Fuel Mileage Series : Introduction to Fuel Economy

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Background: Fuel Economy

Contrary to popular belief, fuel efficiency of the internal combustion engine hasn’t increased tremendously since the the introduction of Fuel Injection (fuel injection is the process of electronically pulsing a measured quantity of pressurized fuel into an engine) in the 1980s. For instance the 1986 Chevrolet Sprint achieved an astonishing average of 48MPG or 4.9L/100km, which is almost identical to the 2014 Toyota Prius, or my 2000 Honda Shadow Motorcycle! My first car, a 1993 Honda Civic hatchback was achieving an average of 5.7/100km or 40MPG, which is still impressive today.

 

WHY?

Naturally everyone wants to use less fuel, and travel further. It is more cost effective and better for the environment. Combustion engines use a mixture of air (oxygen) and fuel (gasoline or diesel) to create mechanical energy. The ideal ratio of the air and fuel mixture is 14.7 : 1, or 14.7ml of air to every 1ml of fuel. If you use less fuel, the mixture can burn hotter and detonate early (sometimes causing engine damage). If there is too much fuel, the result is incomplete combustion, poor emissions, and wasted fuel.

Since there isn’t much room to modify the air fuel ratio, the only other option is to reduce the amount of air and fuel an engine consumes. This consumption is directly related to an engines size or displacement (displacement is the volume of air and fuel an engine uses in a single cycle) . For example, a 1.5L Honda 4 cylinder engine will consume less fuel than a 3.0L BMW 6 cylinder engine when idling at the same speed under identical load conditions. When determining a vehicles overall fuel efficiency, there are many  factors to consider beyond the scope of this writing, but fuel efficiency is largely based on engine size.

 

Moral of the story?

If you want a more fuel efficient vehicle, buy a vehicle with a smaller engine. Historically smaller engines have produced less power, but automakers are placing a strong focus on lower displacement engines with high power outputs. Mercedes-Benz AMG (in 2016) produced a record breaking 2.0L 4 cylinder engine that produces a whopping 375 Horsepower. This engine, and many other powerful engines utilize turbocharging technology which is essentially forcing compressed air into the engine. As with a naturally aspirated engine (no turbo) the air/fuel ratio remains the same at 14.7… So more air, more fuel!

If fuel economy is a factor when looking for your next vehicle, don’t discount the used market! There are many incredibly efficient vehicles for under $10,000!

 

 

Other notes…

One of the most fuel efficient vehicles of all time was the 2000 Honda Insight, achieving  53mpg or 4.43L/100km.

Aside from the pricey Chevrolet Volt and BMW i3, the Toyota Prius and Honda Civic/Insight have been leading the market since the early 2000’s

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