Premium vs regular fuels
 

Hey all,

Wondering if the ZN6 or ZC6 engine performs better with a more expensive fuel like "BP Ultimate" or "Shell V-Power". From research I've done, only sport cars seem to gain a few HP however normal family vehicles gain no benefits.

So is it worth it in a FRS or BRZ?

:thumbsup:

What typically matters from tank to tank is the octane rating of the fuel. Some of the higher end brands have more or better cleaners/detergents in them but most of your mainstream gasolines are of good quality today.

If you're hearing knock/pinging definitely step up a grade, if you're driving hard, step up a grade. I run premium in all my cars, they all require it, when they didn't I still usually ran up a grade. Modern knock sensors will cut in if knock is detected, an easy /cheap way to prevent that is to run good fuel.

If you're not loading up the engine much it likely wont matter.

These are high compression motors and they really should only be run with 91 or higher octane. You may not notice a big performance difference using lower but it's there. You also most likely will not hear the knocking because the computer takes care of it pretty well but it is there and can do damage if low octane gas is used too often. I can prove the performance difference by looking at a chart of my car on fuelly and see a nearly 5mpg drop when I ran a tank of 87 because it was all that was available when I needed gas once last year. All other parameters were the same other than that one tank. In hindsight I should have just put in a gallon or two but was so used to filling the tank I just did it.

How is this even a question? read the manual. It will tell you what you should and must use.
The octane levels are for reducing knock ONLY! Higher octane fuel does not give you more power really. What it does is allows the engines with learning ECUs to adjust the timing higher. This is where the "more power" is created.
As a society that identifies higher numbers as being stronger or better I think many people totally misunderstand octane rating. High octane fuel is intended to reduce preignition in high compression engines it is not stronger or better than low octane fuel in any other way. To grossly over simplify what is happening the higher the octane fuel the harder it is to ignite not the other way around. Sure you can run high octane in a regular engine but it is not doing a single thing for you. You should not run lower octane in a high compression engine though since you run the risk of damage. New engines with self adjusting timing this risk is not huge but run too low in an older engine and you better be good at fixing it.

In the words of Tai Lopez, "Knawledge."

And cleaners/detergents are a separate issue, they are about preventing/removing carbon buildup in the intake system, especially on intake valves (unless the engine uses direct injection, then of course fuel detergents can't clean the intake valves because the valves do not come into contact with fuel).

Cleaning capability is per se indepent of octane rating, though some brands put more cleaners in their premium (high octane) fuels.

Cleaners/detergents also have no effect on HP, at least not directly. I mean, if there were no or insufficient cleaners, gradually carbon buildup would interfere with engine operation and reduce HP, but that's not the effect the OP has in mind, I suppose.

All gasoline is supposed to contain cleaners, there are standards for that. But - at least in the US - some gas brands set their own higher standards: "Top Tier" gas.

The use of the words "regular" and "premium" don't help the misconceptions either! Premium implies that it is somehow better overall which is not the case.

You bet that's an example in a marketing text book somewhere...

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Strangely enough that price difference is yet another thing that makes people think the higher octane is "better" fuel. We are conditioned to believe that if we pay more for what we think of as the same thing then it must be a higher quality. There is much more to the price difference in fuels than quality. Although "premium" does have a few additives that cost a bit more to produce these are not really what drives the price up. The regular is made, stored and transported in massive volumes and this keeps costs down. Since premium is made in substantially smaller volumes then those costs get driven up.
If you pay $10 to make, store and transport 100 gallons of regular fuel and sell it for $1 a gallon you make $90 for your $10 investment.
If you spend $10 to make, store and transport 40 gallons of premium and sell it for $1 then you only make $30 for that same $10. In order to show a better profit you need to charge more and this is why they do. The oil companies make way more money on regular fuel sales then they do with premium so trying to upsell you really makes no sense.
(To all you economists out there I know my comments are way oversimplified but was going for brevity not 100% accuracy)

It all depends on the OEM tune. The FR-S and BRZ were tuned by factory to use 93 octane under North American rating. I think for you in Australia your system rates that as 98 or 100?

Anytime you use something below factory settings, the computer will detect that because the fuel will start to detonate when it's not supposed to. The computer will detect the explosions and compensate by lowering the compression and horsepower to prevent more premature detonations. So it's not so much that you gain power by using the factory recommended fuel, you lose power by using the cheaper fuel.

If you put something with higher octane and more expensive than the recommended fuel, the computer has no way of knowing that. You will still get the same 200 horsepower on 100 octane that you get with 93 octane. You would just be wasting your money on more expensive fuel with no added performance.

The reason why family cars get no benefit from premium fuel is because they are usually tuned to 87 octane. And if you decide to put 91 octane in your Corolla, there is no way for the Corolla's ECU to detect that. And you would be wasting your money again.

You gotta check the factory specs for each car though. Some sports cars like ours and I think the STI are tuned for 93 octane. Most are probably tuned for 91. An accord coupe V6 6MT is only tuned for 87 octane.

Yes ............ :)


humfrz

well...around my area there is only 91,,and i use 91 shell V power...

I hope thats fine =[

Manual says: Recommended 93 Required minimum 91. All is good in the world.