High octane will most likely cause lower fuel mileage and reduced power sicne it effectively retards ignition timing. However, modern cars are open loops FI systems with O2 sensors, so they can alter the maps to soem degree dependign on fuel grade and a variety of environmental conditions, but the primary map is still optimized for 87 octane, 60-70 derees, low altitude and moderate huidity. They represent the mosts common dirivng siutations. Even on long trips, my mileage will typically drop by as much as 20% under 50 degrees. The engine just cant; run as super lean in those condidtions without predetination.
Also consider that premium gas is used less often by most drivers, therefore the tanks at the startions have a slower turn over. ON my motorcycle, if I'm in BF on a long tripE at a little hick station, I rarely get premium becasue they tend to only turn over those tanks on yearly or less basis.
What is the point?
There is no advantage to running high octane fuel in this type of car and most likely will cause reduced performance and mileage. Race fuel and aftermarket exhausts often have the same effect.
the original question was whether there isa difference in output for the internal combustion engine,
the average modern(I am ****uming) including those designed
only for
and those like the 03 corolla(which will accept different Octanes)
the amount of actual energy ultimately transfered into kinetic
energy of the auto in motion for the higher grade.
And yes in my opinion, the higher octane has higher yield
and that is why mercedes prefers to design it around the premium
grades. Of course, if the mercedes engine cannot take lower grades,
we cannot compare. But my ****umption why mercedes prefers
the higher grades is probably close.
Sorry, but high hoctane does not contain more energy per unit volume of fuel. The primary difference is the burn rate and stability. Higher octane fuel in more stable, ignites slower, but burn quicker. The total energy output is similar to lower octane. High octane is needed for high compression engines and those with more aggressive am profiles or advanced ignition timing. Honestly in most casrs, the diffeence between running 87 and 93 is not dramatic, but the differnece between 93 and a 107 race fuel is... as well as other additives.
IF I'm not mistaken, OCtane is the ratio or quantity of Octane is the fuel as compared to the other indredients of Hexane, Pentane, and Ethanol, Methanol, detergents, stabilizers, and other additives and process catalists.
I will agree that cheap gas is also bad. Typically the major brands (BP, shell, Exxon, Ctigo) sell their CIP (clean in place, fuel fro mthe next batch is run to pruge out the lines and either sold off as such or reused in a different part of the process) rinse between batches of fuel to the independents at a discounted rate. Although thsi fuel meets teh state and federal minimum rewuirements, it's of lower quality in general.
Guest eric95tt
I'm sorry but if your run 93 octane in your corolla and think that is all there is to good performance and mileage then I have the new and improved turbo vortex mod to sell you. It's a great little fan you stick in your intake and it boosts performance by 100%! Mileage by 50%!
To state that there is some mAssive coverup because a car here and there has lasted 100's of thousands of miles running premium fuell is ludicrous. There are so many other factors that go into the performance, reliability, emissions etc of a car.My sister's 1986 sentra went over 30000 miles on its ORIGINAL oil. I guess that means we do not have to change the oil in our cars either, particularly if you own a Nissan Sentra. Wow what a breakthrough. Damn the manual! Her car is proof enough.
Read the damn manual. It tells you precisely what octane is required for your car, the octane it was designed for. If you want to go on believing silly myths then by all means do so.
man, I can't believe this discussion is still going on.
This octane rating system is a ploy by the oil companies
to reap more profits from types of gas where they put
very little "extra" according to an accountant in the industry
who remains annonomous.
Why don't the oil companies use BTU's or Calories or Joules
of energy output per litre from a typical test engine for different
grades of gas ?? "Octane rating" is confusing on purpose
as I have found out that there is no strict regulation on exactly
what this means.
Also, from what I have read so far, the ethanol additives
actually decrease energy output from a gallon of gas since it has
less(mileage or power) per volume. ie you are getting ripped off
although very slightly.
We just need a corolla test vehicle on one of those machines to measure
the difference in performance with different grades of gas.
My feeling is that the oil companies put something extra in these
higher octane but it is a rip off compared to what extra you have to pay.
this is my last post on this topic. it is a tired horse.
The bottom line is that the Corolla does not need and does not benefit from using high octane. If you beleve it does, then I want to see some dyno results or an objective scientific study not wishy washy cause and efect statistics. But any reputable engine tuner/builder will tell you the difference between the 2 fuels.
In order to get better milege, you engine needs ot make more torque through the "cruising" RPM range at low throttle positions while using the same amount of fuel. High octane gas will not do this for you. It might possibly give you a very sligth increas in proformance at hgih revs and mae the engine feel like it's running smoother (ignites later). Frankly, if you use a fuel that makes less HP, you typically will reduce engien wear and increase durability because the engine will be less stressed.
If your mileage is low and you think you NEED high octane fuel, you should try greasing your brake rotors and also check your exhaust bearign while you're at it. 
Guest plmaramba
Greetings from the Philippines!
I own a '93 Corolla 5-Speed/Manual, as per my car manual an Octane Rating of 95 is to be used (compared to New Zealand it's 91- still from the manual). Why
is this so, as there in the States you still have an RON of 87?
Best Regards,
Pete
They may use a different grading system in NZ. They also have whats called "reasearch grade" in the US which I belive is a higher number. NZ may also use a different testing standard or test method.
