98 petrol can withstand this, allowing the engine to extract the maximum amount of power from the fuel and run at top power. Click here to subscribe. Using anything higher than your manual recommends probably won't help your car's performance – but using lower might save you a few bucks, Leroux says. So that unleaded 95 also keeps what it promises, the octane number of the fuel is guaranteed by means of an international test procedure (ROZ; research octane number). Yes, you can. Yesterday I accidently fill it up with 40L of 91. This leads to an increased load on the engine. If the fuel flap says ‘premium unleaded only’ it means you need to use at least 95. Compared to 91 octane petrol, 95 and 98 octane generally cost a further 10 to 15 cents per litre; these extra prices can vary around the country depending on location and competition between retailers. If 95 octane petrol is used, those costs rise to around $2,330 per year while using 98 octane fuel would see costs increase again to around $2,410 per year. If the vehicle is designed to run on 91, you're usually best to stick to that as there's generally no benefit in running a more expensive, higher octane fuel. Only cars that are older than 17 years or have trimmed engines need to fill up with 98 unleaded fuel,” explains Daniel Hofer, company manager at Migrol ktip. Welcome to The Globe and Mail’s comment community. But in order for a high-power engine to function, it will need premium petrol which can withstand pressure and temperature. The mixing ratio is then adjusted until the fuel mixture has the same knock resistance as the fuel sample. If the fuel flap says ‘premium unleaded only’ it means you need to use at least 95. It can’t hurt your engine if you use a higher octane fuel. However I accidently topped this with unleaded 98. You may also find the octane specification printed on your gas cap. However, while it’s possible to mix these fuels, experts recommend sticking to the octane recommended for your car, whether 95 or 97/98, to ensure efficient performance and avoid engine damage. About the only time you might need to switch to petrol with a higher octane level is if your car engine knocks (sometimes called pinking) when using the recommended petrol. To display trending posts, please ensure the Jetpack plugin is installed and that the Stats module of Jetpack is active. Unleaded 98 is not a danger for the engine due to the increased knock resistance compared to the usual 95 fuel. If the fuel flap tells you to use 98, that’s what you need to do. Download the new Motorist app now. Then, is it okay if you mix different number of petrol? Thanks. Mobile: *222, Cars - posted in Proton Gen.2: Hey! Whether 95 or 98, depends on the compression ratio of the engine. Then share this post with them! I have a Mazda Axela 2009 2L. This is probably because high-performance engines usually require 98 petrol. If you don’t know what fuel you should be running your vehicle on, seek advice from the local dealer that services your brand of car. Higher octane gasolines are designed to burn more slowly and produce a uniform flame propagation in your engine's cylinder – they're meant for inside a high compression engine where regular gasoline might start burning before it's supposed to and cause engine knock. Your car won’t go any better, it won’t be any faster or run cleaner, the fuel use might reduce fractionally but that’ll be more than offset by higher fuel costs. © Copyright 2020 The Globe and Mail Inc. All rights reserved. Well, that depends on the engine. No votes so far! In a second step, petrol with a knock resistance of 100 is added and a normal heptane (octane number = 0) with a high knock resistance is added. © 2020 The New Zealand Automobile Association Inc. 98 petrol does cost significantly more: for a typical car, filling with 98 petrol can be about $18 more than using 95. This may be true in certain cases, but not consistently. Unleaded 95 or 98? If you put 98 petrol in an engine that is normal-performance, it may even be less efficient because the engine will not be able to completely burn the fuel. This is a space where subscribers can engage with each other and Globe staff. Bartlett says the 2013 Ford Escape with the turbocharged 2.0-litre engine produces 240 horsepower at 5,500 rpm on premium fuel and 231 horsepower on regular fuel. Many drivers who believe that 98 petrol is more efficient think they are saving the environment by using premium. Transport with an open boot – is that allowed? If you are looking to give feedback on our new site, please send it along to, To view this site properly, enable cookies in your browser. I read your post on octanes for high performance engines. That’s a difference of between $80 and $160 per year for no real gain in performance or fuel economy. The octane number of the sample corresponds to the percentage of isooctane in the control mixture. Be the first to rate this post. "I see no benefit in mixing.". Of course, if your car is designed to run on 95 or 98 octane petrol, you must use the octane rating that has been specified by the manufacturer, otherwise you risk causing damage to the engine. However, check your vehicle owner's manual to see what octane rating your engine requires and stick with that. I have a quarter of 91 left. The information about the fuel your car needs is provided in the user manual. If you have a high-performance engine, go for 98 in terms of power. 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