It can't hurt your engine if you use a higher octane fuel. So, for example, if you use 95 or 98 in an engine designed for 91, that's OK. However, it's not acceptable to put in a lower octane fuel than the minimum recommended by the manufacturer. Using 91 in an engine designed for 95 or 98 is potentially destructive.
As long as you never use petrol with a lower octane rating than the manufacturer states then you can mix whatever fuel you like in whatever proportion. In most cars it won't make any difference as they can't take advantage of higher octane fuels.
“Use premium unleaded gasoline with a posted octane rating of 91 or higher. If the octane rating is less than 91, you could damage the engine and may void your vehicle warranty. If heavy knocking is heard when using gasoline rated at 91 octane or higher, the engine needs service.”
When it comes to the different fuel types, it's the number that really matters – 91, 95 and 98. These numbers are called the 'octane-rating', and are an indication of how well the fuel resists burning too early inside the car's engine. Standard petrol is given a 91 rating, while premium unleaded is both 95 and 98.
Yes you can – but only if absolutely necessary! It's not the end of the world (or your car) if it's supposed to run on 95-octane petrol and you put 91-octane in the fuel tank instead – as long as it isn't done often and gets refilled with the recommended 95- or 98-octane in the next tank.
If you notice you've picked the wrong octane at the gas station, there's no need to panic; you can drive your vehicle normally – albeit at reduced power – with lower-octane gas until you have to refuel.
Depending on the car you own, fuelling up with 98 octane can result in increased performance that will see you produce a little extra power when compared to lower octane petrol. But if you're driving something older that hasn't been tuned to run on high-octane, you'll likely see no tangible benefit.
No problem with putting 95 or even 98 in a car designed for 91 – except generally you will be wasting money. Higher octane fuels don't contain more energy. Octane rating is basically resistance to burning under pressure, allowing higher compression ratios to be used (cylinder pressures, actually).
The higher the number, the more octane there is. You will recognise 91 Unleaded as being the regular petrol that users reach for; 95 and 98 are generally seen as 'premium' options, with some petrol stations even offering 100.
Yes, drivers can mix the two types of fuel. The combined gas types will result in an octane level somewhere in the middle — something the vehicle “will survive,” according to The Drive.
You'll most likely notice the spark knock (a sort of high-pitched pinging or rattling noise). Luckily, the engine computers can adjust the timing to limit the amount of damage caused, but you'll definitely notice lower fuel economy and reduced performance in your vehicle.
Premium Gas Vehicles
If your car or truck manufacturer recommends premium gasoline for your car and you put in regular, don't panic. Just because premium is recommended doesn't mean you have to use it; you can easily use regular gas without compromising the engine.
They say that this can cause damage to your motor and possibly the cars computer. "In older vehicles, the engine can make an audible "knocking" or "pinging" sound. Many newer vehicles can adjust the spark timing to reduce knock, but engine power and fuel economy will still suffer," Fueleconomy.gov explained.
If you keep using lower-octane fuel for a prolonged period, you will have a damaged engine and emission control system. But if you use a higher-octane gas than your car needs, it won't do any harm, nor will it benefit your car.
Ongoing use of 98-octane fuel, with the increase in cleaning agents, will help to reduce carbon build-up on the engine's valves and injectors.
Fuels such as 95 or 98 RON (octane rating number) have a higher resistance to burn which indicates higher levels of energy available for the vehicle's engine.
Mixing the 95 and 98 octane fuels will not cause any problems.
98 petrol, which is more stable and resistant to 'knocking', is a better choice when it comes to engine protection. 95 petrol works as well, but if your engine is powerful, it will use higher pressures that 95 petrol may not be able to withstand.
Raising the octane rating (also known as the anti-knock index) doesn't change the energy content of a gallon of gasoline. A higher octane rating indicates greater resistance to knock, the early combustion of the fuel-air mixture that causes cylinder pressure to spike.
Some cars that need premium only need 91 octane, and others may require 93 octane. If the owner's manual indicates premium gas is recommended, you can typically operate the vehicle safely on regular gas. Still, you may not reach the performance and fuel economy indicated in the car's specifications.
These octane level numbers (87, 89, 91, etc.) are a percentage of the fuel's performance measured against pure (100%) octane. Lower octane gas burns quicker than higher octane, and so require less energy to ignite.
At its core, octane rating is simply a scale that defines a fuel's tolerance for compression. The higher the rating, the more tolerant of high compression. High octane fuels don't burn hotter.
No matter what you've heard, premium-grade gasoline won't do more to clean deposits from your fuel injectors or other parts of the fuel system because today's regular gas contains the same detergent additives. The main difference with premium is its octane rating — 91 or higher compared with 87 for regular octane.
If your vehicle calls for high octane fuel, running lower octane can compromise power, reduce MPG, and cause a misfire. Lower octane gas impacts your vehicle's spark plugs and air to fuel ratio in the cylinder, which can damage the engine.
"In most cases, the vehicle will run fine, but you may experience less power and a decrease in gas mileage. In more serious cases, you may hear engine knocking or valve chatter because the fuel isn't burning right.