Lesson 3: Accelerating
You’re probably familiar with Isaac Newton’s first law of motion: the law of inertia. Loosely summarized, it states that an object at rest will stay at rest until an outside force acts upon it and that an object in motion will remain in motion unless an outside force acts upon it. The second point is one we’ll deal with later. The first is one that probably impacts your fuel economy more than any single other thing.
An object at rest will stay at rest until an outside force acts upon it. Getting your car moving from a standstill is absolute murder on fuel economy because it puts your engine under tremendous load, which you might expect is when you consume the most fuel. It is.
Even under very tame acceleration, the sort that will get you honked at by anyone stuck behind you, your vehicle’s fuel economy can be 3 to 5 times worse than it is while cruising at a constant speed. Under typical acceleration, your fuel economy can jump to as much as 10 times worse and under hard acceleration even beyond that. If I told you that your typical family sedan was getting an instantaneous fuel economy of 25L/100km (7.8mpg) while accelerating, would you be surprised? You’re not driving a Hummer, after all. Get ready for the real surprise.
That would be a very respectable instantaneous fuel economy rating achieved by very modest acceleration. I’ve tested acceleration scenarios using a ScanGaugeII in my 2.3L Mazda3 and clocked fuel economy as low as 40L/100km (5.9mpg) under “spirited” acceleration. I’ve never bothered to test hard acceleration because the ecomiling rule for acceleration is already quite clear: don’t accelerate.
Seriously. We’ll talk more about this in future lessons but, since it’s not exactly practical to suggest that you never accelerate, the guideline for accelerating is that you should attempt to do as little as possible. Your ideal trip, from beginning to end, would have you accelerate once, cruise at a constant speed throughout and then decelerate and park. Once again, we’ll cover techniques for reducing the amount of accelerating you do by managing your driving style in future lessons.
And how do you accelerate when you are left with absolutely no choice but to do so? As slowly as you can or, more appropriately, as slowly as is safe. When your vehicle is stopped, the best way to go about minimizing the extreme amounts of fuel consumed under acceleration is to get your car up to speed nice and slow. You should not attempt to short shift (shift gears too soon) or start in second or produce any other scenario in which you lug the engine because this will, in fact, consume more fuel by unduly stressing the engine.
You can additionally save a lot of money when accelerating by considering the traffic and road conditions in front of you. Is there another red light a couple hundred meters down the road? Is road congestion so serious that traffic slows to a crawl shortly after the light? If so, why bother getting up to speed at all? Accelerate through the intersection at a safe but modest pace and then let go of the accelerator – coast into the obstruction ahead.
Takeaways from Lesson 3:
- Acceleration consumes tremendous amounts of fuel – remember this each time your foot touches the gas pedal.
- Accelerate from a standstill slowly and steadily – doing so will save you money.
- Do not short shift or lug the engine – unnecessarily loading your engine will cost you money.
- Keep your eyes on the road ahead – don’t accelerate into a situation where you will immediately need to stop or slow down again. You're in no rush to stop moving again.
It may seem counterintuitive that a lesson on accelerating encourages you to not accelerate at all, but that really is a key component of ecomiling. You want to keep your car moving forward at a consistent speed as much as possible so that you can avoid the very stressful and fuel-consuming act of accelerating. If you move on to Lesson 4, you'll learn how to do just that.
Lesson Quicklinks
Lesson 1: Get Started by Doing the ObviousDisclaimer: It is of critical importance that you always place safety first and fuel economy a very distant second. Although ecomiling may be an engaging, exciting and money-saving challenge, never place fuel economy above your safety or that of other road users. Obey all local traffic laws.