The question of what kind of octane rated fuel is one of those questions many car owners ask. You pull into the gas station and there sits 3 options (excluding diesel). The options are 87, 89 or 91 (also referred to as low grade (87), medium grade (89), and high grade (91) or regular (87), plus (89), and premium (91)) gas. Note that in some locations you may see 93 octane offered instead of a 91 octane.

Some drivers may think that as gasoline is so expensive that just throwing the lowest grade gas into the car sounds like a better plan. However, some people say that the higher grade gas will last longer and therefore be cheaper in the long run. Others tell people to just throw the cheapest gas into the car as possible and that it doesn’t matter. So, which one should you get?

Gasoline Octane RatingsFirst, you should know that octane is and what those numbers mean. Simply stated, octane is the actual element in gasoline that ignites and makes the car go. The higher the octane number is, the more the gasoline can withstand compression before the gasoline ignites. That means that lower octane equals quicker combustion and higher octane has to be heated to a hotter temperature before it ignites.

It is a common misconception that the higher octane level, the better the engine will work. Many think that putting high grade gas into even the oldest and cheapest of cars will make it get better mileage and run better. This is not really true. An economy car will not suddenly turn into a turbo engine if you put 91 octane gasoline in it just like an old truck will not magically get 30 MPG if you put a higher grade of gas in it.

We realize that the above does not explain which level of gasoline is better, or if the more expensive fuel is worth the cost, it illustrates that there is generally no need to buy the higher octane fuel unless there is a genuine need or requirement.

The simplest answer is that it depends upon the car. Some cars are good with regular octane and there is no reason to get a more expensive gas. Other cars have engines that burn hotter and therefore need the higher octane to prevent engine knocking.

Generally speaking, the vehicles that need the regular grade gasoline may be cars like your basic sedans and SUVs. The types of vehicles that may need the mid-grade are higher performance SUVs and the cheap stock sports cars. The vehicles that may need the expensive higher grade gas are cars like high performance sports cars and (oddly enough) a lot of the super gas savers like the Smart Car. However. There are exceptions. For instance, some economy cars need higher grade gas and some sports cars are certified for use of regular grade gas.

The best way to know what kind of gas to put in your car is to read the owner’s manual, look for a label on the inside of the gas door, or an indication near the fuel gauge on the dash.  If there is a manufacturer’s recommended octane level required for your vehicle, it will be indicated in one or more of these locations.

In certain cases, you might find that you have to adjust your octane rating choice based on your own knowledge of vehicle performance. For example, I know of a case of an older Toyota Tundra where the manufacturer recommends 87 octane fuel. However, the engine would sound ‘pingy’ when that fuel was used, and an upgrade to the 89 octane rating solved the engine noise.

Do research before buying a car. If you don’t want to spend extra money on premium gas, then get a car that takes regular. Just remember that paying for the more expensive gas on a car that needs better gas is cheaper than fixing an engine that died because it wasn’t given the right gas.

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