Gas??

[downshift]

i been wondering....everytime i pull into the gas station, i wonder about putting mid grade or premium into the car. My question, would i feel the difference if i put mid grade(91) or premium(93) in my car? I put mid grade before and i dont believe i noticed much of a difference....so i was just wonderin.

[gounc14]

No.

[downshift]

lol thanks....

[[Zero-S]]

You would only feel the difference if you bumped up the timing to where you needed to run premium. (I.E. my dohc KA)

[SeVa-S13]

I noticed a difference, as did Zach. And I only go to BP.

[240Knightrider]

you feel a difference. If you dont pay more attention. Not trying to be mean. Its not going to be obvious but just pay attention to your rpms and mph and the sound. It changes.

[D1SR240]

I thought that the higher the octane, that just meant it can handle more compression, how does higher octane help hp?

[MainEvent212]

eh...not quite

higher octane resists detonation more...

this is good in high compression and turbo application

[Ubernoober]

An Octane rating is determined by chemical comparison to a blend "fingerprint" and mechanically in a knock-motor. The two results are averaged to give the final octane. This is the R+M you see on the pump. "research + mechanical" or somesuch."Octane" for gasoline really comes down to a rating of the fuels ability to RESIST detonation. The higher the octane rating the more difficult to get it to combust, ergo the ability to run with more timing or higher compression.If your car did not ping or rattle on regular, there will be no noticeable gain by going to a higher grade without altering anything else. You could in fact lose mileage. If on the other hand, your timing is advanced enough or your compression high enough, you can gain by going to a higher grade. This was taken to a bit of an extreme in the early 70's with cars coming off the factory floor requiring 103 octane and running 12:1 compression ratios. You can gain engine efficiency by going to higher compression ratios.

As an aside, mid grade is usually just regular with additives, while premium is a completely different blend. In other words, buy regular or premium since the mid is not truly superior to regular. Every gas company is different though.

[crzycav86]

Actually.. doesn't the owners manual ask for premium? IIRC, the car is tuned for premium gas, but when you add regular, the knock sensors compensate and thus performance suffers. So in a way, you will have more power with the good stuff.

[Ubernoober]

You are correct, but as our cars age, some will lose the benefit of running premium for any number of reasons. I just didn't want him to think "premium=better=more power" because that simply is not true. Particularly not the bigger explosion stuff.

[elbles]

The ONLY advantage to running a higher-octane gasoline is the resistance to detonation. Octane refers to a hydrocarbon chain with 8 molecules of a certain other molecule (it's been well over a year since I've done anything with chem, so forgive me if the details are out, heh). For gasoline-related purposes, it is solely a measure of how much the gas can be compressed without premature ignition (knock, as it is also known). There is actually MORE energy in lower octane gasoline, so if your car is not designed for higher octanes, like the KA24E 240's are (they love 87 octane), just run the cheap stuff . . . you won't miss any performance, and you'll see an increase in gas mileage over 89 octane even (I noticed a difference of 2-3 MPG under the same driving conditions when I wanted to experiement with it).

[downshift]

good info in here....

[Radian]

Yeah, I think you only really need to use higher octane if you get knock with 87.

[Chingon]

The ONLY advantage to running a higher-octane gasoline is the resistance to detonation. Octane refers to a hydrocarbon chain with 8 molecules of a certain other molecule (it's been well over a year since I've done anything with chem, so forgive me if the details are out, heh). For gasoline-related purposes, it is solely a measure of how much the gas can be compressed without premature ignition (knock, as it is also known). There is actually MORE energy in lower octane gasoline, so if your car is not designed for higher octanes, like the KA24E 240's are (they love 87 octane), just run the cheap stuff . . . you won't miss any performance, and you'll see an increase in gas mileage over 89 octane even (I noticed a difference of 2-3 MPG under the same driving conditions when I wanted to experiement with it).

so you are saying low octane fuel has a higher BTU rating than high octane....(this i did not know)..

[MOE101]

errr...I am still a little confused

so your saying the ka24e is ok with 87, but the ka24de should get premium?

[SilviaS14KA24DE]

that soudns right because kad24e is only single cam

[elbles]

Chingon: Yeah, that should be right. There are more BTU's in lower octane gas, so in an engine not designed for it, it will offer the same (if not better) performance, along with higher fuel economy. In such an instance, the lower octane fuel works with the lower compression engine to yield the most efficent combination. In a higher compression engine, a higher octane fuel is necessary not only to resist knock, but also to yield maximum efficiency; due to the engine's higher compression, more energy can be extracted from each firing, which can certainly help negate the fact that less energy is present in each molecule of a higher octane fuel, usually to the point where equivelent high compression/low compression engines will acheive the same MPG running the appropriate high or low octane fuels.

MOE101: I know the KA24E is a lower compression engine, and 87 is all it needs. For the DE, I think the compression is slightly higher (could easily be wrong there though, heh), though I doubt it was to the point where a higher octane fuel would be necessary. Hope that helps . . .

[elbles]

Oh, and for the people who don't know what a BTU is: it's a British Thermal Unit, usually applied to items such as air conditioners, but being a unit of energy, it can also be applied to other things as well, especially anything that burns. :-)