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Car Economy tips - One

Here is a quick rundown of what's on this page:

1. Check the pressure
2. Keep it Serviced.
3. Take that Roof Rack off
4. Shut that Window
5. Turn the Air Conditioner off

Check the pressure

All I'm asking you to do is one little thing:

Every time you fill up at the pump, will you do me a favour and check the tyre pressure?

One of those little bits of resistance I described in "The Basics" is the resistance of the road. The parts of the vehicle that are in contact with the road are the tyres. Now tyres don't normally over-inflate themselves but they do lose pressure with time and this has two effects:

1. Firstly: if the tyre is too soft than the rolling resistance increases, with the side effect that the tyre will wear more quickly and in particular the sidewalls will get damaged.
2. Secondly: you can be pretty sure that the tyres will not lose their pressure equally all the way round and tyres with different pressures will make the vehicle wander or "crab" down the road. This is obviously going to be exaggerated if the front tyre is the soft one. All that effort in keeping the car in a straight line is going to make the resistance caused by the tyre on the road that much greater.

OK - I hear what you are thinking: "Surely this is not going to save much fuel?"

Of course you are right, we are not talking major savings here but I wanted to break you in gently!! However the saving over time by checking your tyre pressure every time you fill up at the pump will be significant at the end of the year. It's cost you NOTHING.

Did I say Not Major? The extra cost of running on badly under-inflated tyres can be up to 5%. I know you will never let the tyre pressure get that bad (oh yeah!) but just a few psi can make a difference to your fuel bill.

You remember what I said about the "State of Mind" I wanted to create in you? Well this is the first tiny change. Just do it as a favour to me, c'mon - it's easy!

There is a secondary saving here - your tyres will last longer.

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Keep it Serviced.

Here's another really easy one: don't make false savings by skimping or missing services.

The engine itself, and all the bearings and gears, steering etc. all need lubrication for smooth running. Smooth running is easy, friction-free running. So you need to attend to this constantly.

Do you know that oil breaks down with use? For a start it's important to use oil of the correct viscosity so follow the manufacturers instructions. However as the oil gets thrashed around and beaten up in the engine and the gearbox it starts to break down and the molecules become less able to act as a cushion between the metals at those metal on metal movements. Technically: the Viscosity is degrading. The metals start to impact one on the other, in other words start to wear, and friction starts to increase.

How often is the interval between oil changes for your car? For a lot of modern cars now the manufacturers say a year or 10,000/12,000 miles. That's a LOT of miles and a lot of crushing, thrashing and beating up for the oil.

So maybe the oils are getting better too. I'm sure they are, but what I recommend is:

Change your oil every 6000miles and always change your oil filter too.

Personally I do this myself - the oil change that is - with my Ford Focus and it's the devil's own job to get at the oil filter when you are lying on your back under the engine and bits of muck are falling in your eyes. It's one of those 5-minute jobs that usually takes all morning, but I don't need to take it to a garage or pay for an "engineer" to get it done.

However when it comes to the rest of the servicing that needs to be done then I don't mind paying for an expert and you shouldn't either. If the engine is running well, if the wheel bearings are running freely, if the brakes aren't binding, if the timing isn't "off", if the engine temperature is OK, if.... - then you are more likely to be getting the most out of your fuel.

Make sure the wheels are balanced and the tracking is checked next time you get new tyres. I know there's an extra charge for this at a lot of places but if the wheels and tyres are running true then the resistance on the road is minimised.

Now one more, really important tip while we are talking about servicing:

Check your Air Filter regularly and change the element if required

The ignition and efficient burning of the fuel depends on a good supply of Oxygen and the whole system requires that the right amount of Oxygen be supplied to the inlet manifold. If the filter is blocked then you get inefficient burning, lack of power from the engine. Incomplete combustion also means worse emissions from the exhaust. With my Ford Focus the recommended interval for changing the Air Filter is 30000 miles. This may seem a long time and it's always worth checking the element between times. Sooty or oily deposits mean a replacement is due. If it's just dusty then it can be re-used by blowing it clean. If it's a paper element it cannot be washed. Some filter elements can be washed or re-oiled but check the manual for your vehicle.

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Take that Roof Rack off

Have you got a roof rack on your car?

The resistance of the passage of the vehicle through the air is a major factor in the amount of fuel consumed.

You can try this out yourself - carefully!! Next time you are out in the car, open the window and stick your hand out. At 30mph it might be quite bearable but try it at 50mph or 70mph next time you're on a motorway. The turbulence and the effort needed to keep your hand still is quite something.

I've done quite a bit of sailing and when even a force 5 breeze -around 20 TO 24 MPH - drives spray in your face it's pretty painful. A true gale is about double that and it's getting hard to stand up, a hurricane is classified as a wind of over 74mph and it's not something you want to be experiencing. Now think in those terms when you are dashing along the motorway at that speed.

The manufacturers spend a lot of time in wind tunnels - or at least their cars and models do - to get an efficient shape so that the car can slip through the air effortlessly. They are trying to reduce DRAG - a combination of aerodynamic or hydrodynamic forces that tends to reduce speed. They spend millions on the problem. Drag is one of those things that, when looked at from a mathematicians' or engineers' point of view, is dependent upon the square of the velocity, which is why it gets more of a problem at higher speeds.

Can you guess what your roof rack does? Apart from nullifying the manufacturers millions, it's making it much more difficult to drive the car through the air.

Result - higher fuel consumption. Even if you have bare bars with no load you could be using 2 or 3% more fuel. If you load on a roof box, even one of those aerodynamic shaped ones, or perhaps some of those devices I see to carry cycles on the roof or a couple of ladders then you are wasting much, much more.

So the tip is:

Take those roof racks off.

How long does it take to remove the rack and save a lot of your hard earned cash? How often do you really need those racks?

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Shut that Window

While we are on the topic of Drag, one of the side effects of doing something as simple as opening the window while you are driving is to increase drag and influence your fuel consumption adversely.

Again it's worse at higher speeds, the turbulence experienced if you drive at high speed on a motorway with the windows open is such that normal conversation becomes impossible. This turbulence is creating an invisible envelope of disturbed air around the car and increasing drag.

Funnily enough this turbulence is a good thing because when the noise from the window becomes too much, such that you cannot hear the radio, you shut the window.

So this tip is:

Shut that Window

However there is more to this than first meets the eye!

As I pointed out earlier the motor manufacturers are spending fortunes on their study of car aerodynamics. Because modern cars are more streamlined and aerodynamically efficient, the drag created by opening the window is proportionately more than if the car is an older, less aerodynamic design. If your car is a "boxy" design then opening the window at low speed is unlikely to cause a large increase in your fuel consumption, whereas if you drive a streamlined arrow then the increase will be larger as a proportion of that car's base aerodynamic efficiency.

So what we have is a more complicated set of alternative scenarios:

1. If you drive a box then at low speeds having a window open is going to have little effect.
2. If you drive a box then as your speed increases your drag goes up and your fuel consumption will rise, so shut the window.
3. If you drive a streamline model then having a window open, even at lower speeds, will have a greater effect proportionately on your fuel consumption.
4. Then if you drive your streamlined model at higher speeds with the windows down then you have undone all the work the manufacturers and their engineers have put into the design and your fuel consumption will soar.

However (isn't there always a however!!) another factor must be considered which brings us to the next point:

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Turn the Air Conditioner off

The big debate: Open the window or turn the A/C on??

There have been many arguments about the effect on your fuel consumption of having your air-conditioning running. Some people say that the extra horsepower needed to turn the compressor over is using more fuel - they are correct. Some people say that the effect is highly exaggerated - I suspect they're correct too!!

Let me give you my take on this:

The engine is certainly working harder if the compressor is being driven - in the same way as the effort required to climb a hill is making the engine work harder. The difficulty I have found is to get hold of the figures to prove how much fuel is being consumed. I have found one figure, which quotes 2.5miles per gallon that, instinctively, sounds an awful lot!

Someone else did a self-test with these results:

• Windows up, AC off: 35 MPG
• Windows up, AC on: 34.4 MPG
• Windows down (all four), AC off: 33.8 MPG

In other words not a huge effect, but a difference all the same.

The Florida Solar Energy Center found a different result; when they tested a Volkswagen GTI they found that at 108KPH:

• Fuel consumption increased by 3% with the windows down but
• by 12% with the Air conditioning running.

Mind you this test was carried out in Florida in July!!

Now of course I'm assuming that you are not running around with the Air Conditioning turned on AND the windows open. That's like trying to cool down the weather!

So you've got to ask the question: Where does this leave us?

Both Air Conditioning and opening windows affect the fuel consumption in detrimental way. The effect of opening the windows gets worse the higher the speed and the more aerodynamic the car's design. I suspect, but without any proof, that the horsepower lost by the demand of the Air Conditioning Compressor is less of a problem when the engine is revving faster, i.e. at higher speeds, than pootling around town.

So my advice to you is this:

Open your window at low speeds around town but shut them on the motorway

And

If you must have the Air Conditioning on then the motorway is OK

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OK That's enough for now. To get some more tips just click here.