Dave502

dvilin

With a M7 you must put it into ECO mode not so with the A8.

Foosh

The only OEM way to avoid V4 mode in the A8 is to put the shifter into the manual shift position and use the paddles. Tuning it out is an option if you don't care about having your powertrain warranty blocked.

Skid Row Joe

If it's the M7, (manual transmission) then, yes.

If it's the A8 transmission, then no, it will always engage V4 mode.

Dave502

Woodson

Also worthless in the M7 imo.

Rebel Yell

The A8 transmissions are designed to go into V4 mode any time the parameters are met, and that is a lot with these trannys. The Eco mode with an automatic just keeps the car in V4 mode longer while cruising at highway speeds, and the engine with still move between V4 and V8. The V4 mode can be defeated in two ways that will not void the warranty. The first way if to put the trans in sport mode, and shift with the paddles. The second way is with a Range Technology AFM (V4) disabler. www.rangetechnology.com. Many here use the Range unit.

LuisZ51

How so? On long highway trips it saves gas for me.

Foosh

Yes, it's great for that. Another thing I like about the M7 is that I never have to see V4 unless want to save some fuel while cruising at 70 in 7th on a road trip by switching to ECO. On the A8, it can go into V4 in any mode, unless you switch to manual shifting.

Woodson

Personally I'd rather avoid any potential V4 issues in order to save a few pennies. I haven't seen any quantifiable proof that it even saves any gas, especially at little over idle RPM's in 7th.

KenHorse

Can't speak (yet) for my Grand Sport but I was reluctant to use it in my '14 Z51 M7 until one day I did. It did make a small difference in mileage for me - maybe 1 to 1.5 MPG on longer highway trips increase.

Quite literally, your mileage may vary

Patman

I have found it gives me about a 5% boost in MPG so that's pretty significant.

I'm not sure what issues you'd be worried about with the M7 and V4 mode though. I know a lot of A8 guys try to avoid V4 at all costs to avoid any torque converter issues, but I've never heard of anyone with an M7 having a problem related to AFM. If you're just going to be cruising along for long periods of time on the highway you might as well use it, it's free money in your pocket.

owc6

Yes, and no.

Putting an auto into ECO will extend the parameters that the car will go into, and remain in V4. It may be only slightly, it may or may not be important to you, but that's what it does.

Maxpowers

I can't stand the way I can feel it when it switches in and out of V4 mode when cruising down a long stretch of highway. It is very slight (my wife can't tell), but I can and it drives me nuts.

Parcival

Woodson

Yeah, I turn off the auto shut-off on my wife's Merc when I'm driving that. The annoyance isn't worth the pennies saved imo.

Mayor111

Im not disagreeing with you Patman - Im also no mechanic so this is just purely guessing here - but would you think that the cost to repair the mechanics and technology behind changing from V8 to V4 is "unnecessary" given the few bucks you might save annually? In other words you said its a 5% savings. So lets say you get 30 MPG in V8 mode...if you increase that by 5% you then would get 31.5 MPG... If you have (just for ease of math) 15 gallons in your tank at all times - then your getting an extra 22.5 miles more each tank - that's about $3 worth of gas per tank-fill. So does $3 of gas (22.5 miles) really equal the major cost of issues that "could" arise in the engine by switching from V8 to V4? Again - I dont know - Im asking.

lakemg

I frequent this site a lot and I have yet to see any engine failures or needed repairs due to the engine switching between V8 and V4. Now if we roll back to 2009 during my Pontiac G8 GT days, yes we saw quite a few failed lifters because of the DOD design, but that was a Gen IV engine and I've not seen that issue with the LT1 engine, at least not yet unless I missed it.

On the other hand, I do see issues here with the A8 transmission, due to the V4/V8 technology...

Patman

You raise a valid point, but so far it does seem like the AFM hardware itself is pretty solid on these cars, as I can't recall a single person on here reporting any issues in that regard just yet. I guess we'll know for sure once more owners start getting much higher mileage on their LT1s (and they'd have to be owners that use the AFM frequently, like myself)

yokennyr