Introduction – Aggressive Management Will Improve Gas Mileage
One of the great ways to reduce energy use and carbon intensity of our activities is aggressively taking advantage of every little opportunity while driving very carefully. This will improve your gas mileage. Drivers who are the most aggressive in taking such opportunities are called “hyper-milers”.
Getting better fuel economy is just one way to cut driving emissions. In time we will also cover driving less, sharing more trips and choosing a lower carbon vehicle, but getting better gas mileage from your current car is a good place to start.
So what are the methods to improve gas mileage? Let’s start.
Let’s Define Efficiency Before We Optimize For It
First lets settle on what we mean by efficiency. It’s actually a measurable value. Here we mean how far a vehicle can be driven, for a given amount of gas or petrol. The efficiency isn’t even a “fixed” thing. For example how far you can drive it might depend on the speed. If you drive over 50 mph, then the engine is inefficient. And over the same distance, it uses more fuel than if you had driven it at lower speeds. In the US, we use “miles per gallon” to measure fuel efficiency for a car. Miles per gallon is abbreviated to MPG.
1: Measure Or Monitor Your Fuel Economy To Improve Gas Mileage
Measure, measure, measure. One of the most important things to do, before you start improving or optimizing, is to know what you’re improving or optimizing. You even want to know where you’re starting from. It may be boring, but it matters in two ways.
Firstly, you have many patterns of travel. You drive to work, drive for leisure, drive to supermarket, drop off kids etc. Averaging over the whole picture means good measurements. Measuring fuel economy will establish a baseline for you to see if making changes to your driving has a considerable effect on your fuel gas mileage.
Secondly, using your measuring device you get instantaneous measurements. This data lets you optimize your driving style for fuel gas mileage. This is particularly useful for improving the way you accelerate and finding the speed at which your car is most economical.
2: Always Maintain Your Car Engine
Looking after your car can not only help you improve gas mileage, but is important for safety and the longevity of your vehicle.
According to the EPA having your car properly tuned improves its gas mileage by up to 4%. The reasons are mundane. For example, properly inflating tires can help as much as 3% and using the correct oil is good for up to 2%.
Essentially you want to make sure your car is rolling smoothly and combusting fuel efficiently. Bad wheel alignment, an under-inflated tire, dirty filters or a dodgy spark plug can let your vehicle down but are easy to fix.
Do you have a modern car? Then the key advice is to have the vehicle inspected by a mechanic when the check engine light comes on.
3: Reduce weight of the car
Having unnecessary weight in your vehicle wastes fuel, particularly during acceleration. If there is heavy stuff in your boot you don’t need, ditch it. Losing 100 pounds (45 kg) will improve gas mileage by around 2%. In fact the push to make cars lighter is playing a leading role in improving fuel economy in new cars. Less weight on car makes them lighter and more prone to damage without optimization engineering of safety.
4: Reduce drag on your car
Once you get to about 30 mph (48 km/h) a car uses more energy to overcome wind resistance than it does fighting rolling resistance. So you want your car to be as aerodynamic as possible for highway driving.
Having your sun roof open or windows down can increase drag a little at higher speeds. Leaving a roof box or bike rack on will have a larger effect, but estimates vary widely on this from a 1% to a 15% reduction in fuel economy.
5: Smoothly accelerate and decelerate and reduce braking
Accelerating quickly on your push bike is a strain on your legs, and it’s no different for your motor. But accelerating too slowly can also limit fuel economy if it keeps you in lower gears for too long, where fuel economy is poor. Let’s break that down into 3 phases.
Accelerate phase – as a rough idea you want to take 15-20 seconds to get to 50 mph (80 km/h). This would combine a relatively gentle start in the low gears with a more rapid shift through the middle gears before settling at an economic speed (40-50 mph) in top gears.
Constant speed phase – once your reach an efficient speed, maintaining a constant pace avoids wasting energy on decelerating and then accelerating again. Cruise control can help with this, but some people also find pulse and glide techniques effective.
Braking phase – when it comes to braking, less is more. Braking takes useful kinetic energy and turns it into waste heat. Anticipating road conditions and coasting in gear to a stop makes the most of your car’s momentum, as long as it is done safely.
The relevant situation for which this advice doesn’t hold is for e-vehicles with regenerative braking which convert the energy of braking back into energy for the car. There’s no need to spare braking in this case.
If done well smooth driving can also be safer, more relaxed and better for your car.
6: Reduce rev’ing your engine
Over revving your car is an easy way to waste fuel. As a general rule you want to change up a gear before reaching 2,500 revs. In a diesel car this figure is closer to 2,000 revs. Although the optimum revs for fuel economy can be even lower in certain cars.
It is often quite surprising just how early you should be changing up to maximize gas mileage. Your car’s manual sometimes gives guidance for this.
7: Keep your top speed in the range of 40-55 mph for maximal gas mileage
Driving slower will save you gas. Drive no faster than 50 mph to increase your gas mileage. Gas mileage normally peaks at a speed of 40-55 mph (64-89 km/h) while using your cars top gear. It can vary significantly between cars based on the gearing, engine, weight and drag, but after 60 mph it generally declines quite significantly.
Recent research by the Oak Ridge National Laboratory comparing the fuel economy of 74 vehicles at speeds of 50, 60, 70 and 80 mph shows each additional 10 mph beyond 50 mph reduces fuel economy by about 14%. In fact, we had shown this data on fuel economy as a function of speed. Fuel economy is fairly constant at low speeds, and drops off after 55 mph.
More simply put, from 50 to 60 mph fuel economy drops by 12%, from 50 to 70 mph it drops by 25%, and from 50 to 80 mph it falls by 36%. But it’s ok to drive slowly. There doesn’t seem to be a big fuel economy hit from driving too slowly.
If you are a bit of a lead foot on the highway, slowing down will improve your fuel economy considerably. Obviously you can only go as slow as is safe, but cutting just 10 mph can pay large dividends and will probably make your driving smoother too.
8: Use gravity – slower up a hill and coast down
Working with gravity, rather than against it, is something hyper-milers advocate on hills. Letting your car go slightly slower up a hill, then coasting down the other side in gear will maximize economy by trading some kinetic energy for the stored energy of being higher. This tactic should only be employed when it is safe to do so.
9: Reduce engine idling – use the stop-start feature or turn it off
Modern cars don’t really need much time to warm up, it just wastes fuel. If you are waiting for someone, or stationary in traffic, for more than 30 seconds you are better turning the engine off, assuming it is safe to do so.
10: Turn down the car air conditioner
Although electric gadgets do use energy in your car, it tends to be a negligible load for the motor. The only thing really worth considering for fuel economy is air conditioning, which at low speeds can reduce fuel economy by more than 10% on a high setting.
11: Avoid traffic to reduce inefficiencies of driving
This last tip is a little silly, as no-one in their right mind goes looking for traffic. But all the same nothing will ruin your fuel economy like the stop-start of getting stuck in traffic.
Although it is much easier said than done, planning ahead can occasionally help you avoid traffic. A quick check of your radio or smart phone might alert you to an accident or traffic jam.
In fact, Google Maps in Oct 2021 released an “eco routes” option. The option shows the map user alternative “eco routes” that use less fuel than the main route accounting for distance and speed. This is on top of their biker routes and scooter share information. All three features fit into the “sustainable” Google effort.
In the US, city drivers also employ the tactic of making more right turns even if it adds some distance, because it can help reduce time idling in traffic.
12: Use the correct engine oil to boost efficiency
The EPA also suggests using the correct engine oil. Two ways to identify the correct engine oil are as follows: One of those things is to use the manufacturer’s recommended grade of motor oil. Another thing is to look for motor oil that says “Energy Conserving” on the API performance symbol to be sure it contains friction-reducing additives. Here is the symbol:
Bringing it together to improve gas mileage
Adding up all the improvements listed in this post it is tempting to think you can get double the gas mileage from your car with some simple changes. Obviously this just isn’t this case. Each car has physical limitations that even a hypermiler can’t overcome.
But improving your fuel economy by 15-25% is entirely plausible. If you currently drive quite aggressively, or at high speeds, even greater gains might be possible.
That would be good news for both your carbon footprint and your wallet.
I founded Shrink That Footprint in November 2012, after a long period of research. For many years I have calculated, studied and worked with carbon footprints, and Shrink That Footprint is that interest come to life.
I have an Economics degree from UCL, have previously worked as an energy efficiency analyst at BNEF and continue to work as a strategy consultant at Maneas. I have consulted to numerous clients in energy and finance, as well as the World Economic Forum.
When I’m not crunching carbon footprints you’ll often find me helping my two year old son tend to the tomatoes, salad and peppers growing in our upcycled greenhouse.