Hypermiling a Ram 1500 EcoDiesel to 38.1 mpg
Fri, May 9 2014
Which is why we always answer the phone when Gerdes calls. He likes to take journalists along on his drives, not only to try teach us how to hypermile but also to prove that we can be taught. The first time I 'helped' him and his team was when we got over 30 miles per gallon in a 2011 Ford F-150 XLT with the EcoBoost 3.5-liter V6. The EPA rated that truck with at just 16 mpg in the city and 22 on the highway. So, we'll count that trip as a success.Our latest adventure appeared, at first glance, to be nearly impossible.
Next up was a cross-country drive last fall in a trio of Audi TDI vehicles to prove that you don't need to drive extra slow to beat the EPA numbers. In fact, we made it from Los Angeles to New York City in just over 46 hours, cramped but not cranky. We had once again proven that how you drive is hugely important to your fuel usage.
Our latest adventure appeared, at first glance, to be nearly impossible. The EPA says that the Ram 1500 EcoDiesel we would be driving gets just 22 combined mpg (19 city and 27 highway). Gerdes' idea was to drive it as far north from Houston, TX towards Detroit, MI as we could go on one tank. The day before we left, our itinerary got an extra stop. Instead of taking one of the official Shell Eco-marathon prototype vehicles to Detroit, it was decided to bring the winning diesel-powered prototype from the just-finished event to The Henry Ford Museum, where it had been arranged the car would be displayed. The winning car was built by a small team (just four students) from Sullivan High School in Sullivan, IN, who managed to beat a number of college teams with a score of 1,899.32 mpg. That target would be a bit out of reach for the Ram, but could we get 1,000 miles from the tank? Since the truck has a 26 gallon tank (officially, anyway), that would mean the EPA says we could only go 702 miles, assuming all highway driving. Could we make up 300 miles with careful driving? That spells both challenge and fun.
The truck in question was a 2014 Ram 1500 Laramie Limited Edition 4x4 with Crew Cab decked out with all sorts of luxury features to reach a $58,015 price tag. That means it had the customer preferred package that adds a leather-wrapped steering wheel, 20-inch wheels with chrome inserts and a pair of Ramboxes. Most importantly, for our mileage purposes, it had a 3.0-liter V6 EcoDiesel engine with an eight-speed automatic transmission. Gerdes spent some time testing the truck out before we got to Houston for the annual Shell Eco-marathon Americas (Shell was the fuel sponsor for the drive). The drive route was determined, in part, by the fact that the event is moving to Detroit next year, and Gerdes thought it would be a cool idea to drive one of the high-efficiency vehicles from the event's current home to the new home. That also meant that the truck would be loaded down with all of our gear, this wacky prototype vehicle and four people (we were also joined by Keith Griffin ?and Jill Ciminillo?). This would not be a hypermiling challenge that we would meet by stripping out weight.
From his tests, Gerdes discovered there are two ways to get the 1500 to perform at its most efficient. He knows that the trick is to find the zone where the engine is in its highest gear with the vehicle moving at the slowest possible speed before downshifting. Turns out, in the 1500, this is at about 52 miles per hour, depending on circumstances, but it's a narrow band before the powertrain wants to downshift.
So, to keep the truck in eighth gear, there are two options. When going uphill, never let your speed drop below 47-48 mph, because that's roughly where the transmission wants to shift back into seventh gear. If you keep pressure on the pedal and the truck moving at at least that speed, it'll stay in eighth, the most efficient gear. It's hard to do without gunning the engine, but possible. When you're on the flats, you can get up to 55 mph or so and then take your foot off the gas, let the engine go into "fuel cut" (Gerdes' shorthand for deceleration fuel cut off, or DFCO) and then slowly reapply pressure on the pedal. You can see the tachometer drop down to 1,250 rpm as eighth gear is engaged and you know your fuel efficiency just went up. This works because the engine thinks you are trying to get to 62-63 mph where it would normally shift into eighth, and so it does the shift early with DFCO. Gerdes says he estimates there is a 3-4 mpg difference between seventh and eighth gear at any highway speed, so fighting with the transmission for 1,000 miles is worth it.There is a 3-4 mpg difference between seventh and eighth gear at highway speeds.
There's another automatic system in the 1500 that helps with fuel economy that we had to struggle to activate. I'm talking about the automatic aero suspension, which activates when you keep the truck between 62 and 66 mpg for over 20 seconds or drive faster than 66 mph. Once turned on, the system lowers the vehicle by 0.6 inches, making you a bit more slippery as you push aside the air. When you drop below 30 miles per hour (or keep it between 35 and 30 for more than twenty seconds), the auto-aero mode raises the body back up.
The trouble is, getting up to 62 mph meant spending more energy than we wanted, but Ram spokesman Nick Cappa said that the default speeds where the system turns on or off are right for most drivers. "We take into consideration the benefit of the aero dynamics and the comfort of having the extra suspension travel," he said. "It was a long process of study to find the most appropriate numbers. If traffic slows to 35 mph and then speeds back up to 55 mph, we keep the truck in aero so not to over cycle the system, give too much driver input and fully capitalize on the mode. We could have programmed any speed." Ram also didn't want to add a manual override button for aero mode because, he said, "We don't want to limit suspension travel at low speeds in case the driver slows down for construction, bumps or a dirt road" and because "the aero benefit is marginal at lower speeds." So, when necessary, we got up to speed, let the truck drop down and then cruised as best we could at 52 mph or so.The trouble is, getting up to 62 mph meant spending more energy than we wanted.
That's obviously much slower than US highway traffic is used to going, so we used a technique called ridge riding (being a bit off-center in the lane). This has a fuel efficiency benefit on wet roads because the raised center of the lane is a bit dryer than the sides, but on the dry Texas highway, we did this to signal to the semi-truck drivers that we're driving a bit differently than other vehicles. Our bright yellow Shell wrap made us easy to see, and being off-kilter just drew a bit more attention to ourselves. Ironically, that wrap included some of Shell's smarter driving tips, which included "use cruise control." That might help others, but it would have been detrimental for our efforts. We also drove with intention, letting our blinkers flash for a good five seconds before we changed lanes so that drivers around us know we're moving. Yes, some people honked out their anger, but we just kept on trucking and doing our thing.
This included lots of delicious food stops (Lambert's Cafe, home of the throwed rolls, was a highlight) and, finally, our arrival at Sullivan High School early one morning. We arrived just in time for a school assembly, where the mayor declared it to be "Supermileage Team Day" in town. He said the school's victory was what the community was all about and said that, "great things can happen, even here in Sullivan." The kids loved being interviewed by the local media, saying later that they felt like rock stars.
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In the end, here's how our Ram 1500 math worked out. The goal was 1,000 miles on the tank. While the official tank size is 26 gallons, Gerdes was able to pack over 28 gallons in, using a number of tricks (filling it up to the brim by burping all of the air out of the fuel system), so we had around 70 more miles than your average driver would on a 'full' tank. So, 1,000 miles divided by 28 gallons is 35.7 mpg. But wait, there's more. The in-dash display on a Jeep Grand Cherokee Gerdes drove a while back was 2 mpg 'optimistic,' so he assumed the 1500 was about the same. That meant that our target displayed mpg level would be at least 37.7 mpg, Gerdes thought. Not easy.The tricks we used to really get our high mpg numbers are things anyone can do.
When we filled up in Houston (a process that took about two hours, including a Shell photo shoot) the odometer read 2,402 and the the on-board computer said we had 671 miles to empty. Thanks to a lot of careful driving the odometer read 3,443 miles when the "distance to empty" finally changed from 10 miles left to "fuel low." At the point where other drivers would be freaking out, Gerdes stayed calm behind the wheel, confident that his calculations would get us the dozen or so miles to where he knew there was a Shell diesel station. In the end, we drove 1,041 odometer miles and used 27.537 gallons, with the display reading 38.1 mpg. Given the inaccuracy of vehicle odometers, those numbers don't totally equal out, but the point is that we were able to once again destroy the EPA estimates for fuel economy. And we did it with a 1,899-mpg vehicle in the truck bed. One that we safely delivered to an automotive museum in Detroit, where it will sit and inspire more students and green drivers.
Yes, we did things that normal people don't do, but that doesn't really matter for the larger story: you, too, can go more miles per gallon. Because here's the thing: you don't need to fill every air pocket in the fuel system with diesel to hypermile the Ram 1500 EcoDiesel. In fact, it's better if you don't, since the baffles are there to prevent fuel vapors from escaping into the atmosphere. Overfilling is just something Gerdes does to make sure the mpg numbers he reports to the world are absolutely accurate. The tricks we used to really get our high mpg numbers are things anyone can do. The short version is to pay close attention to how you drive and you'll arrive with fuel to spare.
By Sebastian Blanco
See also: Marchionne: Midsize pickup still not in the cards; Ram 1500, Jeep Wrangler could use aluminum, Fiat Chrysler Automobiles: The next five years, Fiat Chrysler Automobiles: The next five years.