In Australia the average motorist punches out roughly 18,350kms over the space of 12 months. Just around 350km a week. That’s probably on the low end for most 4X4 owners but let’s work with it for now. You’ll have to excuse us here but we’re going to take a few liberties. It’s important to set a baseline on why little changes are so important when you’re trying to cut down on fuel consumption. If you’re averaging 15L per 100km, also low, you’ll chew through 2,752.5L of fuel in a year; assuming you’re sticking to 350kms a week and not setting off on any 4X4 trips which could easily see you do the same distance in a day.
Now bump the consumption from 15L/100km to 17L/100km, a minor difference, less than most people see just by fitting a few accessories. This will see the fuel usage jump from 2,752.5L up to 3,119.5L, factor in a modest $1.50/L and that’s an increase in fuel usage of $550 straight out of your pocket. Every year. And that’s assuming you drive very little each week. Throw in a couple of trips, or a longer-than-average drive to work, and you could be throwing $1,000 a year in the bin for nothing. Starting to see why this is so important?
But wait, it gets worse. A study done by the NRMA found we import 91% of our fuel. We’d run out in three weeks if the tap was turned off on imports. The flip-side of this is a lot of our fuel comes from countries like Saudi Arabia – one of the biggest fuel exporters in the world. So how do we fix it and cut down on our fuel consumption? (READ THE FULL NRMA REPORT HERE)
Cut the fat
The Environmental Protection Agency (EPA) in the United States did a study a few years back on weight and the effect on fuel consumption.(SEE THEIR LATEST STUDY HERE) The results were for every 50kg of dead weight removed, fuel consumption improved by 1-2%. A seemingly minor number, until we do the maths again. 2% of 3,119.5L is just over 62 litres a year. By pulling 50kg out of your 4X4 you’re essentially getting close to a full tank of fuel, every single year, for free.
50kg sounds like a lot if you’re thinking in terms of concrete bags slapped on the passenger seat… but look at it this way. A second spare tyre will factor in about 30kg, that’s over half a tank a year just to look like you’re off on an adventure, right after you’re done getting some milk from the shops. Add in a few other bits and pieces that don’t need to be on for daily duties, and it’s easy to save two full tanks of fuel a year, just by not driving ‘decked out’ everywhere. Would you rather look like you’re on an adventure, or have the money to actually go on one? Yep, us too, so maybe think about ditching the roof top tent and second spare when you’re travelling around town or on day trips.
The rusty nail principle
Engines use very little fuel per hour sitting on idle, they’re also not overly affected by aerodynamics until over 80km/h. That leaves a whole lot of fuel consumption being soaked up just by pushing the weight of your 4X4 around. Look at it this way. You have 10km to travel, and two different ways you can accomplish this. Option A is to accelerate gently, reach the speed limit and then maintain a constant speed for the whole distance. Option B sees you accelerate a little more aggressively until you reach the speed limit, then you brake smoothly until at a stop, then start again. Stop-start for 10km.
It doesn’t take a rocket scientist to work out which one will chew more fuel. So it goes to say that any deviation from Option A will be somewhere along the scale closer to Option B. Stop-start driving chews fuel due to the increased amount of acceleration, which puts the engine under more load. Sitting in the slow lane along the freeway with your speed rising and falling by 10km/h constantly will chew more fuel than driving at a constant pace. The old saying is ‘drive like there’s a rusty nail sticking through the accelerator pedal’; slow and steady acceleration rather than mashing the go pedal on and off at every opportunity. I think it’d be more apt to say stop-start traffic sucks; don’t cause it for yourself.
Maybe just one case of beer
Right, we’re all on the same page when it comes to excess weight being bad for fuel consumption. If you’re trying to cut back on your fuel bill and buy a few less AK47s for the terrorists, it’s best to leave your second spare at home when you’re not using it. The same can be applied when you actually do need it, though. For most of us, heading off on a trip always feels like an adventure; off to battle the odds, man vs nature, creating fire with nothing but our beards.
Truthfully most of the time we’re little more than a few hours from the nearest 24-hour Woolworths with a Kmart Tyre and Auto right around the corner. If you’re out with a few mates, maybe share the tool kit rather than everyone bringing their own. If you’re doing an overnighter you probably don’t need 80L of water just in case. Everything you need; nothing you don’t.
Maximising aerodynamics
There’s a reason land speed record cars aren’t shaped like shipping containers, and a small percentage of that scales down to the real world too. It’s a bit like a sliding scale, we’re not going the sort of speeds they are so we don’t need to be as slippery; but in the quest for low fuel consumption every little bit adds up. In fact one of the big reasons manufacturers keep canning old style 4X4s is due to poor aerodynamics hurting fuel consumption and (as a result) emissions. With that in mind it doesn’t make a lot of sense to go out of your way to make your four wheel drive less aerodynamic.
That five poster bullbar and 12-inches of lift alone are going to add more than 2L/100km. Near on $1,000 a year for the privilege of looking like you’re fond of your sister. It’s the same principal as knocking speed off on the freeway. The difference between 90 and 110 km/h can mean as much as a 25% saving in fuel consumption, and that’s a lot of rocket-propelled grenades.
The right shoes for the occasion
Grab a bag of concrete and sit it on your shoulders. It’s heavy, but not exactly a feat worthy of YouTube fame. Now get that same bag of concrete, and with the same arms you just picked it up with swing the bag of concrete around your head in a circle. That’s the difference between static weight and rotational weight; and why bigger, heavier tyres aren’t always a good thing.
Increasing the diameter of the wheel is a bit like swinging the bag of concrete in an even bigger arc. Now try and swing that bag of concrete in an arc while you’re underwater. That’s the effect of tyre pressures being too low and an increase in tyre width; more commonly known as ‘rolling resistance’. The actual numbers come down to a lot of different factors; but unless you’re about to compete in a strongman competition this should put a bit of perspective on oversized tyres and their effect on fuel consumption.
Extra fuel
There’s two ways to get a longer fuel range – either decreasing fuel consumption, or increasing the amount of fuel you carry. Long-range fuel tanks are a bit of a mixed bag. They’re a literal necessity if you’re doing long-distance travel, but can also hurt, too.
An average long-range fuel tank can add over 100L to your carrying capacity. With 15L/100km that’d net you an additional 660km before your fuel light comes on. Except you’re now carrying close to an extra 150kg of weight. That’s 3-6 full tanks of fuel a year just to get better fuel range.
Leave them empty when not in use and make the most of them when you need them. They can also help you stock up on fuel when it’s cheaper. An extra 100L of fuel when it’s 25c a litre cheaper can save you $25 in one hit.
All the little things
If you break down what you’re really doing when attempting to save fuel, it all basically comes down to making things easier for your engine. If there’s a way to put less load on your engine it’ll give you improved fuel economy; it’s the basic principle of most diesel tuning chips and their claims of improved fuel economy. It doesn’t all need to be on a large scale though. It’s estimated at speeds under 80km/h, having the air conditioning running can increase fuel consumption by as much as 10%. This is simply due to extra strain on your engine driving an extra pump. Ironically enough, over 80km/h the drag of having your windows down is worse than having your AC on.
You can take this right down to the micro level.
Dirty oil is thicker, meaning an increase in friction and more power required to move. That’s from your engine right through to your diff and even dodgy wheel bearings can affect fuel. Depending on your engine even a dirty or clogged air filter can cause massive restrictions. Each small component may only make a fraction of a percentage of improvement; but over 18,000kms a year it’s money in your pocket, not the bad guys’ pockets.
