"Put a tiger in your tank," says a classic advertising tagline. In today's motoring world, what kind of fuel grade will have the power to place a beast in your gas tank?
The answer, according to experts who study fuel efficiency in detail, is both regular and premium gasoline. And it would be a waste of money to favor premium over regular, especially in these times when gasoline prices are high, according to the experts.
Virtually nothing is gained by filling up with a premium or more expensive grade of fuel than the vehicle manufacturer has recommended, the experts say. And many of the same experts explain that drivers may not lose much performance from their cars by using a lower grade of fuel than recommended by the car manufacturer.
There is little difference in energy content of regular versus premium gasoline. They both contain about 111,400 British Thermal Units of energy per gallon.
The price difference, however, between the fuel grades is anywhere from 20 cents to 40 cents, depending on where you live in the United States. The experts' consensus goes against the long-held belief by thousand of drivers who fill up with premium only, or on every third or fourth trip to the pump. The idea is to fill up with premium every so often to clean out the engines or rev up the performance of older engines.
But according to the experts, this practice is like tossing quarters in a wishing well, since most engines are designed to operate on relatively low-octane regular unleaded gasoline.
Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.
The American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command.