Should you put premium fuel in your consumer car? Would you get more bang for your buck?
Each car has an octane number recommend by the manufacturer. If Mazda took the time to write 87 for its naturally aspirated motor, obviously the engine is made to run on 87 octane. However, The Speed3 needs 91 minimum.
The difference between regular gasoline, the better and the supreme is mostly the octane rating. The “super” or “supreme” type of petrol simply contains more octane per sip.
Why Higher Octane?
Now, perhaps you wonder what is the octane? Simply said, it is an anti-knock. Why would you need that? It is used to increase the capacity of a gas to be compressed before exploding by single compression. Why would you put supreme in a motor vehicle? The timing of an internal combustion engine is calculated in a very precise way. If the engine compression is too heavy for the compression capability of the air/fuel mix that is injected, then the explosion in the combustion chamber tends to disrupt the timing by causing the crank to turn quicker.
The reason why a turbo or high compression engine produces more HP per litre is that it forces a higher pressure on the mixture, which detonates with a bigger bang (as it is in a confined space).
By increasing the octane level, it allows the turbocharged (or high compression ratio) engine to compress a lot more air/fuel mixture before it explodes by itself.
Only then do you retain control over the spark plugs which are activated at the optimal time, depending on the position and rotation of the crank.
Therefore, instead of putting premium gasoline in a normal car, you could set your money on fire. After all, the end result is the same.
Adverse Effect
In theory, if the 87 octane ECU map is intended for 87 octane at 30 degrees Celcius, putting with 91 in these conditions is effectively useless and a total waste. Future cars will probably have an option for that, but it’s not for tomorrow. In the old days, you could lower the compression ratio to somewhere around 9:1, then maybe the higher octane fuel could be used. But ultimately, in today’s overcomplicated engines, there would be loss of HP with the 91.
Finally, the 91 being the high end of several oil (although you can sometimes find 94), I suspect, without evidence, that some additives are brought into the mix such as injection cleaners, lubricants and for the winter, a mixture that is less likely to freeze. This leads be to believe that the 87 tank, being the most popular, is refilled by the station on a more regular basis than the 91. Therefore, you are more likely to pump old gas when choosing the 91, especially if the station is not busy.
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Tags: 91 octane, higher octane fuel, octane booster, save fuel
Leave A Reply (2 comments So Far)
mike
430 days ago
I’ve always noticed a better performance and mpg difference using 91 over 87 straight from the gas station or by use of additives. By my calculations I waste money by not using 91 or better octane fuel. Let’s say for example with 87 I get 26mpg and with 91 I get 29mpg…just to show the difference let’s use 100 gallons. With 87 I can go 2600 miles and with 91, I go 2900 miles. That’s a difference of 300 miles.
Consistently, 91 is $.22 more than 87 so let’s go with 87 at $3 and 91 at $3.22. That would make it $300 vs $322 to make up the difference of 300 miles I would need 11.5304 gallons at $3, which would be $34.61 so it’s only a $12.61 savings you would also have to account for the better performance and cleaner engine and the other related parts that will be affected. Therefore, premium is exactly $.12 cheaper; divide the savings by 100 gallons.
Wow, is that right or is my math incorrect?
bob
428 days ago
About those MPG figures (26 and 29), would those come from your on-board computer?