The owner's manual for my vehicle recommends premium gasoline. With premium gasoline now costing 25- to 40- cent more than regular, can I safely fill-up with regular without damaging my engine? The answer is probably yes, especially if you drive conservatively, as you should be doing today.
Many manufacturers of upscale and high performance vehicles optimize their engines to produce maximum power and torque. This includes using higher compression ratios as well as turbocharging and supercharging. Incidentally, turbocharging and supercharging effectively increase compression ratios.
High compression engines require high-octane gasoline to prevent knocking and pinging that can seriously damage engines when it occurs for extended periods of driving. Knocking - that is pre-ignition - occurs when the compression of the fuel and air mixture alone causes it to ignite, thus it is not ignited by the spark plug.
Modern engines with electronic fuel injection, computerized engine management systems and variable valve timing rapidly adjust to different octane ratings to prevent pre-ignition. For instance, antiknock sensors determine engine knocking so the ignition timing is automatically adjusted to prevent knocking.
Because of the capabilities of electronically controlled engines, the experts say that using regular in high performance engines will not cause harm, but you probably won't get the "advertised" performance. For example, 0- to 60-mph acceleration times will be reduced by a second or so. Unless you are drag racing, you probably will not discern the difference.
Even manufacturers of only high performance engines like Porsche, Volvo, and Mercedes-Benz, say using a lower octane fuel should not cause problems. After all, these upscale cars are sold, without modification, worldwide even where premium fuel is not sold. Using regular gasoline should not void warranties, unless, in the rare case, that the manual "requires" rather than "recommends" premium.
You should use premium, if recommended, when carrying a heavy load or towing, especially in hilly terrain. Also owners of vintage muscle cars and other vehicles older than 15 years will usually still have to use premium. These engines don't have electronic fuel injection, engine management systems or knock sensors. If a lower compression engine is knocking or pinging, get a tune-up rather than using a higher-octane gasoline. It could be cheaper in the long run if it prevents engine damage, or uses more expensive fuel.
Using premium in a vehicle that only needs regular is a complete waste of money. It won't add to performance. Premium gasoline will not do a better job keeping the engine clean. Refiners put detergents in all grades. Indeed, the law requires a certain level of detergents in all gasoline.
What about mid-grade fuels? Typically, only two grades, regular and premium, are delivered to most gasoline stations. Other grades are blended from these two at the pump. This allows the need for only two tanks to store fuel. You might try a mid-grade if you want to eliminate minor knocking before filling up with the highest priced premium.
