luxury cars that use 87 octane gas image
MortalGuar
We have a 95 Volvo 850 GLT. The manufacturer recommends using 91 octane gas. But if you are 5000 feet above the level of the sea, you can use 87 octane gas. Why?
Answer
Octane is needed in gasoline to prevent "knock". "Knock" is when the gasoline ignites from compression before the spark fires. Your car runs most smoothly and optimally when the gasoline ignites at the proper moment, not before and not after. Your electronic ignition system chooses the optimal moment and fires the spark plug then. It's less good if the gasoline explodes "accidentally" before the ignition system decides it's the right time.
Gasoline will ignite from compression at a certain pressure that depends on the octane. Higher octane gas will be fine at high pressures where lower octane gas would ignite. An engine compresses the air-gas mixture by compacting it to a smaller volume. That multiplies the atmospheric air pressure by the same as the ratio of the large to the small volume, which is called the compression ratio. If the multiplied pressure is higher than the low octane gas can take, then you get knock. But if you go to higher altitude, the atmospheric pressure starts at a lower pressure, and even when multiplied, it stays below the limit of the low octane gas.
Most "economy cars" have low compression ratios, so that they can use low octane gas even up to sea level atmospheric pressure. They multiply the atmospheric pressure by a smaller amount and it stays under the limit for the low octane gas. But European luxury or sports cars like yours often have high compression ratios.
Octane is needed in gasoline to prevent "knock". "Knock" is when the gasoline ignites from compression before the spark fires. Your car runs most smoothly and optimally when the gasoline ignites at the proper moment, not before and not after. Your electronic ignition system chooses the optimal moment and fires the spark plug then. It's less good if the gasoline explodes "accidentally" before the ignition system decides it's the right time.
Gasoline will ignite from compression at a certain pressure that depends on the octane. Higher octane gas will be fine at high pressures where lower octane gas would ignite. An engine compresses the air-gas mixture by compacting it to a smaller volume. That multiplies the atmospheric air pressure by the same as the ratio of the large to the small volume, which is called the compression ratio. If the multiplied pressure is higher than the low octane gas can take, then you get knock. But if you go to higher altitude, the atmospheric pressure starts at a lower pressure, and even when multiplied, it stays below the limit of the low octane gas.
Most "economy cars" have low compression ratios, so that they can use low octane gas even up to sea level atmospheric pressure. They multiply the atmospheric pressure by a smaller amount and it stays under the limit for the low octane gas. But European luxury or sports cars like yours often have high compression ratios.
If you have a supercharger but dont want to use the pricey gas could you take the belt off and drive without?
Zackary
I was contemplating on putting a supercharger into my V6 Mustang 3.8L and I read that they require at least 91 octane gas but I was wondering if maybe you could disconnect the belt to the supercharger and run regular 87 octane gas until you wanted to actually use the supercharger?
Answer
I'm not real familiar with how a supercharger works, but from what I know, it's not possible. Once you add a supercharger you add on alot more potential with the engine. It forces more air into the cylinders for a bigger explosion, meaning more HP.
Running 91 octane isn't bad. Idk where u are, but diesel cost more where I am. All sports cars, especially high-end ones, run on 91 aka premium. Luxury SUVs also run on premium.
If you stay out of the supercharge range(on turbo cars the turbos turn on at about 3000rpm, once they are on more gas is used). I know a guy who can get a good 25mpg out of his supercharged mustang GT. running 87 really only means less power to the engine.
Does the SC say requires premium? Or does it say recommend premium? If it says recommend, you can run 87 with the supercharger on.
I'm not real familiar with how a supercharger works, but from what I know, it's not possible. Once you add a supercharger you add on alot more potential with the engine. It forces more air into the cylinders for a bigger explosion, meaning more HP.
Running 91 octane isn't bad. Idk where u are, but diesel cost more where I am. All sports cars, especially high-end ones, run on 91 aka premium. Luxury SUVs also run on premium.
If you stay out of the supercharge range(on turbo cars the turbos turn on at about 3000rpm, once they are on more gas is used). I know a guy who can get a good 25mpg out of his supercharged mustang GT. running 87 really only means less power to the engine.
Does the SC say requires premium? Or does it say recommend premium? If it says recommend, you can run 87 with the supercharger on.
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