10 Things You Should Know About Gasoline
Do you think premium gas is free of ethanol and the best choice for small engines? Do you ever treat your car to an occasional tank of premium because you think it cleans fuel injectors better and provides more power? If you’ve ever been confused by which gas to use and why, this story is for you. We consulted gasoline expert Fred Walas of Marathon Petroleum Company, the fourth-largest refining company in the United States. He gave us the lowdown on regular vs. premium fuels, and answered all our burning questions about gasoline.
Is Premium or Mid-Grade Fuel Worth the Extra Money?
Premium gas doesn’t provide any more power or contain better additives than regular gas, and it contains the same amount of ethanol as other grades. It just resists detonation (knock) better than lower-octane gas—nothing more, nothing less.
Some brands place slightly more detergent additive in their premium than in their other grades, but all grades meet the minimum required by the EPA. Bottom line? The carmaker knows best, so use the octane-rated fuel that’s called for in your owner’s manual. If your engine requires or ‘recommends’ 89- or 93-octane fuel, that’s what you should use to get peak performance and fuel efficiency. But there is an exception to the rule.
If you have an older car that’s designed for 87-octane gas and it knocks when you punch the pedal, try filling it with 89-octane fuel to see if the knock goes away. If so, keep using 89-octane to regain some power and save your engine.
How Long Can Gas be Stored?
If you store gas for your small engines in a tightly sealed container (allow some room for expansion at the top of the can), it’ll last for a season. However, if your gas container doesn’t seal tightly or you leave the spout off, airborne moisture and condensation can cause ethanol separation, oxidation and gum formation. Ethanol corrodes the carburetor and damages fuel line components, and gum, well, just gums up the works.
Adding fuel stabilizer to fresh gas reduces the risk of separation, oxidation and gum formation, but it can’t compensate for sloppy handling. Investing in a better-sealing gas container costs a lot less than a carburetor rebuild.
Are There Any Gas Additives Worth Using?
No ‘magic’ or ‘revolutionary’ additives will increase your fuel efficiency. However, some owners like to add fuel-system cleaning additives periodically. Many companies make the type you add to your tank. The most effective ones have polyisobutylamine (PIBA) and polyetheramine (PEA), so look for one of those ingredients on the label. Follow the product’s directions for treat rates. Avoid all other gas additives!
Is a Major-Brand Gas Better Than a Lesser-Known Brand?
Twenty years ago, there was a difference between gas from the major brands and ‘cheap’ gas from no-name stations. Today, the biggest difference between gasoline brands is the type of fuel-system cleaning additives used. However, the EPA mandates a minimum level of fuel-system cleaning additives, and all gasoline sold in the United States must meet those levels.
There are other, minor, differences. Gasoline is a blend of more than 150 components, and every brand uses its own formula. So you may find that one brand performs better than a different brand in your car or provides a slight mileage advantage. However, that same brand and grade may not perform as well in a different engine. So it’s impossible to make broad claims that one particular brand is best for all vehicles.
What’s the Best Way to Dispose of Old Fuel?
You can add up to 1 gallon of old gas to your vehicle’s tank, but it should be nearly full of fuel to dilute the old gas. However, you should take old premixed (oil and gas) fuel for two-cycle engines to a nearby hazardous waste recycling center. Don’t add it to your car or truck.
What is Non-Oxygenated Gas?
Refiners add ethanol to gasoline to increase the fuel’s oxygen content and to comply with federal law. As a side benefit, ethanol is one of a few gasoline components with a high octane rating. Nonoxygenated gas doesn’t contain ethanol, so it eliminates corrosion problems when left in the fuel system for long periods. That makes it a great choice for engines that are stored in the off-season. Plus, it’s the fuel to use if you own an older boat that wasn’t designed for ethanol fuels.
But non-oxygenated gas isn’t entirely trouble free. It still oxidizes and forms gum over time, so you should observe the same fuel storage precautions and treat it with fuel stabilizer when you buy it. To find a station that sells ‘nonoxy’ gas, go to pure-gas.org.
What’s the Difference Between Summer and Winter Blends?
Gasoline burns only when it’s a vapor. Unfortunately, carburetors and fuel injectors don’t vaporize gas; they just atomize it (make liquid droplets). Atomized gas converts to vapor easily in summer heat but needs help when it’s cold. So refiners change to a winter blend with more butane and other lighter hydrocarbons when cold weather arrives. When summer comes, they cut back on those components and return to normal summer blends. This is another reason to use gas for only one season—you’ll always have the proper formulation for the weather.
GETTY IMAGES/DON FARRALL
Is E-85 Fuel the Best Choice in Flex-Fuel Vehicles?
A flex-fuel vehicle is capable of running on both regular E-10 (10 percent ethanol) and E-85 (85 percent ethanol) gasoline. E-85, or more correctly, flex fuel, can have a wide range of ethanol content—anywhere from 51 to 85 percent depending on the season and the relative price of the ethanol and hydrocarbon.
However, because a gallon of ‘typical’ E-85 provides 27 percent less energy than a gallon of E-10 gasoline, you’ll get approximately 27 percent fewer miles per gallon. When E-10 gas prices are high, E-85 may provide some cost advantages. However, since market prices for ethanol vary quite a bit, you’ll have to factor in the reduced mpg to decide whether E-85 is the best choice for your flex-fuel vehicle. Your wallet may be able to tell the difference with the fuel choice, but your car won’t care.
Is Premium or Regular Fuel Best for Small Engines?
Some people fill their small engines with premium gas based on the mistaken notion that all premium gas is ethanol free or that it’ll help the engine run better. In fact, 95 percent of all gas sold in the United States (regular, mid-grade and premium) contains ethanol.
Since most small engines don’t have engine management computers to compensate for different fuels, you should always use the fuel recommended by the engine manufacturer. Believe it or not, small engines generally start and run best with regular fuel.
Can Modern Gas be Used in Old Cars Designed for Leaded Gas?
Tetraethyl lead did double duty by increasing octane and reducing valve seat wear on older vehicles (mostly pre-1970). Later-model vehicles usually have much harder valve seats, so unleaded gas isn’t a problem.
However, if you own an older vehicle, you have three options: Buy a bottle of lead substitute at any auto parts store and add it to each tank (adds about 3? per gallon), have the cylinder heads rebuilt with harder valve seats, or just fill with unleaded gas and rebuild the cylinder heads when they fail.