Myths about fuel economy

Remember when you were a kid and your parents used to take you shopping for school clothes? There was probably a new pair of sneakers on the list. The best way to find out if shoes are good is to run around the store and see if they make you go faster.

Of course, the shoes that made you run the fastest were the ones you wanted. However, it is a myth that some running shoes will make you faster than others.

The same is true for cars. We were brought up on crazy myths. Many of these have been passed down from previous generations and are of dubious accuracy. Others are distributed in casual conversation, but are accepted as facts.

Below are some myths about fuel economy that may burst your bubble:

Topping your car

At one point or another, we've all stood at the gas station when the injector turned off. You grab a pen to try and squeeze every last drop into your tank. Filling the tank to the maximum capacity is good, right? Nope.

The fuel pump nozzle is designed to stop when the tank is full. By trying to pump more gas into your car after it's full, you're actually pushing the gas back into the evaporative system - basically the evaporative canister - which can destroy it and the evaporative system. Refueling is the main cause of canister failure and can be costly to repair.

Clean air filters

Most people think that a dirty air filter reduces fuel consumption. However, the reality is that this is not true. According to FuelEconomy.gov, a dirty air filter has minimal impact on gas mileage in late-model cars. A well maintained fuel injected engine will still deliver the expected fuel economy no matter how dirty the air filter is.

Late model vehicles with fuel-injected engines have on-board computers that calculate the amount of air entering the engine and adjust fuel consumption accordingly. Air filter cleanliness is not part of the equation. This does not mean that you should not replace your dirty filter with a new one. It's a good habit to change the air filter as it gets dirty.

An exception to this rule are older cars produced before 1980. In these vehicles, a dirty air filter adversely affected performance and fuel consumption.

Cruisin'

It is logical to think that maintaining a constant speed will save fuel, and there is no better way to maintain a constant speed than cruise control. If you're driving on a flat stretch of highway, that's true, but highways are rarely flat. When your cruise control detects an incline, it accelerates to maintain the desired speed. The acceleration rate may be faster than the rate at which you would accelerate on your own.

Rapid acceleration kills mileage, so take control of your car when you see bumps in the road, accelerate gradually, and then turn cruise control back on when the road flattens out.

The sensors tell you when to check your tires.

When was the last time you checked your tire pressure? Maybe the last time the low pressure sensor worked? Maybe you can't even remember. According to the National Highway Traffic Safety Administration, a third of all car tires are not inflated. If the tire pressure is too low, the tires can overheat, cause excessive friction on the road, wear prematurely, and worse, blow out. Check tire pressure once a month. The recommended tire pressure is either inside the fuel filler flap or in the glove compartment. It is important to remember that you need to check the pressure in five tires, not four: do not forget the spare tire.

Don't drag behind

Anyone who has watched the Tour de France knows that pedaling behind the other rider reduces wind resistance. It goes without saying that if you are behind a truck (or a car that is larger than yours), it will protect you from the wind, thereby reducing fuel consumption. Based on pure physics, this theory is correct. However, following a truck to increase gas mileage is a really bad idea. The extra efficiency you can get is not worth the risk of an accident.

Premium gasoline will help increase mileage

Your vehicle is configured to run on gasoline with a specific octane rating. If you're running a premium in an engine that's designed for general use, you could be throwing money away. If you're unsure, Edmunds suggests doing your own test. Fully fill the tank twice with regular gasoline. Then fully double fill your car with premium. Record your mileage and gallons used. Pay attention to fuel consumption and performance. If regular gasoline is recommended for your car and you fill it with premium gasoline, chances are you won't notice much improvement.

However, if your car is rated premium and you fill it up with a regular one, you may see a performance drop of 6 to 10 percent according to the Car and Driver test.

Get small or stay at home

Common sense dictates that small cars like the Mini Cooper will rock the world when it comes to mpg. Edmunds tested the car in both city and road conditions, and the five-seat Mini (who knew it could seat five?) earned 29 mpg in the city and 40 mpg on the open road. Respectable numbers, to be sure.

But not all economical cars have to be miniature. The Toyota Prius V, the larger 5-seat hybrid wagon, gets even better at 44 mpg city and 40 mpg highway.

As the Mini and Prius V show, it's not the size of the car that matters, but what's under the hood. Previously, only small cars were supplied with economical hybrid engines. More and more standard-size cars, SUVs and high-performance sports cars are using technology with hybrid powertrains, diesel engines, turbochargers and low rolling resistance tires. These advances allow many new mid-sized and large vehicles to save fuel better than ever before.

Manual transmissions increase mileage

Edmunds' 2013 report dispelled another mileage myth. For many years, manual transmission cars were thought to have higher mileage than their automatic counterparts. “Not true,” says Edmunds.

The number of manual transmission cars sold each year ranges from 3.9% (Edmunds) to 10% (Fox News). Regardless of which automatic transmission you choose for the direct test, manual and automatic vehicles will perform about the same.

Edmunds compared the Chevy Cruze Eco and Ford Focus versions with manual and automatic transmissions. The Chevy's manual transmission averaged 33 mpg in combined (city-highway average) and 31 for the automatic. The six-speed Focus gets 30 mpg compared to the automatic version at 31 mpg.

The improvement in gas mileage for automatic transmission vehicles is due to advances in technology and an increase in the number of additional transmission gears - some new automatic transmissions have as many as 10 gears!

The fuel efficiency gap between automatic and manual vehicles is now virtually non-existent.

High performance means poor mileage

Baby boomers were raised to believe that if you want to drive a high performance sports car, you have to live with lousy gas mileage. In their experience, this was true. The classic 1965 Ford Mustang Fastback, for example, got about 14 mpg.

Remember the Firebird from the Rockford files? It got 10 to 14 mpg. Both machines had performance but at a price.

Tesla has dispelled the myth that super powerful cars can be economical. The company is building an all-electric vehicle that can sprint to 60 km/h in less than four seconds and travel 265 km on a single charge. Tesla's downside is its price.

Fortunately for consumers, there is now a sweet spot. Most major car manufacturers offer cars that look sporty, offer superior performance, have plenty of luggage space, and get close to 30 miles per gallon of combined gasoline, all at modest prices.

Cars are always economical

The car's engine is running at peak efficiency after only a few thousand miles. Over time, the efficiency of the car due to increased friction, internal engine wear, seals, aging of components, bearing wear, etc. takes its toll and the engine also stops working. You can do your best to keep your car in top condition by tuning it regularly, but it will never be as good as new again. As a general rule, when you buy a new car, miles per gallon will stay constant for a while and then slowly start to decline. This is normal and expected.

What's in the future?

In 2012, the Obama administration announced new standards for fuel efficiency. The administration has called for cars and light trucks to reach the equivalent of 54.5 mpg by 2025. Improved gas efficiency is expected to save motorists more than $1.7 trillion in fuel prices, while oil consumption will be reduced by 12 billion barrels per year.

Thirteen major car manufacturers and the Amalgamated Auto Workers have pledged to work together to create more efficient vehicles that reduce greenhouse gas emissions.

Over the next decade, electric vehicles, hybrids and clean cars will become the norm, and we can all drive cars that go 50 mpg (or hundreds of miles on a single charge). Who wouldn't like to use less fuel?