Hypermiling a Ram 1500 EcoDiesel to 38.1 mpg | Harold Zeigler Newsletter Kalamazoo MI
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Date posted: June 2, 2014

Hypermiling a Ram 1500 EcoDiesel to 38.1 mpg

You never quite know what Wayne Gerdes has up his sleeve. The man who coined the term hypermiling is always looking for adventurous ways to prove that anyone – even you… yes, you – can eke out more miles per gallon just by changing the way you drive. Saying that is easy. Proving it by going on outlandish cross-country drives is hard. But for Gerdes and his team of fuel economy fiends over at CleanMPG, hard is half the fun.

Our latest adventure appeared, at first glance, to be nearly impossible.

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.

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 4×4 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.

There is a 3-4 mpg difference between seventh and eighth gear at highway speeds.

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’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.

Source: [AutoBlog.com]

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