AFM Comes Through on a Road Trip

[SacraMaro]

Originally Posted by Swacer

yeah...not real sure about that. My LS3 can get 25-27mpg on the highway going 73mph for 3-4 hours. Firing on all 8.

+1

[gajagfan]

I am curious as to why the lifters or rings for that matter are an issue. We have this feature on my wifes Avalanche, though it seldom seems to come out of V8 mode especially running down the highway. To the OP, we get between 22 and 23 rolling down the highway with cruise set at 79. I think this post should possibly be focused on how poor of mileage your wifes V6 got instead of how great your car did (not that it did bad)! I thought the V6's were supposed to get near 30?

[Tricksta]

Originally Posted by gajagfan

I am curious as to why the lifters or rings for that matter are an issue. We have this feature on my wifes Avalanche, though it seldom seems to come out of V8 mode especially running down the highway. To the OP, we get between 22 and 23 rolling down the highway with cruise set at 79. I think this post should possibly be focused on how poor of mileage your wifes V6 got instead of how great your car did (not that it did bad)! I thought the V6's were supposed to get near 30?

+1

[Indydriver]

Originally Posted by gajagfan

I am curious as to why the lifters or rings for that matter are an issue. We have this feature on my wifes Avalanche, though it seldom seems to come out of V8 mode especially running down the highway. To the OP, we get between 22 and 23 rolling down the highway with cruise set at 79. I think this post should possibly be focused on how poor of mileage your wifes V6 got instead of how great your car did (not that it did bad)! I thought the V6's were supposed to get near 30?

While I am not that familiar with GM's system, I am intimately familiar with Honda's as we have one of their "AFM" six cylinders. The cliff notes version is that steady state highway driving for long periods with one bank of cylinders reciprocating but not firing causes differential cooling allowing oil to escape past the oil control rings, fouling the plugs then exiting the tailpipe. Many people don't check their oil levels regularly and these engines with five quart sumps were losing more than one quart per 1000 miles with a maintenance Minder calling for oil changes at 8000 miles. Oops, no oil.

[PalmerGA]

Originally Posted by kelley1996

I ran a trip 450 miles each way (900 total). Same route same speed no traffic jams at all. First 450 miles AFM on 23 MPG. Plugged in my programmer and bypassed AFM.......23 MPG. Go figure.

I did the same thing when the Range device first came out for our Camaros. Very controlled comparison, equidistance each way (480 miles per), similar conditions, same route, same speeds... got 0.4 mpgs better with the Range plugged in. AFM is a scam that GM contrived to avoid the Federal gas-guzzler tax, tested on an engine only - not real life conditions. The only way I could see AFM coming out ahead is on perfectly flat roads with no headwind.

[rebelyell22]

I get mid to high 20s in my LS3 on the highway

[Austin45]

I just did a 800 mile road trip in my V6 and average 25 doing 80mph on the interstate and 60mph threw the mountians and steep inclines, how did you only get 22 out of the v6? Technically my window stick claims 29mpg lol

[dklowrider]

I did a 150 mile trip all highway and kept my right foot under reasonable control just to see and got 24.5 @60-70 mph.

[Rocky1974]

Originally Posted by Swacer

Is it the rings that go bad, or the lifters? I thought with the L76, the DoD lifters would go bad.

The lifters SOMETIMES go bad. The rings ALWAYS go bad. I know people who had to have them replaced as early 20k miles and as late as 100k miles, but they always have to have them replaced sooner or later. Trust me, if you have AFM and you don't disable it, you WILL be replacing your rings. The only question is WHEN.

[Rocky1974]

Originally Posted by Indydriver

I'm wondering if there has been any reliability issues with GM's AFM. Maybe Gen4 LS's haven't been around long enough. I bought a 2007 Yahoe with it and it still seems to be working fine. OTOH, Honda is settling a massive class action suit over theirs.

You're kidding?......Right? Just Google it. You can read about the problems for days. AFM has become the very definition of problems. We're talking about the world's greatest engines, saddled with the world's worst fuel saving technology.

[Ajdin@A2BMotorsport]

I get 22-23 MPG highway on my car... and its cammed

[sonnydurden]

Originally Posted by Rocky1974

The lifters SOMETIMES go bad. The rings ALWAYS go bad. I know people who had to have them replaced as early 20k miles and as late as 100k miles, but they always have to have them replaced sooner or later. Trust me, if you have AFM and you don't disable it, you WILL be replacing your rings. The only question is WHEN.

Is the AFM still working in manual mode?? I need to research how to disable..

[qcman]

Originally Posted by sonnydurden

Is the AFM still working in manual mode?? I need to research how to disable..

Yes it is if you downshift then upshift I think and then shift manually after that it is turned off. Get a Range its cheap works great and doesn't modify the ECU so it doesn't leave a footprint. Best thing I did with my car other than buying it......

[Gamecock SS]

Originally Posted by Swacer

yeah...not real sure about that. My LS3 can get 25-27mpg on the highway going 73mph for 3-4 hours. Firing on all 8.

Wow. I drove from Va to SC last month. Got 21 mpg at 70-75. Firing on all 8.