenty of statements from the owners that don't use AFM and their reasons for not using it. I want to hear from those that have used it, if they exist, and what experiences, good or bad, they've had. I'm hoping to get first hand experiences regarding the long term effects of using AFM. Not anecdotes or the quoting of some "expert" from a magazine article.

 

In my '14, now '16, combination of 75,000 miles, use constantly, no problems.

 

I have a stick so I can avoid AFM when I want, but have to ask is there really a measurable risk? Some have lost engines for a host of reasons but xxx number of people on a forum stating that "AFM killed my engine" is simply not a scientific study. GM is using this system in a host of vehicles, some of which are their biggest sellers. If there was a design defect wouldn't we have seen data to show that? Remember the intake gasket fiasco with DexDeath? Other than a few people on forums there does not seem to be a design problem...perhaps some defective components but that would be limited to those vehicles that had the bad parts...I thought the primary reason the Range people blocked AFM was because of concerns with the transmission/torque converter failing. There are plenty of transmission issues - that is for sure - but I blame the design of the transmission for that. AFM might be stressing the torque converter but that is not an indication that AFM is bad; rather the design of the transmission is inadequate.

 

The whole AFM issue is blown out of proportion on the forums when it comes to stock or mild bolt on cars. If you like the fuel savings then keep using it and have no worries.