A few months ago we gave you our first impressions of the Range, a device designed to enable the active-fuel-management system on your GM 5.3L engine to run more often. Since then we’ve been using the device and recently ran a fuel economy comparison to see how well it works.
Since January we’ve been driving our 2011 5.3L Sierra using the Range AFM extender module plugged into our OBDII port. It has made a significant difference in the way our truck drives in nearly all circumstances. We’ve driven over a thousand miles with the device and here’s what we can tell you about our experience with it.
First off, the Range does exactly what it states it will do. With the device, our Sierra always tries its hardest to use the active fuel management system (AFM) and engages V4 mode more aggressively than stock. How the device works through the diagnostic port is a little bit of a company secret but the change is entirely reversible, untraceable, and does not damage your engine. When plugged in, the device slightly modifies the signal to your vehicle’s computer, but leaves no lasting changes when unplugged.
We’ve long noticed our AFM equipped 5.3L V8 is a fickle beast to keep on four-cylinders, even when we try really hard. The Range “changes” the way AFM works, making it easy to take advantage of the feature. In our experience once AFM is engaged using the Range, the truck fights to stay on four-cylinders through a much wider spectrum of throttle than you’d experience normally. On flat or slightly uphill grades, we could easily keep speed and even accelerate while on four-cylinders using the Range. That’s something we could never do with stock AFM programming. So, while stock AFM always seemed hesitant to stay in four-cylinders, the Range makes our 5.3L act different . With the Range V4 Max, our truck tries to run with four cylinders whenever possible.
What makes the Range work, keeping AFM active more often, does come with some minor drawbacks. Most noticeably, the transition between V4 and V8 mode can be harsh and abrupt at times. Where GM engineering designed stock AFM tuning to work smoothly, Range engineers focus on keeping AFM engaged longer for better fuel economy at the expense of refinement.
Not surprisingly, in four-cylinder mode our Sierra also felt underpowered. After all, it is running on 1/2 the engine size and longer than GM had intended. On flat roads and highways, that turned out to not be a problem. However, driving with the Range required slightly more mental effort to keep our Sierra moving at speed whenever we drove uphill or through hilly terrain. Whenever we did need extra power,the Range always engaged V8 mode quickly without delay.
We also tried towing a small trailer while using the Range but would not recommend it for longer periods of time when engine performance is critical. Heavy loading seems to cause the system to switch between V4 and V8 too often. Thankfully, unplugging the Range while you’re towing is easy.
Another oddity was that since it’s always plugged into the vehicle’s diagnostic port, we had false errors show up in our monthly OnStar Vehicle Health Report while using the Range. Most noticeably, OnStar could not read for trouble codes and RemoteLink could not access tire-pressure data. While annoying, there was no damage done and these errors fix themselves when the device is removed. We’re told this is expected behavior, as devices connected to a vehicle’s diagnostic port have the ability to override other vehicle computers.
For all the change in the way our Sierra drove, without a daily commute (we work from home), our short and irregular trips around town made it hard to see any direct fuel economy improvement during the winter. While we could always feel the Range working, we quickly realized that through short trips and 4×4 use, our fuel economy actually dropped. Combined with cold temperatures and winter grade gas, the deck was stacked against us getting any real world improvement. We knew that the Range should be producing fuel economy gains but our driving schedule, style, and inclement weather made it impossible to see in hard data.
So, as the weather has gotten warmer, we wanted to do a little test. While not scientific, our first idea was to perform a back to back driving loop. We wanted to get an idea of how the Range stacked up to stock, outside of the random short trips and winter driving we had encountered over the last few months.
We drove Project Sierra over a predetermined rural and highway road loop to gauge how well the Range worked versus stock AFM programming. Driving the same roads back to back, allowed us to compare fuel economy using the same driver, road conditions, and weather.
Both runs started and ended at a gas station so each loop would be tested using the same fuel weight. Our Sierra was also fully warmed up before starting. For consistency, we completed each loop in nearly identical time and average speed, measured via GPS. Through concentration and a little bit of luck, only 50-seconds and 0.6mph differed between the two back to back runs. All effort was made to drive our Sierra in the same manner for each loop. After only 60 miles, the results came out clearer than we expected for an unscientific test.
Stock, we completed a 30.8 mile loop in 44:21 minutes at an average speed of 41.64mph. During this loop our Sierra recorded an average fuel economy of 20.9-mpg, as displayed via the driver-information-center.
With the Range, our 30.8 mile loop was completed in a comparable 45:10 minutes at an average speed of 40.9mph. With the same driver, same road, and same weather, we saw a DIC reported average of 21.4mpg.
That comes to a healthy ½-mpg improvement. Also impressive, considering we’ve never gotten fuel economy that high out of Project Sierra in the past during any time of the year. Until now, our lifetime fuel economy average for our 2011 Sierra has been around 16mpg, as reported by OnStar. During the winter with our short trips and four-wheel-drive use, we often saw that figure dip to 14mpg or worse. While we always caution folks to not rely on driver-information-center fuel economy, a number north of 21mpg is impressive for comparisons sake.
So is 30 miles enough to say the Range definitively works? Scientifically, no. However we wanted to see, under a controlled route, if the Range made any improvement at all. Not surprisingly it did. Since our quick loop we’ve burned several tanks of gas with the Range V4 Max and our experience remained consistent.
Depending on what type of rear end gears, transmission, and what route you drive, the average driver should see a fuel economy improvement while the device is in use. Since everyone’s driving style is different, it’s hard for us to tell you exactly how much the Range will effect your own fuel economy.
Our 6-speed automatic equipped Sierra ran great with the Range V4 Max Module but if you have an older 4-speed automatic, try out the company’s Range V4 Plus module. The V4 Plus is described as better tuned on the highway for vehicles with less transmission gears.
Don’t take our word for it, read this thread for other member experiences with the line up of Range Modules.
Do you have a Range? Comment in our new thread for this article. We want to hear what other Range owners are experiencing.
Do you loathe AFM? If you’re looking for the exact opposite effect, disabling AFM entirely, we’ll be testing Range’s V8 only option in the near future.
GM-Trucks.com Range V4 Max Hands-On Conclusion
The Range does exactly what it claims to but it’s not a magic bullet. Used as a tool, the device allows you to take advantage of your trucks ability to run on fewer cylinders. In our personal experience that can lead to better fuel economy depending on how and where you drive your truck.