2020 GMC Sierra Lifters and Cam gone just outside warranty…

[HyperMOA]

Originally Posted by elkhunter11

So why don't GM's own fuel economy numbers show those drastic fuel savings? Why don't the EPA and Transport Canada numbers show the drastic improvement? Coincidentally, all of their numbers are derived from actually running the engines on a loop that simulates actual driving conditions that result in some cylinders being deactivated at times.
Out of curiosity, if you drove your truck on the highway for an hour, how many minutes do you believe it would only be running on one cylinder? Under what conditions do you believe that the engine would disable 6 or 7 cylinders?

I have asked you numerous times; what displacement does the ratings rate the engine at? I am betting the government rates that engine as a 5.3l and that is it. When it has the ability to effectively reduce its displacement then you are only using fuel of a 2.7 litre. Or whatever. Displacement is one of the largest variables of fuel use.

It runs on one cylinder whenever the load allows. How often is irrelevant.It has the ability is the point.

How is that people can literally prove to you mileage claims and you can’t seem to understand it? You have claimed that the AFM might save 5% max before and I have proven to you a savings of 30% over your precious government energy guidelines. Is it just possible, and I mean absolutely outside the realm of reason, I am talking end-of-times stuff here, that you could be wrong about one thing in your entire existence? No, who am I kidding, that can’t be it.

[elkhunter11]

Originally Posted by HyperMOA

I have asked you numerous times; what displacement does the ratings rate the engine at? I am betting the government rates that engine as a 5.3l and that is it. When it has the ability to effectively reduce its displacement then you are only using fuel of a 2.7 litre. Or whatever. Displacement is one of the largest variables of fuel use.

It runs on one cylinder whenever the load allows. How often is irrelevant.It has the ability is the point.

How is that people can literally prove to you mileage claims and you can’t seem to understand it? You have claimed that the AFM might save 5% max before and I have proven to you a savings of 30% over your precious government energy guidelines. Is it just possible, and I mean absolutely outside the realm of reason, I am talking end-of-times stuff here, that you could be wrong about one thing in your entire existence? No, who am I kidding, that can’t be it.

Obviously, you have no idea how those ratings are arrived at. The government doesn't "rate" the engine at any displacement, they actually run the vehicle on a dynamometer that simulates actual driving. As such, the AFM or DFM will actually deactivate cylinders based on the load, just as it would deactivate cylinders driving on a road. And they have actually adjusted the testing procedures over the years, to make it very representative of what the vehicles actually produce. That is why vehicles don't exceed the ratings by 30%.

https://natural-resources.canada.ca/...-testing/21008

https://www.caranddriver.com/feature...mpg-estimates/

So the automakers test their own vehicles, using the standard tests, and the EPA randomly verifies some of the automakers results by retesting.It is in the manufacturers best interests to achieve the highest rating the engine can deliver, so they aren't going to rate them 30% less fuel mileage than the engine actually
produces. Notice how close the EPA test results are compared to the automakers. Yes that says 3%.

The EPA says its test results are almost always very close to the automakers’ numbers. When they don’t match, a long discussion ensues. According to the rules, if the EPA retests a vehicle to assess an automaker’s results, the fuel economy should be within three percent. If not, the automaker can choose to accept the lower of the two sets of numbers or request one additional retest

[amosfella]

Originally Posted by HyperMOA

I have asked you numerous times; what displacement does the ratings rate the engine at? I am betting the government rates that engine as a 5.3l and that is it. When it has the ability to effectively reduce its displacement then you are only using fuel of a 2.7 litre. Or whatever. Displacement is one of the largest variables of fuel use.

It runs on one cylinder whenever the load allows. How often is irrelevant.It has the ability is the point.

How is that people can literally prove to you mileage claims and you can’t seem to understand it? You have claimed that the AFM might save 5% max before and I have proven to you a savings of 30% over your precious government energy guidelines. Is it just possible, and I mean absolutely outside the realm of reason, I am talking end-of-times stuff here, that you could be wrong about one thing in your entire existence? No, who am I kidding, that can’t be it.

You might just have a unicorn. Don't say anything about your mileage in dealerships. I had a friend that had a unicorn, bragged about it at the dealer while they were working on his vehicle, and when it came out, it was back to standard.

[Tungsten,]

How did running on 1 cylinder get into this? It runs on 4 I believe when you lift a little on the pedal.Scenes less demand ect..

[CBintheNorth]

Originally Posted by Tungsten,

How did running on 1 cylinder get into this? It runs on 4 I believe when you lift a little on the pedal.Scenes less demand ect..

You are correct. It's 4 cyl or 8cyl.
Unless most driving is done under 90km/hr at steady throttle, it doesn't spend much time in V4.
At an idle It's in V8.

[Jamie Black R/T]

Originally Posted by CBintheNorth

Unless most driving is done under 90km/hr at steady throttle, it doesn't spend much time in V4.
.

Ive tested this in our AFM tahoe running to and from Calgary a few times...if you are keeping with the flow of traffic...it spends no time at V4.

Still great on fuel when compared to an older 2500 gasser with a 4 speed

[elkhunter11]

The new system is DFM rather than AFM, the DFM can run on 8,6, 4 and even 2 cylinders. Some people claim that theoretically, it could even run on 1 cylinder, but the reality is if you are driving on a highway with the flow of traffic, the load would never be light enough to run on 2 cylinders for any significant amount of time. And even with DFM, GM only claims a maximum improvement of 12%, under ideal conditions, so if you are driving a constant 90km or less, on perfectly flat ground, with no wind, you might see 12%. If you look at the claims made by the companies selling devices to bypass the DFM, they claim less than 5% difference in fuel economy. Ford runs their own version of DFM on the 5.0, and claims an improvement of 2-3% in normal driving.

[W921]

Back in the 80s new trucks had a claimed mileage on build sheets in the windows on car lots. They had city and a highway claimed mileage. You never ever would get the claimed mileage regardless of Ford,Chevy,etc.
With towing and old vehicles you don't gain with smaller engines. Takes so much power to do the job so smaller engine just working harder.
Empty or idling around a small gas engine is alot more economical.
I'm not driving big blocks to go on trips to Calgary or Lethbridge like I used to.

[Stinky Buffalo]

Originally Posted by elkhunter11

Ford runs their own version of DFM on the 5.0, and claims an improvement of 2-3% in normal driving.

And that's the thing right there - I used to be big into mileage-saving devices, did a lot of experimenting etc. Spent an inordinate amount of time on forums dedicated to mileage saving tips, tricks and gadgets.

The one thing that was a given - anything under a 10% improvement was negligible - basically any claims of 10% or less were considered inadmissible in terms of proving any kind of improvement.

10% can easily be influenced by factors such as wind speed/direction, vehicle weight (and how much fuel contributes to the weight), load, tire inflation, effects of temperature on tire inflation, traction, traffic, minor variations in driving habits etc. - not to mention variances in fuel blends - and so on and so forth...

Remember the "hypermilers" from the early days of Hybrids? They would accelerate painfully slowly, avoid using brakes when approaching stops (so they would begin decelerating much earlier). They would ride on the painted lines to reduce road friction. The bane of rush-hour traffic. Then they would post online about the incredible mileage they were getting with their hybrids...