Higher RON Octane Rating Myth Debunked!

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Heavier Fuel Blend, Better Efficiency, Higher Altitudes, Summary

Contents

Heavier Fuel Blend = Better Performance

Now you hit the nail on the head! Higher octane will not give you more power, but a denser fuel blend will.

This is because a heavier fuel blend has a higher energy density – that means every combustion cycle yields more energy.

Fuels with higher octane ratings may use a denser fuel blend, although this is not necessarily the case. It all boils to marketing, because the fuel blend only changes up to 4% either way.

That’s a maximum variance of 8%. Generally, the variance is much smaller. Take a look at these BP fuel energy density figures, courtesy of Car Bibles :

Fuel GradeEnergy DensityDifference
BP Regular32.53 MJ/LBaseline
BP Premium33.08 MJ/L+ 1.7%
BP Ultimate33.28 MJ/L+ 2.3%

Even the most expensive BP fuel has a mere 2.3% boost in energy density over its cheapest regular fuel. Even that has limited effect because remember, 70-75% of the energy is lost as heat.

So what you would probably get from using BP Ultimate is a 0.7% boost in power (30% of the 2.3% higher energy density).

A heavier fuel blend, therefore, is mainly a marketing gimmick. By using a heavier blend, companies get to honestly tout better performance for their higher octane fuels, which have much higher profit margins.

You will undoubtedly enjoy better performance, just not as much as you think you are getting.

 

Higher RON / MON Rating = Better Fuel Efficiency?

The short answer is – NO. As we pointed out before, the RON / MON octane rating of a fuel is not an indication of how much energy is in it (energy density), or how efficiently it will burn in the engine.

The RON / MON octane rating only indicates how resistant the fuel is to spontaneous detonation when it’s being compressed in the engine’s combustion chamber.

That said, we must point out that the use of fuels with the proper RON / MON octane rating is critical in preventing your car from suffering from poor performance and fuel efficiency.

If you use a lower RON octane rating than is recommended by the car manufacturer, engine knocking may occur. The modern engine will detect that and retard the ignition timings to prevent or reduce the amount of engine knocking. Take a look at this excerpt from a Porsche manual.

However, retarding the ignition timing reduces power and fuel efficiency. How much you lose in power and fuel efficiency depends on how much knocking occurs and how much the timing changes to compensate.

Generally, the greater the discrepancy in RON octane rating and the harder you work the engine, the more you lose in power and fuel efficiency.

In other words, there is no benefit in using a higher octane fuel, but it pays to keep to the car manufacturer’s recommended octane rating.

 

Higher RON Octane Rating For Higher Altitudes

A fuel’s RON octane rating is affected by atmospheric pressure. It actually drops by 1 for every 600 m or 2,000 ft in elevation.

Many people ignore this because they don’t live in high altitude communities, but this can make a real difference in performance and fuel efficiency for those who do.

La Paz in Bolivia, for example, is 3,640 m (11,942 ft) above sea level. If your car uses RON 95 fuel and you pump it full of RON 95 fuel at sea level, your car’s power and fuel efficiency will drop as you near La Paz.

That RON 95 fuel you pumped at sea level would only have an octane rating of RON 89 in La Paz.

By the time you reach La Paz, your car would really be running on RON 89 fuel, and the engine would be retarding its ignition timing to compensate for the lower atmospheric pressure.

 

Higher RON Octane Rating Myth : A Summary

Before you decide if you really need a fuel with a certain RON octane rating, please take out that nicely-printed manual that came with your car and open it up. Look for the page that talks about its fuel recommendation and READ IT.

Note what it says about the car’s minimum and recommended RON octane rating. If only one octane rating is mentioned, consider that as both the minimum and recommended rating for your car.

  • You will achieve maximum performance and fuel efficiency if you use fuels that meet the recommended RON octane rating for your car.
  • Using fuels with higher RON octane ratings won’t harm your car, but it won’t give you any additional benefits either.
  • Using fuels with RON octane ratings that are between the minimum and recommended ratings for your car will give you optimal performance and fuel efficiency at low to normal loads, but will not achieve the engine’s full potential in performance and fuel efficiency at high loads.
  • Using fuels with RON octane ratings that are lower than the minimum rating for your car will reduce power and fuel efficiency.
  • Altitude matters, so make sure you use fuels with higher RON / MON octane ratings at higher elevations.

We hope this article will finally put to rest the myth that a higher RON / MON octane rating means better performance and fuel efficiency.

If you like this article, please feel free to share it out. If you disagree, feel free to comment! Thank you!

 

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