Need for Speed


What constant speed will provide the best mileage. We will assume you are going on a very long highway trip and want to know what speed will give you the best mileage. Here are some tips on fuel-efficient driving that will not only reduce greenhouse gas emissions and other pollutants, but could save you a lot of money per year in fuel costs.

Starting and hard braking can increase fuel consumption by as much as 40%. The proper way is to accelerate slowly and smoothly, then get into high gear as quickly as possible. In city driving, nearly 50% of the energy needed to power your car goes to acceleration.

Increasing your highway cruising speed from 90 km/hr to 120 km/hr can raise fuel consumption as much as 20%. You can improve your gas mileage 10% to 15% by driving at 88 km/hr rather than 104 km/hr.

Unfortunately, it is  true, your car's gas mileage decreases once it gets past its optimal speed. For most cars, this is around 90-96 km/hr. This means that every time you go over this speed, you are essentially wasting gas and money, and creating unnecessary greenhouse gases.

You would be surprised to know that a slight decrease in your highway driving speed can significantly reduce your gas consumption, adding only a few minutes to your travel time.

Avoid idling your vehicle, idling wastes fuel, gets you nowhere and produces unnecessary greenhouse gases. If you are going to stop for more than 30 seconds, except in traffic, turn off the engine. In winter, do not idle a cold engine for more than 30 seconds before driving away. Older vehicles, however, may need more idling time when first started. In cold winter conditions all vehicles may need more idling time to warm up and ensure the windshield is fully defogged. Be sure your vehicle is warmed enough to prevent stalling when you pull out.

Change gears and into top gear as soon as possible without accelerating harder than necessary. Driving in a gear lower than you need wastes fuel; so does letting the engine labor in top gear on hills and corners. Automatic transmissions will shift up more quickly and smoothly if you ease back slightly on the accelerator once the car gains momentum.

One of the most interesting facts was the old national speed limit of 90 km/hr which was created to address the energy crisis in the early 1970s, not safety purposes—although it did help safety.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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