Out of Gas

Photo credit: Benjamin Stein
Highway 7

~ Joseph Meier

Silver, gold, platinum; these high grade fuels cost more and make big promises. Unfortunately, the so-called premium gasolines may not deliver in all car models. With Secretary of Energy, Chew supporting high gas prices, President Obama reducing federal drilling leases, and continuing instability in the Middle East, energy pricing is extremely volatile. Thrift has become a necessity. Knowing more about the car you drive and modern mechanics might help ease the financial pressure at the pump. Understanding the grades of gas, compression ratios, and how the two work together in your engine may literally help everyone get more bang for their buck.

Consumers might be surprised to know that the higher grades of gas are actually more difficult to ignite. During the refining process, each individual barrel of crude oil will produce a myriad of different products: gasoline, diesel, jet fuel, and an assortment of plastics. Each of these products require varying degrees of heat and pressure to ignite. These products are as diverse as their applications. When it comes to saving money at the pump, application is everything.

Compression ratio and forced-air induction are crucial in the practical application of different fuel grades. As previously stated, the expensive gas does not combust easily. It is for this reason that 93 Octane is the preferred fuel for high performance vehicles. The compression ratio measures how much air is displaced as the piston rises to its Top Dead Center (TDC). At this point, the spark plug will ignite the air-fuel mixture. Most all performance car websites discuss compression ratios and how they relate to power. According to the well-known car enthusiast website Popularhotroding.com, “At least 150hp of a Pro Stock engine is due to ultra-high compression ratios.” More pressure equals more power.

The same affect can be achieved by forcing air into the cylinder from outside of the engine. Forced-air induction systems are more commonly known as turbo and super chargers. They both achieve the same goal but by different means. The less combustible fuels must be used in high compression engines. In high compression engines, the lower grade fuels will combust before the piston reaches its TDC. This will cause an odd sound known as engine ping. The inconvenient truth, for those in the hydrocarbon industry, is that most cars do not require premium gas and will not benefit from it.

John Miller, a twenty-year employee of Penske, has spent a fair part of his life immersed in the world of auto mechanics. When asked if putting premium gas in a typical economy class vehicle was a waste of money, he responded, “Absolutely, absolutely.” Mr. Miller spoke about octane levels and how they related to compression ratios saying, “Compression ratios dictate what octane rating you should use.” In his opinion, a compression ratio of 9.5 to 1 is the premium gas threshold; anything under will not deliver the result for the extravagant cost. Do you know the compression ratio of your car?

The owner’s manual will, in most cases, identify the compression ratio and whether or not the car has a forced-air induction system. The internet is also a good resource. According to Mr. Miller, the owner’s manual may suggest a higher grade of gas than your vehicle actually needs. Apparently, he followed the manufacturer’s prescribed fuel choice, until he learned more about his powertrain. Miller’s research combined with his own knowledge of fuel and mechanics led him to save money. Are you throwing money away on the expensive gas?

Silver, gold, platinum, these words imply quality and promise performance, but deliver question and conjecture. Bottom line, sometimes knowledge means money.