Explain this

Jayco-noslide wrote:
My guess is that going down does not cancel up because the motor is still running and using some fuel?

Modern gas (and I assume diesel) engines do not use fuel when engine braking. It's easy enough with computer controlled injectors to not inject any fuel when the RPM is well above idle and the gas pedal is not depressed at all.

Fuel mileage up and down hills should be a bit lower than on the flat because you generally use some braking (of some sort) on the downhill sides, so the energy you put in going up the hill is wasted in braking going down the hill. If you don't brake but use the momentum to go up the next hill, it's a lot closer to even.

Sometimes the difference between hills and flats is not as marked as one would think because the average speed in the hills is lower, and so the air resistance is lower and less energy overall is required for the drive. Slowing down in flat terrain would often result in better mileage, too, up to a point.

Don't forget rolling resistance. A higher inflation should reduce this. We switched from all terrain tires to Dura Grappler Highway and have seen an increase of .4 mpg overall. The 2012 2500 Ram CTD we tow with seems to not really care what's behind it. It always gets ~11 mpg.

My guess is that going down does not cancel up because the motor is still running and using some fuel?

Does the up and down hills vs towing flat improve mileage at all? Im just asking because I pretty much do flat towing now, but I know going "downhill", I can see 20 MPG or more.. of course, going uphill has an opposite effect. The one time I did tow in the GA mountains what when I got my best gas mileage with my previous TV and trailer combo.

Mike

Fuel consumed is almost always going to be most effected by the weight towed and the speed driven, then hills, wind and to a small degree a few other factors. Also, our usual method of checking MPG isn't really very accurate so MPG could vary on paper from time to time even if everything is unchanged.

This is the front design of my trailer quite a bit more aerodynamic that the flat front o the old Spree.

failed picture post

lbrjet wrote:
You may have had favorable winds (or lack there of) on the trip. I can get 7 or 10 on the same route depending on the wind.

We actually had heavy cross winds until we hit Knoxville then it was more of a tail wind the last stretch from Knoxville to Ashville.

Weight impacts fuel mileage most when you are constantly going up and down grades.

Aerodynamics impacts fuel mileage ALL the time.

The 20% increase you describe might be a best case. Looking at pictures/ the design of the two trailers - I'd expect at least 9-12% better fuel mileage.

We joke about getting 15 mpg on a trip to the Rio Grande Valley from Dallas - 7 mpg going down there and 8 mpg coming back. Wind is usually on our nose going down.

I've seen my fuel mileage cut by 30% driving head into a 35 mph wind. Had to be at a specific location at a specific time for a major commitment - otherwise I would have pulled over and waited.

You may have had favorable winds (or lack there of) on the trip. I can get 7 or 10 on the same route depending on the wind.