Fuel Saving Advice - Aerodynamics and vehicle weight

 

We’ve all seen the advice at different times in the past to clear all unnecessary weight from the car before driving it to save fuel

I remember working in Engineering at Rolls Royce and Bentley, when we used to walk around the prototype cars looking or opportunities to reduce weight. It’s common now, but back then in the early 90’s, the guy who wanted to remove the key lock barrel from passenger doors to lose 50g off the car’s final weight caused quite a debate!

In engineering projects like that of course, lots of little opportunities to save a little bit of weight add up and give measurable gains in performance and fuel economy and the same can be said of motorsport, where they go as far as designing special, thinner profiled nuts and washers made of different materials to save weight in the search for a couple of tenths of a second in lap time improvements – a couple of tenths of a second in F1 terms is a big advantage

Aerodynamics are also vitally important to road car designers and priorities differ between civilian and race applications with race cars using downforce created by the aerodynamics for grip, whereas road cars desire good aerodynamics in the quest to reduce fuel consumption and increase refinement

But once the car is designed and available to buy, being as we’re only wanting to use it travel to and from work and take the kids to the park at weekends, is it really worth worrying about these two things on a day to day basis? Would you notice a difference in your fuel economy if you emptied your boot or closed your windows in favour of pressing the air con button?

As is the case with many things, this is all about considering the percentages and adopting a realistic assessment of what a gain actually looks like

My Ford Focus weighs around 1,400kg when it comes off the production line, I weigh around 110kg and a full tank of petrol weighs around 45kg, so when it drives along the road, the combination of a fully fuelled car plus driver is 1,555kg

When you add another adult and two children (lets say 220kg) and give each passenger a bag of luggage (80kg total), the fully loaded vehicle is around 1,855kg

The difference between the lightly loaded single driver and the fully loaded family going on holiday for the week is around 16%... but do you ever notice any difference in fuel economy when you drive familiar journeys on your own in comparison to being having the full family with you? Neither do I!

Now, those that tow caravans WILL see a difference, and although they probably won’t be using a Ford Focus for this job, if they did, with an average caravan weighing around 1,200kg, that’s adding more than further 65% to the weight of my own fully loaded car, and 85% to the unloaded one - huge differences!

To put this into context, an F1 car will probably be less than 700kg without fuel or driver. If you add 10kg to that, you’re increasing weight by 1.5% and if you did the same thing with my car as it left the production line, it’d be 0.7%

So yes, weight does make a difference but to see gains at the fuel pump, you need to be losing a lot of weight – it’s not worth asking everyone to empty their pockets before getting into the car!

Aerodynamics are also an important part of car design whether it’s road or race cars you’re looking at

A car’s job, aerodynamically speaking, is to firstly punch a hole in the air in front of it and then to let air slip over it easily. Both things mean that the doesn’t have to work so hard to keep speed and momentum. In F1, this means that the car can move faster and grip the road better (F1 cars rely on aerodynamic downforce for grip) and on the road it means lower fuel bills, lower wind noise and a quieter driving experience. In spite of some models having spoilers and things fitted, road cars don’t utilise aerodynamics to create downforce at all really

Consider holding your arm out of the open window whilst being driven…

At speeds that are below 30mph, there is very little feeling of air pushing your arm, at speeds below 20mph, there is almost nothing, but at speeds in excess of 30mph, there is an increasing effect on the pressure applied to your hand and at 70mph, it requires noticeable counterforce from your arm muscles to hold your hand still

You can see from that experiment that air flow over the car is very important and anything that disrupts the smooth passage of the air over the car is adding to your fuel consumption by increasing what’s known as aerodynamic drag

In wind tunnel testing, things like roof racks and roof top boxes add significantly to fuel consumption and there is consistent advice to remove them if you don’t need them, particularly if you regularly drive on faster roads such as motorways

In conclusion, it’s worth thinking about aerodynamics and removing anything that adds unnecessary disruption to the air flow over the vehicle. Wind deflectors stop air from being sucked into the passenger cabin when windows are opened and do a lot to stop buffeting for passengers but I’ve been using them on my cars since covid and can’t demonstrate any fuel economy gains with them

With weight, I really wouldn’t bother worrying about it at all… whether you do or don’t carry that extra 50kg bag in your car, you won’t probably be able to see any difference in your fuel consumption whatsoever

Eco Safe driving, as it’s referred to in the driving test, is a complex subject affected by many, many different factors. Many of the suggestions involve a lot of effort for very little gain that’s often hard to see in the performance of the car due to the constant variables of weather, road and traffic conditions as well as the constantly changing price of fuel

The only way to see whether you’re improving the efficiency of your driving is to fill up until the pump clicks off, and repeat that clicking process three times to ensure that it’s genuinely full and not clicking for some other reason. Then zero your trip computer when you get back into the car and record your mileage when you repeat the process next time you need to fill up again

When you know how many miles you’ve done and how many litres it took to get it back to “three clicks full” again, then you can work out the mileage per gallon by using the following formula and then taking an average over a few readings to get a more accurate idea of fuel economy

Number of miles divided by number of litres = miles per litre

Miles per litre multiplied by 4.546 = miles per gallon

Nick Heath Driver Training helps people of all levels and abilities with their driving. Established in 2005 and based on the South Cheshire / North Staffordshire border in the UK, I can help you to obtain a licence, become a driving instructor, regain your driving confidence or reduce your road risk for work purposes. I am a regular contributor to local and national radio when driving items come up in the news and am willing to contribute to the wider driver training conversation

Anyone wanting more information should call 0800 8 20 2038

Fuel Saving Advice - The Use Of Gears

A few months ago, I took some time out to go out on the road for an hour with an IAM Roadsmart, Masters level driver

For those unfamiliar, the IAM Roadsmart group runs two levels of advanced driving test. The standard advanced driving test that most members have passed, and the masters version, which assess skills over a longer period of time on the road, requires a constantly commentary, takes a more exacting look at habits and needs to be repeated every few years in order to remain valid

Something that immediately caught my eye was the use of the gears and engine rev range

The driver basically changed gear outside his house and didn’t change out of that gear for a very, very long time with speeds reaching 40mph at times without the car being placed into 3^rd

I asked about this and the responsive engine braking is the reason it’s done, allowing a driver more control over the speed with the gas pedal alone, minimising the use of the brakes and of course leading to less wear and tear on the braking system

But what about fuel consumption?

The driver pointed at his trip computer, which showed that he was currently doing 99.9mpg, as most cars do under engine braking, he went on to explain that his car achieved around 45mpg when driven like this, as it spends more time in the engine braking zone than people who need to use the brakes more

Reasonable logic, but completely against the advice of the DVSA, who advocate early changes and considerate block changes as a way of maximising fuel consumption

It's also against advice from the Energy Saving Trust, who advise short shifting and no block changing for fuel efficiency. Their course demonstrates these gains using trip computers

ALL three organisations are in agreement that drivers that look ahead and plan their driving will reduce fuel consumption by eliminating unnecessary acceleration and gear changes

So, over the following weeks I did some experimenting with my own car, in particular with regards to using more rev range and holding back on changing up the gears

What I’ve found is that you don’t use as much fuel as you expect when you drive like that, but I did use more. My car achieved around 50mpg, which is about what it does on an average day’s work with learner drivers at the wheel and 14% below the 57mpg that I expect when I'm driving it

Having said that, from watching the trip computer, I do believe that the driver was right when he said that the car spends more time utilising engine braking but it also seems that just holding a steady speed also gives decent fuel economy, regardless of what gear you’re in

In 4^th gear for example, on the motorway, my car is achieving around 55mpg, which is really close to the 57mpg I'd expect if it was in 6^th with cruise control being used at 70mph (best speed for fuel consumption is always around 50mph). Now I’d estimate that it’s revving a good 1,500 revs higher in 4^th and my expectation was to see fuel consumption drop a lot, lot more than it did

I tried putting them all together on a recent trip to Wales, looking and planning  as far ahead as possible, letting the engine sing when I felt I’d benefit from the extra control provided by the high revs, short changing in free flowing, but heavy traffic where we're just trundling along and then block changing when getting up to the speed limits and cruising… the trip yielded it’s usual 57mph, no different to when I use either of those methods on their own terms

So my advice is to plan your driving, it's the most important side of it. Utilise your gears based on what you can see ahead and how you think your driving plan looks. Plan to hold a steady speed, use engine braking as much as you can and try to eliminate unnecessary gear changes. Don't overly worry about revs, and definitely don't change gear so early that the engine labours - that definitely wasn't good for fuel consumption!

The group, Staffordshire Advanced Riders and Drivers meets at around 715pm on a Thursday evening at Sandyford’s community fire station and they offer a free driving assessment to anyone interested in exploring the world of advanced driving. No appointment is required but you can get more information by contacting their facebook page

Nick Heath Driver Training helps people of all levels and abilities with their driving. Established in 2005 and based on the South Cheshire / North Staffordshire border in the UK, I can help you to obtain a licence, become a driving instructor, regain your driving confidence or reduce your road risk for work purposes. I am a regular contributor to local and national radio when driving items come up in the news and am willing to contribute to the wider driver training conversation

Anyone wanting more information should call 0800 8 20 2038

New Rules Aimed At Making Cyclists Safer

Many road users, regardless of how they’re moving, will be familiar with cyclists openly violating the rules of the Highway Code in passing red traffic lights, sometimes even riding through pedestrian crossings whilst people are walking across them. Whilst cyclists tend to deflect away from this behaviour by talking about how many car drivers you see doing things they shouldn’t, the problem has been growing over recent years as cycling has gained in popularity and the government has recently taken action to address the issue

It was a few years ago when I first read on social media, whilst reading through arguments between cyclists and other road users underneath a video of somebody doing something they shouldn’t, the comment “fun fact, cyclists aren’t governed by the Highway Code, because the road traffic act only applies to mechanically powered vehicles”

I read that with interest because, without being bothered to go and look it up, I was pretty sure that there was at least a note or two of truth in what the contributor was saying – all my dealings with the road traffic act had previously related to motor vehicles

I also noticed that many rules relating to cyclists that the government had, during a consultation exercise in 2022 that I took part in, proposed to be changed to include stronger wording along the lines of “as per other vehicular traffic” had not been modified as such in the final revision of the Highway Code when it was released in February 2023

It turns out that the situation was quite complex and tangled. Some bits of the Road Traffic Act applied and some didn’t. With speed limits for example, the road traffic act didn’t apply, but cyclists could always be charged with dangerous or careless cycling under various laws going back to 1861 with inconsistent success

In order to clear that all up, the incoming Crime and Policing Act 2026, aims to bring cycling into line with other road users with regards to punishments and penalties for breaching the various rules of the road. It received Royal Ascent at the end of April, will be including in the Kings Speech on 13^th May and will become enforceable from 29^th June 2026

That means that cyclists can be prosecuted and banned from driving if they’re caught cycling with a breath alcohol level in excess of the drink drive limit

It means that they can receive a fixed penalty notice for riding through red traffic lights or across pedestrian crossings when they’re being used by pedestrians

In fact, the majority of legally binding rules of the road will apply to cyclists after this modification to the law, with penalties being exactly the same for cyclists as would be applied to a driver of any other vehicle

Hopefully that will mean that we start to see those few (albeit a significant few) cyclists that give the majority a bad name becoming less in numbers now

Cyclists were responsible for 4 pedestrian fatalities and 185 serious injuries in 2023. The figures seem very small in comparison to KSI figures for UK roads in general but it is believed that they are very much the tip of the iceberg and that the relatively low weight, momentum and speed of cycles in comparison to motor vehicles goes a long way towards minimising hospitalisations. The true picture of UK’s roads is believed to include more significant numbers of near misses, minor injuries and complaints and it is this that the government hopes to address with this new legislation 

Nick Heath Driver Training helps people of all levels and abilities with their driving. Established in 2005 and based on the South Cheshire / North Staffordshire border in the UK, I can help you to obtain a licence, become a driving instructor, regain your driving confidence or reduce your road risk for work purposes. I am a regular contributor to local and national radio when driving items come up in the news and am willing to contribute to the wider driver training conversation

Anyone wanting more information should call 0800 8 20 2038

Are graduated licences the next step in road safety?

Graduated licencing (GDL) is the name given to a system of restricting those new to driving in various ways as they go about developing their driving skills and gaining experience.

As such, in a way, you could say that the UK already had GDL, because new drivers must get a provisional driving licence and pass a theory test, followed by a searching practical assessment of their driving skills before being allowed to have a full licence. Further to that, their licence is then covered by the New Driver’s Act, which says that it’ll be revoked (pending a new application for a provisional licence) if they receive 6 or more penalty points within 2yrs of passing their tests.

The news stories you see from time to time are telling you that the DVSA is looking at strengthening these current systems with the aim of further reducing the road risk of new drivers on the roads.

The first proper GDL system was introduced in New Zealand as far back as 1987 and now there are quite a few examples of similar systems in the USA, Canada and Europe, from which the DVSA can draw experience before deciding whether to introduce such a scheme here and what to include in it if it does introduce something.

Common restrictions placed on new drivers include enforcing minimum time periods, mileage or hours of training before allowing somebody to take a test, limiting the number or ages of passengers allowed in the car post test, implementing zero alcohol drink drive limits and not allowing people to drive at night.

Overall, GDL a good thing, but there are a few issues:

Firstly, everyone will be agreed that it really should be a zero alcohol limit for ALL drivers, not just the new ones (I know that for various reasons a zero limit isn’t practical… but a limit that mandates that there is no deliberate drinking done whilst driving is a good thing).

Secondly, whilst restricting the use of the roads at night by new drivers has lead to a 60% reduction in road risk in studies from those countries that introduce such measures, I think something should be introduced that doesn’t interfere with people's ability to be flexible at work.

Many young people are working for hospitality, coffee shops etc and either need to be able to start work early or finish late. They may even work nights. The challenge is to allow them to function economically, whilst addressing that road safety need. In October, Northern Ireland will introduce such a system that mandates new drivers to only drive alone between the hours of 11pm and 6am. I think something like this is the answer.

Without doubt, restricting the age and number of passengers is a good idea. We can see very clearly from crash data that the more passengers that are present in a car, the greater the risk of that car crashing and that risk doesn’t rise in a linear way, it rises exponentially. A single passenger for example, increases road risk by a factor of 2.5 and a 3^rd passenger increases road risk by 4 times over solo driving. The figures show that young men are more affected by passenger presence than ladies but throughout the world, there are no specific restrictions based on road risk for a particular gender.

With regards to fixed terms for learning periods, whether it be a time period, a fixed number of professional lessons or a fixed amount of miles, I think data is a bit skewed in this area for the UK whereas other countries again report positive results from the introduction of the restrictions.

We had to cease lessons completely during covid and obviously some people were already ready for test and had them cancelled due to the lockdown. Then the government allowed people to practice with parents and with quiet roads and not many other excuses to leave the house, a lot of people took up that option. Finally, we were allowed to teach people for about 6wks or so before tests restarted.

The bottom line is that a lot of people taking tests for about 18mths after the first lockdown started, were going into it with 8-10times more driving experience than they would have had before covid… but they weren’t any more successful in taking their tests (not in a meaningful way anyway). The pass rates remained the same, so we have no data of our own to support an introduction of this type of restriction.

One thing I’d like to see is a restriction on how far from home somebody can drive. As I said in my last blog, the driving test was never intended to be passed one day and for that driver to start work as a high mileage, long range driver the next day. It simply doesn’t assess the skills required to do that and with only a small number of people using their driving licences that way, neither should it in my opinion. Maybe a second test that can be taken on unfamiliar roads is the answer if you don’t want to gather gradual experience and need to use the licence for work? I can see no evidence of any country in the world doing anything like that, but it makes total sense to me that road risk must be increased massively on unfamiliar roads and we know from studies that time pressures are a huge factor in driving styles and behaviours.

Nick Heath Driver Training helps people of all levels and abilities with their driving. Established in 2005 and based on the South Cheshire / North Staffordshire border in the UK, I can help you to obtain a licence, become a driving instructor, regain your driving confidence or reduce your road risk for work purposes. I am a regular contributor to local and national radio when driving items come up in the news and am willing to contribute to the wider driver training conversation

Anyone wanting more information should call 0800 8 20 2038

Is the (UK) driving test fit for purpose?

In my line of work, it’s common for people to want to talk about the driving test, how they’d change it (usually either making it harder to pass or making it so bureaucratic that it would become unmanageable) and ultimately whether it’s fit for purpose.

I don’t usually take part too much in these conversations. They bore me to be honest and I don’t like the idea that my generation was allowed to pass a relatively easy driving test and now acts as a gatekeeper trying to deny others the same chances in life.

What do we think the purpose of the driving  test is?

In my eyes, it’s a basic entry level qualification, aimed at allowing novice drivers to demonstrate that they know the rules and that they’re generally safe to drive on the roads so that they can gather experience on their own. It’s not supposed to represent the be all and end all of driving practice and in a perfect world, those passing the test would plan immediately to join their local IAM Roadsmart group and look at raising their driving skills to higher standards… I’ve got to say that addressing the reasons why this doesn’t happen so much is a bigger issue to me than making the driving test harder.

Somebody passing their driving test today, will almost always go straight home and call their insurance company. Once insured, they’ll then go out on one of several journey’s…. pick up some friends, go to the local MaccyD's, go to college, go to the gym or go to work – all of those journey’s are normally about 30mins in length and will usually include local roads.

The driving test of course, is 35-40 minutes in length and includes a mixed variety of local roads and having passed it, the driver has demonstrated that they’re capable of driving in the situations listed above.

Although the cat B licence allows it, the driving test isn’t there to prove that people can start work as delivery drivers running up and down the length and width of the country in massive transit vans with weight limits, height restrictions and time pressures. Nor is it there to give us certainty that somebody is capable of driving 200 miles to Butlins for a stag do with 4 friends in the car, drinking, shouting and bantering each other without mercy.

Within the driving lessons, thanks to European research done in the noughties and the GDE Matrix that came out of that research, we try to discuss these situations and encourage the pupil to talk about how they’d react and deal with them with the aim of at least trying to make it a bit less unfamiliar when it happens… but it is something for which we can’t offer practical experience and people respond to situations differently.

Learner drivers have also receive training in this problem through their school years with regular visits and talks given by emergency services and road safety charities hoping to improve attitudes to the use of the roads.

Overall, I think the current driving test works pretty well myself. It covers 95% of the driving needs of new drivers and in recent years, the DVSA has added more independent driving and a greater focus on parking to it whilst removing examiner input and reducing the amount of manoeuvring and pulling over that is done. They’ve all been good, positive changes in my opinion and I can’t think of ways in which I’d improve it further without appearing to just wanting to stop people moving on in life. I notice that with the New Driver’s Act and the black box insurance deals, it isn’t anywhere near as common as it used to be to see new drivers driving badly after they’ve passed their tests and with the uk’s annual road death’s also dropping, it’s hard to take seriously complaints that it isn’t working.

We should direct our road safety efforts in other directions I think.

Nick Heath Driver Training helps people of all levels and abilities with their driving. Established in 2005 and based on the South Cheshire / North Staffordshire border in the UK, I can help you to obtain a licence, become a driving instructor, regain your driving confidence or reduce your road risk for work purposes. I am a regular contributor to local and national radio when driving items come up in the news and am willing to contribute to the wider driver training conversation

Anyone wanting more information should call 0800 8 20 2038