AFM Lifter Failure Average Mileage?

[tom3]

From what I've read when the motor is in the 4 cyl. mode those four cylinders are pulling their guts out at time. Much like an actual full throttle mode. I suspect this is what causes some of the oil consumption after some mileage. Could be why some people complain about the engine vibrations with this system. I do like the mileage increase and the technology is pretty awesome, but those gizmo based lifters scare me too.

 

[Marky Dissod]

The dormant cylinders are supposed to be acting like air springs.
Those cylinders are thus subject to greater thermal variations, more often than the always active cylinders.

If you let V4 mode cool the dormant cylinders for too long, ask Chrysler what happens.
GM never pushed it that far, but the 4 sometimes-dormant cylinders wear themselves down at faster rates compared to the always-active cylinders.
My guess is that's how the increased oil consumption occurs over time.

But whether it's the lazy cylinders or the overtime cylinders that will progressively consume more oil, point is, use of V4 mode increases oil consumption, even if the V4 lifters never fail.
And the design of the V4 mode lifters is more likely to be outlasted by the V8 mode lifters.

However the V4 mode lifters' weakness can be minimized / delayed by disabling V4 mode in the software.

Most of us would gladly lose several MpGs if the gain was spending less money to maintain / fix a powertrain that will also last longer by avoiding or minimizing its weaknesses.

(If you need MpG that badly, then have your spark maps custom-optimized for 91 octane, and very seriously consider 3.23, 3.42, or 3.73 to take a bit of load off of the powertrain.)

 

[RST Dana]

Don't think I understand the question. Please rephrase?

As a livery driver your mileage should have well exceeded the lease amount and usually cost additional dollars at the end of the lease. In the neighborhood of $.25 per mile.

 

[Marky Dissod]

As a livery driver your mileage should have well exceeded the lease amount and usually cost additional dollars at the end of the lease. In the neighborhood of $.25 per mile.

I was permitted to 'buy' the truck out of the lease before it exceeded the allotted mileage.
I was making quite a bit over $0.25 cents a mile until about 2018, when I gave up on livery driving, and sold the truck. I came out ahead, at least in terms of money anyway.

 

[TollKeeper]

As a livery driver your mileage should have well exceeded the lease amount and usually cost additional dollars at the end of the lease. In the neighborhood of $.25 per mile.

Usually thats the case, unless you purchase it at the end of the lease.

 

[BG1988]

FYI, I was a livery driver in NY / NJ / CT / PA, although over half of the miles were accrued in Manhattan.
The vehicle in question was a 2012 GMC Yukon XL with a flex-fuel 5.3L V8.
In an attempt to improve city MpG, I had a tuner INCREASE the V4 duty cycle.
V4 mode was made available whenever the road speed went over 21MpH.

I put over 185K miles on that Yukon XL in roughly five years.
Oil consumption became a problem, usually had to add 2 quarts between every oil change.
The lifters never failed, likely because the motor oil was changed 8x a year.
The additional oil consumption hints (to me) that the rings of the colder V4 cylinders wore the bores slightly.

Since it was a lease, I can't say I regret taking even more advantage of V4 mode than GM originally intended.
Had I intended to keep that vehicle, allowing ANY V4 mode enablement would have been a mistake.

the issue is hypercycling of the v4 mode... it's most likely because of sludge build up from lack of oil changes that causes the failure i thought mine was failing but it's just an exhaust leak you can really smell it on startup outside of the SUV

I get P0420/430 in the winter time ..i'm going to start running AFM again because of gas prices 26-28mpg is better then getting 23

 

[Marky Dissod]

... most likely because of sludge build up from lack of oil changes that causes the failure (of V4 mode lifters) ...

1. I changed my oil more than often enough.
Superior oil filtration capable of screening finer particles would also be helpful.
I actually think one has to change the oil so often, because oil filters are not quite good enough at their job.
Unfortunately, oil filters are not more precisely rated (which also keeps them from improving).

Using an oversize filter might be of some help.
Using an oil filter better capable of filtering out unusually finer particles would also help protect the V4 lifters from their weakness.

2. My experience with 'overuse' of V4 mode leads me to surmise that the 'sometimes' cylinders change temperature by enough to wear down their rings and cylinder linings at a faster rate than the 'always' cylinders.
In effect, the 'sometimes' cylinders age more rapidly.

What I'm saying is, instead of simply reactivating V4 mode to its previous settings, it may be wise to alter those settings, so as to keep the 'sometimes' cylinders from getting as cold as GM's original settings allow.

Your mileage may vary.

 

[40Rouge]

I recently had the AFM concern at 76k miles. I've been driving for a while now in "L9" mode to keep the engine in v8, but I recently purchased a Range AFM disabler so I don't have to keep doing the L9 hack. The Yukon feels so much better in constant v8.

For anyone that doesn't know, putting it in L9 drive will keep the car from shutting down cylinders. It's a "hack" to get around AFM. Plenty of Youtube videos on it.

 

[Marky Dissod]

Disabling V4 mode will increase the lifespan of the V4 lifters; by how much is not possible to predict, but the sooner the better.

Obviously DELETING V4 mode hardware / replacing with proper V8 hardware (including proper V8 tuning) is the best course of action to take in the long run.

 

[LANCISTUL]

Disabling V4 mode will increase the lifespan of the V4 lifters; by how much is not possible to predict, but the sooner the better.

Obviously DELETING V4 mode hardware / replacing with proper V8 hardware (including proper V8 tuning) is the best course of action to take in the long run.

I agree. My 2012 Suburban is a fine example of this. Bought it at 130k, immediatly disabled AFM via software, now I'm at 350k (yes you read right) original engine untouched. I had the tranny rebuilt at 260k, and thats it, that's the only big service. Starts every morning, no issues. 5.3 LC9