Car Ownership Advice 1 June 2020

Understanding Different Types of Petrol

No doubt you have been standing in front of a petrol pump thinking ‘should I use regular or premium 98?’.  The days of simply choosing between unleaded and diesel are well and truly over, however understanding the differences between the types of fuel is relatively simple.

What really matters is whether your car is designed for the fuel you are using

Regular, Premium 95 and Premium 98

The main difference between regular, premium 95 and premium 98 is their octane rating, also known as the Research Octane Number (RON).  Octane levels indicate the ability of the fuel to resist pre-ignition or engine knocking. 

The higher the RON the more resistant it is and essentially the more efficient your car will run.

  • Regular unleaded - has an RON of 91 and is the lowest octane level of the three petrols.  It is also usually the cheapest petrol when comparing litre for litre. Most locally produced and Japanese cars are designed to run on regular unleaded.
  • Premium 95 - is the minimum RON rating for premium fuels and is usually positioned in the middle when it comes to price.  Most of the European cars require a minimum 95RON.
  • Premium 98 - this fuel has the highest octane rating and as a result, is usually priced at the top.  Some experts suggest this is the most fuel efficient petrol.

If you have a new car, a fuel with a higher rating may be able to deliver better engine performance and fuel consumption.  However, if you are driving an older model, there might not be any discernible difference.  It won’t hurt you to fill your car up with premium fuel, but it will cost you more at the pump.

E10 (10 Percent Ethanol Blend)

E10 is a blend of regular unleaded with 10 percent ethanol and is now widely available at most petrol stations.  While most cars can run on E10, it is important that you check your model’s suitability before doing so.

Cars and many motorcycles made prior to 1986 are not designed to run on ethanol based fuels and should only use regular or premium unleaded to avoid serious adverse effects for the engine.

At the pump, E10 is usually cheaper than unleaded petrol because it is commonly produced from sugar cane, wheat or sorghum and it’s subsidised.  Although it is cheaper to fill up, E10 can increase fuel consumption particularly when used initially.

If trying E10 for the first time after consulting with your car manufacturer, look out for any unusual noises or pinging, as this can indicate damage. 

E85 (85 Percent Ethanol Blend)

While no damage will usually occur if use different types of petrol, that is not the case with high ethanol blended fuels.  Pumping E85 into a car engine that it is not designed for can cause damage to the fuel lines and other components or simply not start at all.  It could be a costly disaster! 

Not many models of cars are designed to run on E85.  Currently there are only a few including:

  • Holden Commodore V6
  • Holden Commodore V8
  • Saab BioPower models

While E85 might be cheaper at the pump, due to the lower energy content of ethanol, your car will consume more of it than E10 or straight petrol.  It is estimated your car will use 35 percent more E85 than regular unleaded, meaning there are no economical advantages.

Don’t worry about mistaking this fuel for petrol as there is a warning cover on the pump nozzle, which you need to lift prior to filling up!


  • We are seeing more manufacturers making diesel engines in passenger cars, although it is mainly reserved for commercial or heavy vehicles as well as some 4WD.
  • You can fill your car up with diesel at a regular pump or at a dedicated truck pump.  Just check the nozzle before you squeeze the trigger as some have a large neck designed for trucks not your average vehicle.

If you happen to accidentally fill your diesel car with petrol, avoid starting the engine as it will result in costly damage. 


Bio-diesel is a relatively new product and at the moment, is only available for commercial fleets on a trial basis.  It is produced using a mix of tallow or canola oil and diesel.

Before using bio-diesel, it is essential you check with your car dealer or manufacture to ensure it is suitable for your engine. 

If you are still unsure which fuel is more suitable for your car model, speak with a mycar technician who will be happy to advise you on what to use at the pump.

Does your car need maintenance or car repairs?

If your car is in need of a bit of TLC (there is some weird clanging, screeching or just the old girl just doesn't go up hills like she use to), the mycar team are experts in car diagnosis and car repairs, call us on 13 13 28 or find your nearest store.

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