Why 60 mph is the best speed for the motorway
This article will be slightly different from the others that I have written, it’s the cost of living crisis and here is a way that you can save money on your commute when driving. Commuters hours generally means roads are busier and below I have stated some changes you can make to save some money.
I have always been called an old man when it comes to driving but I do to save money in comparison. It also means when going on longer journeys with friends fuel prices are significantly cheaper. If you don’t drive this won’t be for you but if you do have a look and see if it changes your attitude when driving.
MPG
Firstly let us define MPG. It’s confusing but in the UK we buy our fuel in Litres, but the most common way to describe efficiency is miles per gallon. In Europe they like to use L/100km but this is confusing unless you use metres and not miles to define your journeys. This confusion makes it harder to actually quantify how much fuel you actually use in a journey, in a ideal world as miles would probably never get scrapped L/100,10 or 50 miles would actually be a better measure for the UK.
Every UK Gallon is approximately 4.5 litres of fuel.
The easiest way that I usually do any conversion when looking at how much more efficient a certain MPG is than another is to compare it to a full tank. Most cars on average will fuel up around 10 gallons of fuel, so for every number increase you get, multiply that difference by roughly 10 and thats the extra range in miles you will achieve. Change in driving style that increases your MPG by around 5 will net you a 50 extra miles in fuel.
Time:
So the biggest reason in which people prefer to drive at 70mph or over is savings in time but what if I told you that you actually don’t save that much time and it also causes you to use more fuel. Hang on let me explain.
Lets say your commute is 20 miles of motorway driving (Key distinction: I will clarify after this)
This is how long it takes, if roads are empty and you have cruise control on.
60 mph: 20 minutes
65 mph: 18.4 minutes
70 mph: 17.1 minutes
75 mph: 16 minutes
I say motorway driving because when you actually look at the whole journey, there will be a portion of the journey getting to and off the motorway in which you travel way slower, this portion of your journey will be so much more significant to the total time than the motorway portion, most of the time.
For example getting to the motorway, if there are loads of traffic lights in your route this will give the most variance to the actual time it takes to make it there. Or one of those annoying 3–4 way traffic lights they put up when they are doing road works, they can easily add a few minutes to your journey.
Average Speed
However I am sure that most of you who do drive at 70mph will know that, there are various reasons in which you will have to change your speed. And if you didn’t notice that, the next time you drive keep a mental note.
Firstly there are a couple main things which eat your fuel inhigh amounts:
Accelerating: Staying at a single speed decreases the amount of fuel used, accelerating uses the most fuel in a car. (Accelerating requires you to increase your RPM)
Overtaking: Most people will go over 70 mph to overtake cars at close to 70mph, no-one really does slow overtakes. Cars are their least efficient over 60 miles an hour and get even more inefficient over 70 mphs. That compounded with the fact that you have to accelerate to reach that speed.
Lets say you are on a 3 lane motorway. If you are travelling at 70 mph it’s hard to stay in the left lane for larger amounts of time. This effectively means you only have 2 lanes. You are also going faster than most cars on the road and if someone is driving slower than you, you will have to slow down before you can overtake or even worse hit the breaks.
This also means if for any reason you have to slow down, you then have to accelerate again to 70mph. If someone is in-front of you at 68 mph you will then overtake and go even quicker than 70 mph in most cases.
This requires you to overtake more and the average speed that you travel at will absolutely be below your target, 70. Which is largely ironic as the journey time will be closer to that of 60mph.
The next time you are on the road take note of how many times you have to slow down/ overtake and accelerate on the motorway when you are travelling at 70mph.
Travelling at 60mph:
Travelling at this speed you are doing all the extra manoeuvres I mentioned above at a significantly lower rate. You are travelling slower than most cars on the road but are going more quick than HGVs. So you don’t need to constantly slow down and accelerate for other cars. The only things you need to overtake are lorries and the insane who actually go slower than 60mph on the motorway.
You actually have the use of all three lanes, it’s actually hilarious to see how clear the left lane can be sometimes, you don’t have to slow down for anyone and you can see lorries and other vechiles with plenty time so you can plan for a overtake with plenty time and you won’t have to hit the breaks nearly so often.
I would implore you to try 60 mph and try 70 mph and you will see how difficult comparatively it is to stay at 70mph without slowing down or speeding up to overtake.
And is the reason for the savings that you will see in the calculations below.
I drive at 60mph and it makes the whole driving experience a whole lot more enjoyable, on my commute a lot of people do not believe me when I say this but I very rarely have to use my breaks or accelerate past this speed. I once did the M1 all the way to Birmingham without having to use my brakes a single time whilst I was on the motorway. (Aproximately 90 miles without using the brakes a single time)
Caveat is this mainly applies when the roads are a little more busy, if the roads are clear of course you will be able to keep an average speed.
I have owned two main cars for significant portions of time, the first was a Seat Leon FR 1.4L (SL) and the car I currently have is a Mazda 3 (M3) with a 2L engine. Another misconception that people have is that larger engines use more fuel, whilst generally true it’s essential to look at a cars MPG before you buy it when shopping. The Seat uses more fuel becuase the engine was less efficient and also has a turbo which increases its likelihood of using more fuel. Most reported MPGs for cars before like 2018 are incorrect and inflated values, but if you want realistic figures that people have recorded you can use this website (https://www.honestjohn.co.uk/real-mpg/).
Also some cars don’t have electronic MPG gauges and can sometimes be inaccurate so you can track them online, my reccomended one is Fuelly.
Anyways back to the article!
MPG savings (between two cars) Seat Leon FR 1.4L and Mazda 3 2L
My commute to work 12.5 miles, approx 25 miles there and back.
(Disclaimer this is according to car computer for the journey, but has been confirmed when looking at fuel costs and my mileage counter)
Travelling at 70 mph
SL: 37.8 mpg
M3: 42 mpg
Travelling at 60mph
SL: 45.8 mpg
M3: 52 mpg
What do these numbers actually mean in terms of cost. These are the theoretical fuel costs for travelling to and from my work place. Fuel cost = 145 pence per litre. (The link for the website calculator that I use is https://www.rac.co.uk/route-planner/mileage-calculator/)
Travelling at 70mph:
SL: £5.14
M3: £4.62
Travelling at 60mph:
SL: £4.24
M3: £3.74
Across both cars per day when you take a avergae that’s a saving of 89p per journey. However if you travel to work 20 times a month that’s now £17.80 in theory per month just on commuting.
Again this doesn’t sound that significant but considering a full tank of fuel costs +£60, it really is significant.
Range
Another important thing that should be mentioned is the range. The fuel tanks in both cars are 51 litres however the reserve volume was different for each of the cars. The Mazda had a reserve tank of 10 litres and the Seat had a reserve of around 5–6 litres. How did I know this?
If you google what the full tank capacity of your car is, and get your car to empty and refuel to a full tank you will never be able to put the full capacity in the car.
Fuel reserves are there for emergencies just incase you are stranded and are trying to get to a fuel station and things keep happening. It’s a good idea to have a rough idea what your fuel reserves are so that you can be more confident in situations where you will actually need it.
In the Mazda I refuel roughly 40 litres for a full tank, and in the Seat it was roughly 45 litres. So the range for each was as follows, in terms of commuting distance.
Driving at 70mph:
SL: 374.2 mile range
M3: 369.55 mile range
Driving at 60mph:
SL: 445.4 mile range
M3: 457.5 mile range
I have trust in the theoretical values because I used to take mental note of the miles I would reach before I had a fill up in each of the cars.
So not only do you use less fuel you also get more journeys out of a single tank. The highest range I ever got with the Seat Leon was a trip to Wales, I managed to around 550 miles with a single tank. That journey I reached around 55+mpg, and the reason is because the proportion of motorway driving to city driving was very very high, and the efficiency of your engine increases when the engine is properly heated, this is not the same as when you commute to work.
One interesting thing that I have not yet checked out yet is the maximum MPG I can achieve in the Mazda yet. In the seat I achieved 55 mpg for the whole trip and achieved around 560 miles with it, nearly 100 more miles than the commuting range. I have not yet done this with the Mazda but I am confident it will probably hit around 62+ mpg.
Revolutions per Minute
Familiarise yourself with the RPM gauge on your cluster for your car. Travelling up a hill at 60mph in comparison to a flat plane will increase the RPM that your car has to do to travel the same speed. Higher RPM means more fuel is being used.
From my personal experience cars usually are at ~2000RPM 60mph and ~2500 for 70mph on a flat road. When accelerating if you hit like 4000RPM you’re literally just wasting fuel, but I can’t deny its fun.
Environment
I won’t front and say I do this for the environment, because I will be real and say I don’t. But using less fuel and travelling further helps you do your bit for CO2 emissions. So if that’s more your forté then you can also do those calculations, however in the interest of my own time and sanity I will not. The RAC fuel calculator link above shows you what your estimated emissions will be but this varies from vehicle to vehicle.
Old Car Myth
I will just use a quote from a website but yes having a older car means that it can use more petrol, however this is if the car has not been maintained very well. But this doesn’t mean that you still won’t make savings if you drove slower, in fact it means that you will lose less money, as it will be even more inefficient at higher speeds.
“Some people believe that a car’s fuel economy deteriorates as it gets older, but this is a myth. A used car will still return new-car mpg figures — as long as it has been well maintained. If a car has a full-service history with lots of entries, it should deliver the same mpg as when it was new.
This is great news, as used cars are usually cheaper the older they get. This way, you can get an efficient car at a cost-effective price.”
Other Fuel Saving Tactics
As I said earlier, accelerating is one of the main uses of fuel in your car. If you are on a busy road, what do you actually gain by accelerating hard, just to break again shortly afterwards.
And that leads on to cruise control, if you have it use it for motorways. Again accelerating and decelerating is the biggest use of fuel in your car and if you let your car control the speed it is often more efficient. Just be careful with the use of cruise control on hilly areas, as then sometimes it can be less efficient, as people tend to slow down a little when going up hills whilst your car will try to keep you at that speed and increase the RPM which in turn uses more fuel.
AC, try not to have it on when you don’t need it. But you should turn your AC on even in winter every couple of weeks to make sure it still keeps working, turning on the AC every so often helps keeps all the parts of the system well lubricated.
Always fill to a full tank, I think this is overlooked one. A full tank means less extra journeys to the fuel station. Every time you go to a fuel station you have to use extra petrol to get there.
When driving on the motorway plan ahead and keep an eye out on cars further ahead, if they all start breaking you can see that it might be worth lifting off the gas pedal, instead of waiting and then using the breaks.
The End
I hope that you have learned something reading this page and would challenege you to try these for yourself and see if you notice and changes to your journey. Or even atleast incorporating more 60mph journeys into your routine will be beneficial. So for example travelling to work at 60 mph but 70mph on the way back. Because lets be real why the hell are you trying to get to work quickly.
Brice Adusei
