So simple anyone can do it. If you’re caning it away from the traffic lights, you’re wasting petrol and your mpg will be down. If you’re endurance racing at 80mph on the motorway, you’re wasting petrol. Here’s the thing – your gas mileage can drop off as much as 15% between driving at or below 65mph and driving above 65mph. Now I love speed as much as the next person but you have to be realistic here – do you want better fuel economy or to get there marginally quicker? I sound like a total wet blanket telling you this of course, but driving slower absolutely will improve your mpg. Why? Because once you get over about 65mph, you’re using more engine power to overcome drag, which means consuming more petrol to do it.
What about when you’re not on the motorway? Well consider a little less braking if you can. If you can see the next set of lights ahead of you are red, don’t race up to them and come to a complete stop. Try to moderate your speed a little if you can do it safely. If you can get there as they turn green and the traffic in front begins to move, you’re doing OK. That’s because it takes more energy to get you going from a complete stop than it does from a slow roll. So if you can do this, it will improve your mpg.
It seems obvious but a lot of people just don’t know how to measure their average gas mileage. Fuel economy is a total mystery to them. So bear with me – I realise to a lot of you this is the age-old adage of teaching you to suck eggs.
So – a lot of cars nowadays have an mpg readout that you can select from their onboard computer. Whilst these are useful, they do tend to be a bit optimistic. I’ve found over the past 6 to 8 years that on-board mpg displays tend to over-read by about 7%. Not much but enough to give you a skewed view of reality. So how do you measure your average mpg? It’s easy. You need to start with a full tank and always fill your tank to the point where the pump cuts off. It’s painful to your wallet, especially at today’s prices, but it’s the best chance you have.
So first – fill up. Fill your car to the point where the pump cuts off and zero your trip counter. Now you know you’re starting from a ‘full’ tank. I say full because each car has a different amount of dead space at the top of the tank and in the fuel filler neck, but if you let the pump cut off on its own each time, it will generally fill to around the same level each time.
Next time you fill up, again fill the tank to the pump cutoff and importantly, make a note of the number of litres or gallons you put in, and the trip counter reading. Divide one by the other and you get either miles per gallon (mpg) or km per litre. Zero the trip counter again and keep a note of the mpg calculation.
Each time you fill up, fill it to the pump cutoff, and make a note of the amount that went in and the trip counter reading, calculating your mpg or litres per km each time.
Out of sight, out of mind. I’m guilty of this. Your air filter is what protects your engine from ingesting all the dust, dirt and crap in the air. If it’s doing its job well, it will clog up, much like the bag of a vacuum cleaner. Once it clogs up, your engine has a harder time sucking air through it. To compensate for the reduced airflow, the engine management system will richen up the mixture, using more petrol to keep the engine running smoothly. Replace your air filter once a year and you’ll guarantee better gas mileage. So why am I guilty of this? At the time of writing I change the three-year-old filter in my car and my mpg jumped by 2.5 overnight. On my car that equated to a 13% improvement for an outlay of $14. Duh! This is one of the easiest ones to do yourself too. Go out to your local parts store and look through their catalog to find the right filter (or use any of a myriad of online retailer who normally have better prices on aftermarket and performance stuff like K&N air filters). It will normally be a simple matter of some plastic or metal clips to get the airbox apart and then you can replace the old duffer with the new hotness.