How to cut your car petrol costs in half

Jan16
by TFS on January 16, 2014 at 7:33 am
Posted In: Frugality, How To
How to cut petrol usage

Avoid these places if possible!

First all of I would like to say that we all know car use is for clowns. But let’s be realistic, I bet 99% of the readers of this site still use one, even if it is only very occasionally. Around 6 months ago our monthly petrol costs (or “gas” to my American friends reading) were coming in at around £150 a month (about 2 tanks worth) and I wanted to do something about it. The two key areas to tackle when you want to reduce petrol costs are:

  • Reducing usage of the car
  • Increasing MPG whilst using the car
There’s not much to be said about number one, you just cycle or in my case walk/run somewhere within a reasonable distance instead of using petrol power. The other alternative is just not to go somewhere, putting off and combining journeys. Do you really need to drive to the retail park just to buy a lightbulb, right now? Or can it wait until there are a few items you need, or can you source the item somewhere else? Simply by using this new perspective on car journeys our petrol costs dropped to about £110 a month. Not bad, but I knew we could do better!

Enter Hyper-Miling

The second point of increasing your MPG (Miles Per Gallon) is all about hyper-miling, a pretty cool sounding term that encompasses a whole range of techniques to make your petrol go further. Here are some of the most easy methods to implement:
  • Over inflate your tyres – I put mine up to 40PSI from the manufacturers recomendation of 36PSI
  • Drive calmly and sensibly – This sounds silly but there are so many irrate and unsensible drivers out there it has to be included as advice. Driving with calm acceleration and braking and not going too fast within any given speed limit will significantly increase your MPG, not to mention reduce the chance of you having a crash.
  • Rolling in neutral – When on a downhill or as soon as you see a car stopping or a red light in front you, simply knock the gearstick into neutral and coast it. This takes a bit of practice so don’t do it in heavy traffic at first, but after a few weeks it becomes second nature.
  • Cut the engine – when waiting at lights or when picking someone up. There is an urban myth that says starting up a car takes more petrol than letting it idle for 30 seconds, this is in fact not true, so you can ignore that and turn off the ignition now instead.
  • Get in the slip stream – Another tip to implement with caution. When on a motorway or highway if you can find a nice big lorry to get up fairly close behind your car will have to do less work pushing the air out of the way in front of it, as the huge vehicle up ahead is doing all the hard work for it. Just think of how teams of cyclists work together in the Olympics or the Tour de France, it’s the same principle! This will save you petrol and increase MPG, or your legs’ energy if you happen to be riding up L’Étape!
  • Ditch the excess baggage – Any extra items in your boot should be removed when not strictly necessary for the journey. I used to forgetfully leave my golf clubs in there sometimes for example, not anymore! You can also take out the spare wheel if you want as they are pretty heavy, but make sure you have some other sort of back up if you get a puncture (those expanding / hardening foam kits you can get should do the trick). It goes without saying that roof racks and what not should be removed as well.
  • Fill up your tank in the morning – Petrol is more dense when it is cold, so if you fill up before the air temperature rises then you should in theory receive more petrol bang for your buck. (I’m quite dubious about this one and sure the petrol pumps take temperature into account, but it’s worth a go I suppose)

The results of Hyper-Miling

I did an experiment to test our mileage on a full tank before and after putting some of the above into practice, the results were as follows:
Before: 394 miles = 29.87 MPG (assuming the full tank was used, so probably slightly over. This is bang on the quoted figures from the manufacturer)
After Tank 1: 410 miles = 31.08 (assuming full tank used)
After Tank 2 (I only used 52.5 litres before I filled up this time, I could tell because that is how much it took to fill up the next time): 405 miles = 35 MPG
Average After figure: 33.07 MPG
This is roughly another 10% increase in mileage, not a show stopper but enough to get our petrol bill down to near £100 a month. Also my method was somewhat unscientific and I could have done with repeating the before and after figures over a few more tanks to get better figures, but you can see there is a clear increase there right off the bat. I am pretty convinced that the whole 10% is just from keeping the tyres inflated to a decent level, so if you enact one piece of advice then make sure it is that one. I rarely drive the car you see and Mrs TFS was not comforable trying the rolling in neutral trick, so the juries out on that one. She has always driven sensibly anyway so no difference in the before and after figures there either, and again there was no excess baggage with either tank. So the takeaway is clearly, check your tyre pressure regularly!
You can read more about hyper-miling here and about many matters on efficiency on Bakari’s excellent blog here. He also has lots of whacky but cool ideas about modifications to engines and the aerodynamics to cars which are  summed up on this instructables page

Meet the new TFS-Mobile!

All of these tips above are great for increasing MPG whatever car you have, but after of all that, it then occured to me that the car you are driving actually is the key factor. This is why one of my tasks on my “to do” list was to get a new car, with better MPG. So without further ado please meet the brand spanking-used TFS-Mobile:

Saving money on Petrol

Saving wads of cash on petrol with a more efficient motor!

The logic behind this was simple: We had a car who’s base rate MPG was around 30 MPG, a Peugeot 306 with a normal 1.8 litre unleaded petrol engine (we should sell this for £500-ish). I liked the old TFS-Mobile a lot (RIP) so had a quick search for what model in the same/similar range had the highest MPG, and it turned out to be the 307 2.0 litre HDI, a diesel engine, weighing in at 55 MPG (We bought one for £1300). With our extra 10% from the hyper-miling techniques we should be able to get that up to 60 MPG, therefore cutting our petrol bill in half compared to a few months ago, and actually destroying it down to 33% compared to 6 months ago, before we stared any of this malarkey. This will net us a sweet petrol cost savings of £1200 per year. That’s pretty impressive, and even though the cost of buying the car and selling the old one is not insignificant, we’ll make the money back within 8-10 months of driving the new car.

Now it’s common knowledge that diesel engines have greater efficiency, I’m not exactly giving you some sort of secret society insider tip here, but how many of you out there are actually driving a diesel right now? How many of even know exactly what MPG you are getting in your current car, or take it into consideration when you buy a new one? I’d be interested to know if people can drop me a comment below! What engine have you got? How much mileage do you do and what MPG are you getting? Has anyone upgraded to any of the newer mega-efficient cars out there? Most importantly have you got any other tips I have missed out, as I’m always looking to squeeze a few extra percentage points out of my MPG stats!?

Thanks for reading and I hope you found the tips useful!

TFS