A Guide to Getting the Most From a Gallon of Liquid GOLD

Author: Jim Allen
Photos: Jim Allen

“Jim! Jim, are you there? Jim!” Those were the first words I heard upon regaining consciousness. I jolted up in my office chair and retrieved the phone to finish the call with Denis Snow, our illustrious editor.

“What did you just say,” I asked?

“I said that gas is up to $3 a gallon here in Southern California.” My vision blurred again and went dark around the edges, but somehow I managed to stay conscious.

You can have more power with more economy if you pick the rith products and apply fuel saving driving techniques.

“That’s obscene,” I replied! “It’s un-American! It’s unbelievable! It’s Bovine Scatology!” It’s all of that and more... It’s also reality.

I’m not quite into the doddering old man category, but I remember having to cram $5 worth of Chevron 102 octane high test into my old muscle car back in the late ’60s to fill it up for a weekend of tire-smokin’ fun. Having paid as low as 22 cents a gallon for regular in my life, these new gas prices occasionally give my heart an involuntary stress test.

Part 1- The Human Factor
Once you’ve dealt with the outrageous reality of having to pay so much for gasoline or diesel, the question becomes what you can do to stretch those half-a-paycheck fillups a little farther. I’m happy to say that there are a number of free and almost free ways to do that. There is a cost in the personal self control area, but then you can look at this as a new type of challenge. Call it, “Zen and the Art of a Light Foot on the Gas Pedal.”

The biggest impact on your mileage comes from improving the connection between your brain and your right boot. You can add 2-3 city mpg by following the tips below and perhaps 2-5 on the highway. If your rig is getting 10 mpg, gaining 2 mpg is like getting an extra 40 miles out of a 20 gallon tank and saving 4 gallons. At 3 bucks a gallon, that’s 12 bucks.

Egg on Your Foot
Way back when, they used to have us imagining accelerating like there was a raw egg between your foot and the gas pedal. Get too rambunctious and that egg ends up all over your foot. Accelerate moderately.

Shifting Gears
The goal is to keep the rpms relatively low and get the vehicle into the higher gears as soon as possible without lugging the engine. Keep the rpms in the most efficient range at or slightly below peak torque.

Use The Force Luke!
That force is called momentum and it can be used many ways in many situations. Once you have accelerated to speed, look at that speed as money in the bank. You’ve spent the fuel to get up there, don’t waste it by slowing down or stopping needlessly and then have to spend that fuel again. You’ll use the most fuel at lower speeds getting from zero to 10 mph, so staying above 10 mph will really help. Obviously you have to use common sense putting this into practice Another worthwhile use of The Force is on hilly terrain. On a downhill, back off the throttle as much as possible while maintaining your speed. If you are coasting down one hill to climb another one, build up a little extra speed so you will use less fuel on the climb.

Reading Lines... On the Street
Watch the road ahead for stopped or slowing cars, red lights, yellow lights or stale green lights. If you see a slowdown ahead, drop your speed to let the traffic clear or the light change before you get there and have to slow down a lot, or stop.

Speed Sucks
Yeah, it sucks fuel. Believe it or not, most rigs deliver the best fuel economy at around 40 mph. At this speed, air resistance is relatively low but it goes up dramatically the faster you go. It takes about 30 hp to drive the average stock rig at 40 mph, increasing speed to 45 mph can increase air resistance enough to draw 40 hp, about a 34 percent increase in power required for a 10 percent increase in speed. Jumping from 40 to 65 mph can make horsepower requirement jump 310 percent, to 125hp. According to some studies, an average car at freeway speed can increase fuel economy approximately six percent for every five mph slower it’s driven. It might be more for the average built 4x4, given their atrocious lack of aerodynamics.

Use the Cruise
Many newer rigs have cruise control. Use it. Some studies have noted a one to two mpg difference between using cruise control and not. That isn’t to say that a focused person can’t equal cruise control, but over long periods the person gets tired. Cruise doesn’t.

Dynamic Warmups
An idling engine is wasting fuel. A cold engine idling uses more fuel than a warm one. On a cold day, start it, idle just long enough to make sure the oil pressure comes up and drive away, driving slowly at first to warm it gently. That assumes that the windows have been safely cleared of ice. The engine warms up faster this way and you are using the fuel for work rather than just to warm the engine. This is especially important for diesels, by the way. They generate very little heat idling. If you have a diesel, most likely it will have a block heater. Use it! It will save fuel by having the engine partway warmed up upon first start. It will start more easily too.

Being Cool
Some tests done in the ’80s showed that running with the windows open cost about 1 mpg on a test car due to loss of aerodynamics. Using the A/C, especially at low speeds around town, cost 2 mpg on the same car. At freeway speeds it cost about .5 mpg. On most 4x4s, given their poor aerodynamics, I doubt the window thing will be much of a factor. The A/C might be another deal.

Part 2- Vehicle Factors
Many of the things we like as four-wheelers costs fuel economy. To start with, most 4x4s have the aerodynamic characteristics of a house. Big tires increase rolling resistance and reduce aerodynamics. Lifts reduce aerodynamics even more, as does all the hardware we hang all over. Many of the performance mods we add cost MPG. Low gears wind the engines up and cost fuel. All that extra weight makes the engine have to work harder and use more fuel. From the MPG standpoint, almost everything we do is shooting us in the foot. Still there are a few things we can do to get back some of what’s lost.

Tuning Tools
You can improve every rig with a few simple tuning tips. How much you gain with each individual tip might be unmeasureable, but if you add them up, you could pick up an extra MPG or two.

Tires- Highways tires generate less rolling resistance than all terrains. All terrains generate less than mudders. A less aggressive mudder will generate less than a very gnarly one. A hard rubber compound creates less friction than a soft one. All that said, airing up whichever tire you have will decrease rolling resistance. Running the tires at or near the maximum pressure on the sidewall can decrease rolling resistance and offer slight gains in MPG.

Engine- Keep your engine in a good state of tune. Four wheelers end up with dirty air filters more often than other drivers, and this is a big gas waster. Use fuel saving oil. If your engine requires 5W-30, use it. If you can use 10W-30 rather than 10W-40, do so. Heavier oil than you need increases frictional losses inside the engine. Using a more slippery oil, perhaps a synthetic, or a friction reducing additive, can reduce frictional losses even more. If your engine has adjustable ignition timing, advancing timing 1-4 degrees can offer a bit of extra MPG. If the engine pings, of course, you’ll have to turn it back it until it stops.

Drivetrain- Going to more slippery oils in your drivetrain can make a huge difference. I once watched a dyno demonstration where a four-wheel drive was tested with regular gear oil in the t-case and diffs. The gear oil was changed and some friction modifiers from BG Industries were added. With no other changes, a 15 hp again was realized at the wheels. If you have locking hubs, keep them unlocked. If you have a rig with a CAD (Center Axle Disconnect), consider going to a locking hub conversion to reduce internal axle friction. Some owners that have done so report an honest 1 MPG increase. For those in cooler or winter climates, going to a multigrade gear oil (75W-90) can decrease drivetrain friction considerably on cold mornings. Ditto going to synthetic gear oil.

MPG Monitors
Some new rigs have trip computers aboard that will monitor and calculate fuel economy as you drive. There are some aftermarket trip computers that can be installed on most any vehicle. This is the ultimate way to adjust your driving for maximum fuel economy. Even the old standby, a vacuum gauge (only works on gas engines because diesels have almost no vacuum), will work. Simply keeping the vacuum as high as possible as you drive will give you an indicator that you are getting the best possible mileage.

Fuel is a Tool
Gasoline- You may get slightly different mileage from one brand of fuel versus another. One study in the 1980s indicated that fuel density (the amount of energy, or BTUs, in the fuel) varied as much as 4-8 percent between different brands. In theory, that could effect mileage by the same amount. No, I can’t tell you which is good and which is bad, but if you’re accurately and consistently checking your mileage, switch brands and notice a change, there you go. And before you ask, going to premium won’t offer any mileage increase if your engine was designed for regular. Using regular in an engine designed for premium, however, might cost bit of economy... besides the pinging that will ensue.

Diesel- Diesel owners may notice a boost in economy by using a true premium fuel, or a cetane booster. A higher cetane rating produces more power and the result is that you get more work done with the same amount of fuel. Dyno tests I did back in the ’90s on my 6.2L GM diesel showed that going from a fuel that was approximately 40 cetane to 45 cetane fuel (via an additive called Stanadyne Power Formula) was worth 9 hp. The thing you have to watch for is that there are no Federally mandated standards for what can be called “premium” diesel. Most diesel fuel is about 38-42 cetane... most of it at the low end. The industry generally considers 46 cetane and above as premium fuel, but the fuel manufacturers can call anything “premium” out there in the fuel pumps. Overall, the best mileage will be obtained with summer grade, #2 diesel. You will see a big mileage (and power) drop with #1 diesel, or with winter blended diesel (a mix of #1 and #2). Going back to the cetane booster, the increase in mileage may or may not be enough to make the additive worthwhile financially.

Drive Something Else
Some people use a cheap economy car for an everyday beater and save their 4x4s for the times that count. When you consider wear and tear on your rig as well as fuel costs, you might be able to make something like that work financially. I’ve known a couple of people who wore out a gnarly $600 set of trail tires every year driving to work. Cars are usually pretty cheap, but insurance for another car can really eat up the bucks...especially for the young guys still in the insurance industries’ “testosterone crazed” high risk categories.

Engine Modifications
Most people don’t modify an engine only for increase economy. In many cases, however, mods will give you an increase in both power and economy. The thing to remember, however, is that the power increases are there for a reason and it’s often hard not to use that power... especially during the honeymoon period right after the mods. Part of how an increase in power gives you mileage is that you have to use less throttle to get the job done. The stuff listed below is very general but you will be able to get the gist of it.

Beware of the “as advertised on TV” fuel saving gimmicks. Most don’t work, and those that do offer such marginal gains that you’ll probably be dead before you recover the cost in fuel savings. Every once in a while an independent testing facility will put these items to the test, and they usually fail miserably.

With the right engine mods, it’s pretty easy to pick up 1-3 mpg. That will not be cheap mileage, since those parts will cost you, but if your goal is also extra power (when you choose to use it), then you can feel more justified in the expenditure. The biggest increase I’ve ever personally seen and verified on a V8 was 5 mpg. It was a full-sized late ‘70s Ford LTD sedan with a 400ci 2-bbl that went from about 15 to 20 mpg.