Regular Unleaded, Medium, or Premium?

What to choose? With three options at the pump, it is hard to know which to choose. A friend of mine asked me the other day, what is the difference between different octanes of gas? I had no idea. A girl I work with has an SUV and she is supposed to use premium gas; however, she said she has been using regular gas since day one and hasn't experienced any problems.

I went to Wikipedia, one of my favorite sources of random information, and found an answer. In the U.S., different octane grades range from 86-87 for regular, 89-90 for mid-grade and 90-94 for premium unleaded gas. The difference lies in the fact that high octane fuels "allow for a higher compression ratio - this means less space in a cylinder on its combustion stroke, hence a higher cylinder temperature which improves efficiency." High octane fuel also reduces the amount of hydrocarbons put out, which causes less pollution while getting better performance. Premium gas also has additional compounds put in it that allow for reduction of friction in the engine cylinders ; overall improving the engine and output. This kind of explains why a high-power, quick-maneuvering SUV may need a higher-octane fuel than a more basic, get-you- where-you-need-to-go-Honda, for example.

In a USAToday article titled "Why use premium gas when regular will do?" this issue is debated and it turns out that premium gas does not really make a huge difference in car performance. "Engines designed for regular fuel don't improve on premium and sometimes run worse. And today's engines designed for premium run fine on regular, too, their makers say, though power declines slightly." So, what are we supposed to do? I say use whatever you can afford and get regular tune-ups; and you should be good to go.