I was discussing tow vehicle mileage on a race car site the other day and surprisingly learned that even the newset gas powered trucks get crappy mileage when they are towing trailers. Even with the 5 and 6 speed boxes, fuel injection and 35 years of development, most trucks are only in the 11 to 13 mpg range. The guys also have to turn off their lock up converters to make them last. That discussion morphed into things that can be done to improve mileage on new trucks that have all the bells and whistles and a ton of them were applicable to my old beast, so I thought I would share them here and I am going to try to implement some of them myself.

First, there is no way to fool physics. If you are towing an XXXX pound trailer with an XXXX pound truck, you need XXX amount of horsepower/torque/energy to do it. That takes up most of the fuel use. Gearing, driving style andload all come into play and are very hard to change. Therefore, you need to nibble around the edges. The first way is to look at things you can do to reduce the required amount of energy required to move your truck down the road.

Number one is to reduce the weight of the tow vehicle. This means looking at all of the parts of the truck to see what can be reduced in size, shaved or replaced with lighter products. We do this all the time with our racecars, so I am going to start looking at gutting the truck a bit to save weight by removing extra wires, extra bracketry, lighter parts, minimizing wheel and tire weight, lighter seats, etc..... Anything that I can easily do to reduce weight and not impare the functionality of the truck.

Number Two is to reduce frontal area, basically make the brick smaller and more streamlined. Again we do this all the time with our racecars, so the theory is the same, just the method of application. I am going to look at dropping the truck into the weeds and still maintain all of its towing and strength. Don't know how yet, but it is something that can be done. Maybe a set of airbags that I can lower and raise to reflect what I am doing with the truck. I cant find any drop axles for an F250 Supercab, so that may be a bit tough. Also, add a chin spoiler to reduce the amount of air going under the truck and getting bumped along the lumpy bumpy bottom. Fill in as many openings and cracks as possible to reduce the air drag and air reversion points as I can.

Number Three is to put the motor in a sweet spot or happy place at highway towing rpm. I tow at about 60 mph. This translates to about 3000 rpm. I am going to tune the motor to make the most horsepower and torque that I can at that rpm. This will mean a trip to the chassis dyno so that I can validate tuning and a ton of carb changes, but it should allow me to maximize power at that rpm, which should allow me to back off the throttle opening and improve mileage.

Finally, reduce rolling resistance. I am going to look at everything I can do to reduce rolling resistance from adjusting brakes properly, to maximizing tire pressures, to changing lubes and wheel alignments.

All of these things can be done for relatively cheaply and can pay off in better mileage. Right now I get about 9.5 mpg towing with my 460 C6 Supercab. None of these things are out of the ordinary and manufacturers are doing all of these things right now with the newer trucks to maximize mileage.

I will take a baseline next tow weekend, then get started on the work adn see if I can improve the mileage with the work. At the very least, if I can save 1 MPG with this, that turns out to be a 10% improvement in mileage for very little outlay.

Anybody done this already and what did you find?

Regards,

Eric

 

I'm in the midst of a 70 F100 build and am planning some of the same ideas. Helping the cause on the 11 MPG 360FE is Edelbrock's E-Street EFI and a TKO-500 to maybe get 20 mpg. However, weight reduction and aero mods are part of the plan.

In terms of the strategies discussed above, they're spot-on but lemme add or comment:

Aero
Airdam/front spoiler... consider one off an Econoline or fabbing a birdcage frame and fleecing/fiberglassing over it.
The existing grill opening is bigger than it needs to be. A quick way to test is any gains is to apply tape over the unused portions of the grill and seal up the bodygaps with 'racing tape'.

Weight
I'll just say swiss cheese, flared holes, aluminum, and fiberglass.
Lose the dock bumper if you have one. It's about 75 lbs. However, some weight will be regained by using a frame-mounted tow hitch.

Efficiency
Synthetic lubricants if possible to reduce parasitic drag
Tires also have rolling resistance. Consider a narrow footprint and a harder compound.

Higher bucks is to reduce the cruising 3,000 RPM... a Gear Vendor Overdrive seems like a good choice. The payback is quicker if ya drive alot.

Btw, at 10 MPG a gain of 1 MPG "saves" upwards of 40 cents.

 

I can appreciate the thought, but what I read is a whole lot of effort for nothing and/or put yourself further in the hole.

Number 1- Removing unnecessary items is a good idea. Reducing weight and rolling resistance will be an up front cost of probably $1,000 for new wheels and rubber. Replacing stock parts with lighter parts, let's say that's another $1,000 out of your pocket up front. New seats, if you're thinking like something from Corbeau...that's another $1000-1500. So your first round of weight reduction just cost you $3500.

Number 2- Minimum cost for an airbag assist suspension is going to run you $500. So you're running total $4,000

Number 3- All the carb tinkering in the world isn't going to create a true peak sweet spot at that 3k. So let's say another $1,000 in top end parts. Dunno about your area, but a dyno runs $500 for half a day around here. So another $1,500...bringing the total to $5,500.

Number 4- sounds like a good idea...only issue I see with that, you maximize tire pressure, now the centers of your tires are wearing out quicker...and your 40,000 mile tires become useless at 20k.

So the way I see it, you're staring $5,500 in the face for 2 maybe 3 mpg's. So for arguments sake, let's say you gain 3mpg's (which is the high side of hopeful) and lets say gas is $4/gal (and that's overstated too for most of the country) and lets say you drive that vehicle 12,000 mi/yr...you're talking 4.5 years before you break even.

Now lets use the same scenario...but with the 1mpg you're HOPING to get...at a 1mpg improvement, you're talking 11.5 years before you break even.

***Noting if you drive that rig anything less than 12,000 miles a year, ROI will be pushed even further down the road.

In my book, if you're really concerned with mpg's...I think you'd be miles ahead swapping in a gearvendors OD unit or a manual transmission or swapping in a modern diesel/tranny. I'm not trying to persuade you from trying, but I'm a finance guy, and those numbers tell me there's a whole lotta work for not much return. But for all I know, you might pick up 10mpg's and already have any necessary parts on hand.

 

Never thought of the dock bumper. I have one and a chassis hitch setup. Off it goes and save a ton of weight right away.

Great to see someone else is trying this.

Eric

 

WOW, I don't know about your pricing. I can buy cheap Chinese Corbeau knock offs for about $150 each new up here. I can also purchase used racing buckets for around $100 each. Wheels and tires, just bought them and they are going to stay on the truck for a while and I am just going to bump up the pressures to maximum recommended. Your $3500 goes down to about $300. I can cut and swiss cheese stuff for very little as I already have the tools and knowledge from running my race cars.

If I go with an airbag set up, I expect it to be about $500, but I may just chop the front coils some more, like the truck used to run. My I Beams were bent to allow for reduced ride height and proper alignment. I raised it up when I bought the truck with new coils and have about 5 degrees of positive camber. I can add another 1" shim between the rear axle and diff for about $50. Total is now $350.

Dyno time where you are is pretty expensive. I can do 3 pulls on a local dynojet that I use for my racecars for $80. Lets say I run 6 pulls to tune it with the O2 sensor hooked up. That takes me up to $510. Add in all of the other bits and pieces to make the front chin spoiler, the side skirts like tractor trailers run and all the lubes I need. Lets be generous and say that I run a total of $300 in bits and pieces. That takes me to a total of just over $800.

If I can pull an additional MPG out of this and if we can use $.40 as a bench mark, it will pay for itself in 2000 miles and anything after that is gravy. Later if I want to drop $ 4000 for a Gear Vendors OD, I can. I only tow with my truck about 10 times a year and the rest of the time it sits there waiting to go again, so its not worth it for me to drop a ton of coin into the truck, but I do go crazy thinking about the 10 mpg when I am towing especially when I can do something about it.

Eric

 

I have found the cheap "race seats" give real quick, and overall are kinda crappy. a buddy of mine had a set in his honda, within 6 months they were shot. I know its not an every day driver, but as a big guy (6'2, 270ish) I can tell you they were the least comfortable thing I have ever sat in. That being said, I think he shaved close to 50 lbs doing that and got his honda in the 16's (lol)

 

-Well...I'm the kind of guy if I have a rig I plan on keeping, I'm not using crappy chinese parts. So you have me on the seats. Hell...if you really want to reduce weight, go ahead and just ride around on an orange crate or folding lawn chair.

-The tires are matter of timing semantics, you bought them already...so that goes in to the cost. I can build a $500 557 stroker too, as long as I start counting cost after I've almost buttoned up the engine.

-And you also said you were buying lighter parts...I assumed that meant you were going aluminum or fiberglass where stock would have been steel or cast iron. IE fiberglass fenders, aluminum carb/intake, etc.

Well...you were the one that said airbags...kinda tough to budget for a project if you don't even know what you want.

An afternoon means an afternoon, unlimited pulls on the dyno for $500...doesn't sound too terrible to me. But like I said, ONLY tinkering with the carb (like you said) isn't going to maximize power at your tow speed.

Like I said...not trying to persuade you one way or the other...I just assumed you meant you were planning on a quality build. I really think you're underestimating though, even with your figures. But good luck man. For your purpose, it might be more time/cost effective to just go with a gear swap.

 

If it is being used for towing I would suggust against cutting a bunch of holes in it. Its still a street car. Plus if you are towing that adds a bunch of frame stress. Fiberglass panels would be a better way to go

 

Google "Tom Ogle" and "US Patent # 4,177,779"

 

Smokey Yunick applied the same principle to a Pontiac Fiero.

 

As an engineering student, I would like to say that is probably the biggest load of bs...then again I've never tried it