How come I get better MPG's when towing.

Yes you read it right.. My mileage increases when towing.

For the last year I have been keeping tabs on my mileage the same way. So I know it is accurate. The most I have gotten was 13.4. This past week I towed two trailers, one 26 and one 32 feet. Both were about 35 miles one way and the on the way back unloaded. At the end of the tank, I filled up.

I punched all the numbers into my spread sheets, and lo and behold I got 14.1 mpg. That is a record high for me in this truck. Even with freeway trips.

How in the hell can the mileage improve? I think the OD is too low and the engine lugs on the freeway. Would that make sense?

 

How much are you towing? How fast do you drive towing vs not towing?

 

Trailers were I would guess 5000, and 7500#. I normally drive 65 and with the trailers I went 65 also, but it took a whole lot more throttle to get me there.

 

I got a few ways to explain how you got your results, but the first thing I want to mention is I don't beleive them.

I don't think two short trips of 35 miles with loaded and unloaded trailers is enough data to make a good math based conclusion. I would want a few hundred miles.

But lets play "devil's advocate" for a second and I could still think of how it could happen. Were the trips full trailer down hill and empty trailer uphill (on average), the gas saved by being pushed downhill did not ofset the extra gas burned pulling empty uphill. Whether you were aware of it are not you WOULD drive different on and off the trottle with a trailer than without. Maybe your driving style without a trailer is wide open style that burns a lot of gas, your "hey I'm pulling a load so watch the braking and traffic and merging" styyle saves more gas inspite of the load. I other words you were happy to ride behind the slower guy in front of you because you were pulling a trailer and didn't want to be crazy, were normally you would have gunned it and passed.

Man I don't know why you got those numbers you did. But you asked and I thought of a few answers. Think about your driving styles and see if it adds up. Also I would want some more data before I started towing 5000lbs to work every morning to save on my gas bill, LOL!

 

Well, I'm not sure about the "lugging" theory. If you are running around 1800 RPM at 65 mph, then I would not quite call that "lugging".

Also, Soilman makes some excellent points about driving style and driving distance. For myself, I want at least three half-tank runs before I reach a conclusion about impact on mileage, and truly, I would also want to see the same "improvement relationship" for "highway", "city", and "mixed" driving conditions.... again, ideally, three half-tanks for each style of driving.

 

I guess I agree with all of you, except the fact I have calculated my mileage the same way for nine months. So I know it seems crazy, but there is no way it could be wrong. I fill up and divide the miles driven by the gallons put in. I do it the same EVERY time.

I did tend to stay behind the people that were going the speed limit. But I was not going under 60, and it took a lot more throttle to stay at 65 than it normally would. So I know it was not because I was poking in the emergency lane at 40mph. Even if I was, the sheer added weight would be enough to make me lose MPG's.

I guess what I am saying is all things point to my gaining MPG's. I only drove on 1/4 of the tank when towing. It was never downhill and the wind was NOT in my favor believe me. THe rest of the 3/4 of a tank was my normal driving habits, city, stop and go, highway.

I expected to lose MPG's regardless when towing anything, not gain them.

 

Well you know it should not be the case so slow down and look for the answer. Something you did was different during those tanks of gas that offset the fact that you pulled a trailer some during those tanks of gas. If you fiqure out what it was then you should be able to save more gas when you aren't pulling a trailer, get my drift!

 

In the immortal words of Foghorn Leghorn, "You must have done something wrong, son."

 

I'm gonna have to slap you around son. When I tow I am lucky if I only loose a couple mpg.

Wild Wild guess is maybe your tow rig is tilting your truck so the tanks take a bit more gas than usual and when you fill up later without the trailer(so the truck is level) maybe it takes less gas than you actually used.

Got me, this is weird and very counter intuitive.

Jim Henderson

 

Truck had a full tank when I started towing the second trailer, I towed it 35 miles and unhooked, still on full, Drove the truck empty back to work (35 miles) and parked it. Was down to 3/4. Drove it the rest of the day, the next day and half the weekend, filled up. Got my mileage numbers.

Soilman, you have 200K on a stock 5.4? Any issues?

 

That's a long story about my engine. I never said it was stock. It now has 223,000 miles and is starting to go away on me, no oil pressure at idle and the bottom crank sounds like a PSD but I have used it very rough. I started using it like it was paid for long before it was and it just got worst once it finally was paid for, LOL. The 25,000 miles have been with the rev limiter turned off and being used for a comp mud bog truck. I am accually going to try my best to finish it off this weekend at the last mud bog of the season. I will make four hard runs with it and give it hell the whole way. I want a good engine like this one to die a samuri's death and not just lock up going down the interstate, LOL!!

 

I guess you could check to see if your engine is lugging by driving around on your next tank with the OD off, to see if it improves mileage.

One other thing, maybe the towing blew some of the accumulated crud out of your engine so it runs better? I've known this to work with diesels, but I guess it could happen with a gas engine.

 

Lugging could be an issue but at 65mph I doubt it. How much in town vs. highway driving do you normally average? Maybe these trips with trailers and back empty was enough pure highway miles to up your average. Have you tried making the same trip, the same number of times unloaded for comparison purposes? Did you fill up at a different spot than normal where the pump may have a different cut off level?

 

All of these could be true. But with the way I was driving the truck I would expect the mileage to drop significantly, not stay the same or go up.

 

Okay, only one way to really test this, and put it to sleep. Just keep the trailers hooked up for a couple of tanks of gas. In other words, when you're done with your haulin', don't unhook the trailers. Just keep 'em hooked up and drive your normal driving. Do that for a couple of tanks of gas and then crunch the numbers again. Try it with each trailer. If you continue to get better mileage with a trailer hooked up, heck, I'd just leave it there. Find a bigger parking place!!