Most drivers dread filling up at the pump. With gas prices as high as they are right now, saving money but sustaining vehicle performance with the fuel we choose are about the only things that matter. We need to get the most out of our vehicles for the longest possible time, which usually means maintaining it rather than spending thousands on costly repairs or a new vehicle. In order to get the most out of their vehicle, some people tend to spend more on their gas, choosing a higher octane fuel rating because they assume that their car will perform better and they will have better gas mileage. By understanding what fuel octane is and how it affects your engine, you can see that this is not necessarily the case and you can instantly save money at the pump by using the gas that your car requires and nothing more. In a consumer notice, the Federal Trade Commission says that “in most cases, using a higher-octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your car perform better, go faster, get better mileage or run cleaner.”
Octane ratings measure a gasoline’s ability to resist engine knock. The numbers relate to the fuel’s octane rating. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane), and premium (usually 92 or 93). The ratings are posted on bright yellow stickers on each gas pump near the corresponding nozzle. The higher the number, the slower the fuel burns. An internal combustion engine uses pistons to squeeze fuel until it explodes. With high octane fuel, the pistons need to put more pressure on the fuel to get it to ignite. With the exception of a few high performance luxury vehicles and specially-designed engines, the majority of vehicles on the market are designed to use regular octane. High-compression engines in sport or luxury automobiles need mid-grade or premium gas to prevent knocking. The best way to know what is recommended for the vehicle you drive is to read your owner’s manual and to pay attention to the ratting noise also known as “engine knock.”
So what exactly is engine knock? According to auto experts, it is defined as a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. This means that the fuel is igniting too soon and may create too much pressure that the engine simply cannot sustain. When vehicles that are designed to use premium gasoline are filled with regular gasoline, problems like the latter can occur. When your vehicle is designed for premium gasoline, this is the circumstance that you do not want to put a lower grade fuel in the vehicle. The ignition timing will be off and the “engine knock” will commence. On the other hand, most people believe that buying a higher-octane rated fuel will benefit their engine and that is just not the case. Choosing a higher octane rating will not affect performance or gas mileage as many drivers believe.
Contrary to popular belief, high octane gasoline doesn’t outperform regular octane gasoline in preventing engine deposits of dirt and residue from forming, removing them, or cleaning your vehicle’s engine. The U.S. Environmental Protection Agency (EPA) requires all gasoline – every single brand – to contain engine cleaning additives to protect against the build-up of engine deposits. These deposits can cause serious issues and reduce performance. This build-up in the engine has been compared to a slow and deadly engine cancer, reducing power, fuel efficiency, and even drivability when left unaddressed for too long. Although modern technology is producing cleaner-burning, more efficient engines and vehicles, engine deposits are still a major problem for consumers. These deposits are a byproduct of combustion of fuel, and the areas that are most susceptible tend to be the combustion chamber and fuel-intake system, which includes the intake runners and ports, carburetor or fuel injectors, and the intake valves.
In both carburetors and fuel injectors, fuel is filtered through small openings. Over a period of time, fuel evaporation can gradually cause a buildup in these openings, and if left unchecked, can block the holes. This restricts fuel flow and reduces engine performance. “The opening of a port fuel injector is about the width of a human hair,” states Tom Mulrane, manager of research and development for STP Products. “So it takes very little deposits to clog them up. Automakers generally agree that as little as 10% flow restriction in a single fuel injector can result in hesitation, stumbling, stalling, and loss of power.” Combustion-chamber deposits may raise the octane requirement of the engine, increasing the likelihood of knocking or pinging even though the higher octane fuel is not really recommended. Keeping an engine clean is just as important as the gas you choose.
If you do hear the knocking or pinging noises, it is suggested that you try alternating to mid-grade or premium gasoline the next time you fill up at the gas pump. If the noises continue after a couple of fill-ups, it likely means that you need a service or tune-up. Once that work has been completed, we suggest that you try to go back to regular octane or as your owner’s manual recommends. But why is mid-grade and premium gasoline more money? Premium gas costs 15 to 30 cents per gallon more than regular gas. That can actually add up to at least $100 or more a year in extra costs which were not necessary in the first place. Studies predict that drivers may currently be spending hundreds of millions of dollars each year for higher octane gas than they need. The typical vehicle in 2009 averaged between 20 and 25 miles per gallon. Spending extra money on higher grade gas to increase fuel mileage when it really doesn’t impact fuel efficiency at all is frustrating news for many consumers who think they are treating their vehicle to something special. In this country, statistics show that drivers spend around $3600-$4000 per year on gas at the pump. That’s roughly $1 out of every $12 of median household income-the highest amount in about three decades!
As you drop some serious cash at the pump, just remember to know the facts about fuel octane ratings. If your owner’s manual recommends regular octane gas (87), do not feel like you will be doing your vehicle a favor by choosing a higher grade. It will not impact performance, ability, or fuel mileage. Your money is much better spent on ensuring that routine auto maintenance and services are completed and that your engine is clear of harmful deposits. Know your octane and know your gas.