V8 vs V4
Melting Slicks
Joined: Aug 1999
Posts: 3,422
Likes: 9
From: Rockaway, NJ
On a 1300 hundred mile trip I did the first 650 in Reg V4 mode with the A8 it was shifting continuosly and got 29.4 MPG. On the second 650 mile segment I used the Range V4 disabler and got 28.9 MPG, both segments were at 78 to 80 MPH, in my opinion the disabler is the only way to go.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
Originally Posted by kitesurfer
i'm at 400 miles now...didn't know there was 4 cyl operation before 300 miles, and didn't know anything was wrong until this thread. does anyone really read their owners manual the first day? my wife accused me of babying the car which makes me believe if was probably running on 4 cyl.
Sr.Random input generator
Joined: Jan 2008
Posts: 7,798
Likes: 2,229
From: Sammamish, WA
They might have had to leave it on to be considered for EPA certification, especially for the automatics. I tried it before the first 500 miles, but didn't use it for a long time until I hit 800 or so.
Instructor
Joined: Aug 2016
Posts: 213
Likes: 64
For engine longevity you do not want it continually going from Firing on 8 cyl to 4 cyl. When I picked it up from the museum they told me to keep the A8 in manual so it would fire on all 8 cyl during the 500 mile break in.
It's not the best for the rings and Pistons in the 4 cylinders to not be under compression. These engines tend to use more oil after about 40,000 miles.
Google AFM (active fuel management) and GM engines problems you will find plenty of evidence of this. In fact my 2013 Avalance with 50,000 miles started using oil and had to have new rings and Pistons installed, I was lucky that it was still under warranty. You can sometime feel the engine vibrate as its going back to 8 cyl if you give it light throttle I put the Range AFM eliminator on the Avalanche after the rebuild and I also put one on my 2016 ZO6. If you aren't going to keep the car to that mileage then it's probably not worth doing anything.
Here is one article.
http://www.tundraheadquarters.com/bl...l-consumption/
It's not the best for the rings and Pistons in the 4 cylinders to not be under compression. These engines tend to use more oil after about 40,000 miles.
Google AFM (active fuel management) and GM engines problems you will find plenty of evidence of this. In fact my 2013 Avalance with 50,000 miles started using oil and had to have new rings and Pistons installed, I was lucky that it was still under warranty. You can sometime feel the engine vibrate as its going back to 8 cyl if you give it light throttle I put the Range AFM eliminator on the Avalanche after the rebuild and I also put one on my 2016 ZO6. If you aren't going to keep the car to that mileage then it's probably not worth doing anything.
Here is one article.
http://www.tundraheadquarters.com/bl...l-consumption/
Racer
Joined: Apr 2016
Posts: 478
Likes: 104
All the talk about engine longevity is irrelevant. No one is going to run a Corvette motor for 300k miles. This isn't a Toyota pickup truck and 99.9% of corvettes will never even see 100k miles.
I have the Range AFM disabler in my 14 Z51 A6. When on extended highway stretches, I set it to Eco and turn off the disabler (AFM is enabled) to maximize the mpg. When around town, I am usually in sport/manual or touring with AFM disabled.
The only thing I don't like about V4 mode is the noise. The oil scavenging pump makes a funny running water sound, though that could be more a result of my dry sump and not entirely AFM related.
Anyway, I am a believer. I will take the 1.5 - 2 mpg benefit that I regularly see with AFM enabled.
I have the Range AFM disabler in my 14 Z51 A6. When on extended highway stretches, I set it to Eco and turn off the disabler (AFM is enabled) to maximize the mpg. When around town, I am usually in sport/manual or touring with AFM disabled.
The only thing I don't like about V4 mode is the noise. The oil scavenging pump makes a funny running water sound, though that could be more a result of my dry sump and not entirely AFM related.
Anyway, I am a believer. I will take the 1.5 - 2 mpg benefit that I regularly see with AFM enabled.
Last edited by xxaarraa; Sep 6, 2016 at 12:21 PM.
