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26

It's not a problem mixing them. Just start using 95 if that is what the engine calls for. You'll not create any issues doing so. Modern day engines have sensors which can adjust for the fuel. If yours calls for 95, but you're running 92, the engine most likely won't be putting out the power it would on the 95. You probably won't notice a difference in ...


21

Realistically, if the manual and the manufacturer are stating you should use 87 octane, that's really what you should use. If you purchase more expensive 89, 91, or 93, you are just wasting money. The higher the octane rating, the harder it is for fuel to burn (or ignite). If the vehicle was specified to use 93, then that's what you should buy or you risk ...


11

Presumably since you say "92 octane gas" you are not in Europe. The whole topic is a mess, because there are different scales for measuring "octane". The most common scale world-wide is RON, but there is a different scale known as MON which produces lower numbers, and in some countries (particularly the USA, Canada, and Brazil) the numbers on the pump are ...


10

Octane rating is a representation of how much fuel can be compressed before before it explodes on it's own. The action of the fuel igniting spontaneously due to excessive pressure causes what mechanics refer to as knocking or pinging. Knocking has the ability to do some real damage. So avoiding it at all costs is a very good idea. Sometimes, knocking can be ...


7

It means "at least". You will not cause any damage by using the higher octane fuel. The reason for the RON 95 rating in the first place, this is the lowest octane rating you can run before you might start hearing pinging or pre-ignition.


6

Premium will last longer sitting in a tank. Chevrolet recommends premium for the Volt for this very reason. According to Volt Vehicle Line Director Tony Posawatz (as quoted by gm-volt.com): If people are not using the extended range capability a lot, the premium fuel does last a little longer,” he said


6

I can get you halfway; here's the formula for the effective compression ratio of a forced induction motor: Effective Compression Ratio (ECR) = sqrt((boost+14.7)/14.7) * Static Compression Ratio (SCR) So, for 5psi on your 9.9:1 SCR motor: ECR = sqrt(19.7/14.7)*9.9 = 11.46:1 However, I have had quite a difficulty trying to find a good way to get ECR to "...


6

If the manual says that 95 octane is suitable then the car will be fine with 95 octane. 98 will only yield appreciable performance gains if the ignition advance is being actively limited by engine knock. Since both engine and tune are set up by the manufacturer to handle 95, the impact of using 98 will be limited.


6

In current fuel injected vehicles, the computer (ECU) adjusts for it. There are sensors in your engine called "knock sensors". When the sensors start picking up a knock, it will pull timing. Usually, timing is advanced where it sparks to fire the engine before the piston reaches top dead center of the compression stroke. This is the start of the power stroke....


5

You have nothing to lose on a modern engine (except power) Any engine with a knock sensor and computer-controlled ignition timing (e.g. modern fuel-injected designs) should be able to alter ignition timing to minimize the risk of detonation. When ignition timing is pulled, you should be able to feel loss of engine grunt. Here's how the sequence of events ...


5

Mixing 95 octane gasoline with 92 is perfectly fine. In fact, this is what many gas stations do in order to offer their mid-grade product. For example, many gas stations in the United States offer 87, 89, and 91 octane gasoline. The 89 octane gasoline is a 50-50 mix of 87 and 91 octane gasoline. Mixing grades of gasoline will not harm your engine as long as ...


5

There is no such thing as an octane sensor. Octane is analyzed in two ways. Analysis of the chemical composition, they call this Research. They place the fuel into a test engine and run it until it pings, they call this Motor. If you look at a gas pump it will usually show for example, 87 octane (R + M)/2. This is an average of Research and Motor. A modern ...


5

One of the reasons that a turbo setup with the equivalent effective compression is more forgiving of low octane gas than than a static compression setup is that you're not at that compression ratio all the time. Take that honda, for example. At 9:1 static ratio, you can run 87 octane all day as long as you don't push any boost at it. When you do start ...


5

As Zaid said, if the manual says 95, use 95. Simple as that. Actually, using a higher octane rating is not ideal, whatever it may seem. From whatcouldbegreener.com: What will happen if I use higher octane gas than I’m supposed to? A few things. For one, you will be wasting a huge amount of money paying for high octane gasoline. Second, your car ...


5

There are different ways to measure the octane number of a fuel. Europe uses the RON method. Research Octane Number (RON) The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results ...


5

"Higher octane" only means more knock-resistant. It does not mean "harder-to-ignite" or "hotter burning." A gasoline engine will not perform worse in any way on higher-octane gasoline. The higher-octane outputs of a gasoline refinery have only been reformed to be more knock-resistant. They still have to meet the same volatility, detergent, oxygenate, and ...


5

A modern car (say, post-1995) will run on lower octane gasoline with reduced performance (power, economy) and no other issues. Older cars did a lot of nasty things ranging from occasional "pinging" or "ringing" noise and accellerated engine wear to complete engine failure. Then again, one cannot easily find these days neither a pre-1995 car nor a gasoline ...


4

The acid test is if you try a lower octane fuel, if you hear any "knocking" sounds under hard acceleration (perhaps up a hill), then you definitely need a higher octane rating. As Paulster2 mentions, there will not be any performance improvement, in spite of what a lot of people say. The octane rating is just a measure of resistance to knocking. I have a ...


4

In the case of topping off, it would make absolutely no difference other than costing you more at the pump. Octane is a rating which would indicate how hard it is for the fuel to burn. The higher the octane rating, the harder to burn. If anything, leaving gasoline for longer periods of time is going to make it harder to burn, thus effectively raising the ...


4

Using a higher octane fuel should not have caused the SES light to turn on. The only fill-up-related thing I can think of which would cause the SES to turn on is if there is a bad batch of fuel (something like water). In such a scenario, the SES will be triggered due to the engine knocking. This would be typified by engine sputtering, and is usually ...


3

Generally, you're best off using the fuel recommended by the manufacturer. Octane rating is a measure of how resistant the fuel is to ignition. The higher the octane, the harder the fuel is to ignite. Fuel that is harder to ignite allows higher compression ratios and more agressive engine tuning. If the fuel is too low octane, modern engines will detune ...


3

This claim is my opinion. I have no facts to back the claim. This could even be urban legend I've read a plethora of articles recently, due to this question, regarding this subject. It seems to be the consensus of some somewhat reputable sources that manufacturers will do testing with the lowest grade fuel to ensure that the vehicle does not knock/ping/...


3

To answer your question directly, adding the 95 to the 92 in your tank will not cause any real problems, in the short term. Once you have used the tank full you can carry on filling up with the recommended 95. Modern engine ECU programming will adjust the timing of your engine, knock sensors, to minimise or prevent engine 'pinking' caused by the lower octane ...


3

Addressing the question from the point of view of a chemist: this sounds highly implausible. Evaporative distillation is not terribly efficient to begin with, even with very different chemicals. I.e., even if you have two miscible liquids with very different boiling points, it can take a number of evaporation-condensation cycles to achieve significant ...


2

Here's the deal : higher octane means less volatility, and this is meant for engines with higher compression so that the fuel doesn't ignite too early in the cycle . Lower octane fuel is more volatile and is meant for engines where compression rates are lower, so that the ignition in the cycle not occur too early . In all cases, follow the manufacturer's ...


2

If the specs call for 91 octane, use 91 octane. Using higher octane fuel will not give you better performance. Only engines which need the higher octane will see better performance from the higher octane. In most cases, engines which should use the lower octane will get worse gas mileage from the higher octane fuel.


2

Having a live scan running is by far the easiest way to tell if the ECU is pulling timing while the engine is running. Beyond that, you need to be aware of what the manufacturer's requirement for an engine is, such as it's performance level. Several situations which call for higher octane: Turbo/Super charging High static compression ratio (10+:1) Both of ...


2

The ECU(or at least the better ones) can indeed actively 'search' for the point of pinging as you said. The pinging sensor listens to the combustion, based on that the ECU determines how close it is to knocking. Real, actual knocking is audible even to the untrained human ear, but knock sensors can also detect near knocking situations. And that is the most ...


2

87 will work, 89 is optimal, 93 will also work but uses a bit more (will start to run leaner but the computer easily compensates but using more fuel) 87 better for winter (no difference over 89), 89 better for summer (helps when underhood is HOT when you have the A/C running AND trying to keep the engine around operating temp. I would maybe avoid the ...


2

According to what I'm reading, the Axela is another name for the Mazda-3 we have here in the states. There are two engines offered for the vehicle: 2.0L & 2.5L. Both engines only require "regular unleaded", regardless of transmission type. I don't believe either of these engines are turbocharged from the factory, so there's no forced induction ...


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