What Fuel Should I Use In My Car?

Fuel prices have been skyrocketing lately, and like the entire world, Kiwis are feeling the strain when filling up. It can be tempting to use the cheapest fuel on offer, however it is not always a good idea. 

To understand more about the best fuel suitable for your car, let’s look at the different fuel types, how they affect your vehicle, and what you should do if you use the wrong fuel type.

Which fuel should I use?

Before you stop by a petrol station to fuel up, you should be aware of the manufacturer's fuel type recommendation for your car. In the past, car owners only had to choose between diesel and petrol. Now, with evolving technology and the demand for eco-friendly fuels, a few things have changed.

 How to Know Your Car Fuel Type

To find out what fuel is recommended for your car, check the user manual or the sticker displayed inside the petrol flap. 

Different Types of Fuel

New Zealand uses RON (Research Octane Number) to rate the fuel octane value. The most common types of fuel include:

1. Standard unleaded petrol (91)
With an octane rating of 91, most cars on the road will be fine using this standard of fuel. However, considering this fuel has a low octane rating, it should not be used in higher-performance vehicles.

2. Premium unleaded petrol (95)
This petrol type is designed for higher-performance and most hybrid vehicles, and provides a smoother engine operation that improves performance. It has an octane rating of 95 and is more expensive than the standard 91 petrol.

3. Premium unleaded petrol (98)
This fuel has a 98 octane rating making it the more common top-of-the-range octane unleaded fuel (though some petrol stations offer 100 octane fuels). It provides higher engine power and is mainly used in performance tuned cars.

4. E10
E10 fuel is an ethanol blend. It's 90% unleaded petrol and 10% ethanol. Additionally, it has an octane rating of 94, which offers better performance for your car — e10 is a common substitute for 91. However, E10 is less energy dense and doesn't offer the same fuel economy compared to other unleaded fuels. Please note, try not to spill E10 fuel on the vehicle paint as it can cause damage.

5. Diesel 
Diesel is more energy dense than unleaded fuels, which typically implies that it's more fuel efficient. While diesel is also cheaper than petrol, diesel vehicles are usually more expensive to buy, and you’ll also incur additional costs like Road User Charges (RUCs).

My car takes 91, can I use other fuels?

Yes, you can use a higher octane fuel — just not diesel. Some retailers will talk about the benefits of premium fuel, and you can use 95, 98, or E10. Higher octane fuels will cost more, and the cost may outweigh the benefits, especially if you are not a conservative driver. 

My car takes 95, can I use other fuels?

The simple answer is no, not anything less than 95. You can use a higher octane fuel, but anything less can cause mechanical damage to your engine. Higher octane fuels are recommended for turbocharged and hybrid engines because they increase the compression ratio. 

Unlike naturally aspirated engines, turbocharged engines function by forcing additional air into the engine. With more air forced into the engine, you'll need higher octane fuel to increase combustion strength. As a result, the engine will produce more power and improve overall fuel economy. 

An excellent example of a turbocharged engine with power and fuel efficiency is Suzuki's BoosterJet system. It uses cutting-edge technology to deliver the desired torque without hurting the environment. The reason higher octane fuel is more expensive than 91, is that the higher quality fuel used to boost octane costs more to produce.

Can I mix fuels?

It is okay to mix fuels (except for diesel) in your car as long as the octane rating is not less than the recommended fuel you should use. For example, if you have a car that takes 91, then mixing with 95 is fine, but not the other way round. A car that takes 95, can only mix with fuels that are higher like 98. Diesel cars can only take diesel.

There are benefits to being consistent with the type of fuel you put in your car, so once you decide, try not to chop and change.

What to do if you use the wrong fuel type in your car

The type of fuel you use in your vehicle can determine if your engine runs at peak performance or breaks down. 

Your engine operates in low-optimal conditions when you run on lower-octane fuel than what your manufacturer recommends. Consequently, you experience fuel knock, which can damage piston rings, exhaust valves, and the piston itself.

If you accidentally fill your 95-octane tank with 91-octane fuel — stay calm. There's no need to drain your tank but avoid fast driving. Additionally, ensure you fuel with at least 95-octane fuel grade petrol as soon as possible. If you can top up with 98 octane, all the better, as this will increase the overall octane rating of the fuel in your vehicle.

Suppose you fuel your diesel car with petrol, or petrol car with diesel:

• You should not start your car; if you start the ignition, fuel will circulate within seconds and cause damage to your engine and the fuel system.
• Look for tow truck services nearby to take your vehicle to a garage. 
• At the garage, the mechanics will flush the fuel from the fuel system, and your vehicle will be ready to hit the road without mechanical damage.
• Finally, notify your insurance as soon as you can. 
  
  

Signs that you’ve filled up with the wrong fuel

You can easily notice if your petrol car is running on diesel fuel or vice versa when you experience the following. 

• a loud knocking sound while accelerating
• your engine misfiring
• excessive smoke coming from your exhaust
• slower than usual acceleration
• the engine warning light illuminating
• the engine stopping altogether
• your car struggling to restart 

Remember, if in doubt, check your fuel flap before filling up and take it easy when you drive. That way you’ll get the most out of the fuel you do put in and avoid any costly mistakes.

If you need a fuel-efficient car that doubles up as eco-friendly and easy to use, you're in the right place. Suzuki has cutting-edge engine technology paired with lightweight compact design to ease pressure at the pump and enjoy your daily drives. Check out our detailed Guide to Buying a New Car to get you started.