Gasoline Fuel questions...

[mkeomec]

I was wondering if there is any proof that different gasoline companies and different grades (octane ratings) affect the performance in terms of mpg and power, and the engine wear.

The only reason i bring this up is because i've noticed differences in my GT between gasoline companies (ie. Chevron is better than Arco) and also octane levels (91 is better than 87) Of course on the GT-S, 91 is needed, but i have 87 octane in my GT and i swear i don't get as much power. Is this bad for my engine as well? I think i get better mpg with higher octane, but it could be psychological... Thanks

[F35-JSF]

91 is going to burn cleaner so you will have less deposits left over not to mention better running and better mpg.

[vvtlikick]

As far as I know noone has ever done a careful comparison of different octanes in the GT. So, you can be the first :gap:

[nxracer]

The GT computer is tuned for 87 octane, running anything more is just a waste of money.

[XYRCNCP]

Originally posted by nxracer
The GT computer is tuned for 87 octane, running anything more is just a waste of money.

:werd:, I've been driving loaners for the past 2 weeks and I'm telling you, it's a blessing to use 87 instead of 93.

[F35-JSF]

Originally posted by XYRCNCP
:werd:, I've been driving loaners for the past 2 weeks and I'm telling you, it's a blessing to use 87 instead of 93.

Sole reason I sold my TA:D

[XYRCNCP]

I've drove a RAV4 last week, and this week I'm driving a Camry LE, both with the 2.4L 4cyl that's gonna be in the tC, pretty nice engine, and good pickup, even in the Camry.

[F35-JSF]

My friend said the same for the new solara 4 cyc he rented.

[JohnnyWash1]

Originally posted by F35-JSF
91 is going to burn cleaner so you will have less deposits left over not to mention better running and better mpg.



Where did you get this information? Do you have a source? A higher octane only indicates a higher resistance to burning, so that the fuel will not ignite itself in high heat/pressure situations as easily as a lower octane rating. As a side note, all grades of gasoline are required, by law, to carry the same amount of cleansers and detergents in them. The names are pure marketing manipulation ("supreme" vs. regular?--c'mon, how obvious).



Jon

[Tung]

91 should be safer then 87 if you have a high compassion enigne, I think the lower the octane the more oputunatity to have the gas burn before spark.
Please forgive my spelling...

[aerospike2002]

Any gasoline is better than Arco....that's bottom of the barrel junk. Only poor college students use it.

I use Unocal 76 because I feel it has all the same benefits as Chevron, but without the ridiculous price.

I've always used Unocal 76, and when I first asked Mike Stafford what type of gasoline he prefers for my turbo GTS and also for his turbo vehicles in general, he also confirmed that he uses Unocal 76 whenever possible.

Unocal 76 has ProPower which, IMO, is just as good as Chevron w/ Techron.

[voidhawk]

Brand-loyalty only makes the advertising execs richer. Think about what you are really paying for (better gas or better advertising?) then decide where to spend your money.

[JohnnyWash1]

I use Shell because it is what Ferrari uses. Call it stupid, but we all have our reasons.



Jon

[F22-Raptor]

I use Sunoco since they don't use Middle Eastern Oil :D Or is it Mobil. As far as octane goes using 91/93 in the GT will allow the engine to advance timing to the fullest. But it is tuned for 87.

[treeh8r]

Quote, "Chemistry of the Environment", pg. 179:
Knocking and Octane: Combustion is a radical chain process, similar to...that allows the oxygen to combine very rapidly w/ the fuel molecules. The spark-ignition engine of automobiles works by igniting a mixture of gasoline and air w/ a spark. The air/fuel mixture is first compressed by a piston in a cylinder, then ignited. The spark fragments the fuel molecules in its path, generating enough radicals to set off the chain reaction. The force of the explosion on the piston delivers power to the drivetrain. The greater the degree of compression, the greater the power. However, the compression stroke itself heats the fuel; at sufficiently high temperatures, the fuel molecules can fragment spontaneously, setting off the explosion prematurely. Pre-ignition lowers the power generated and produces extra wear on the engine. This is the "knocking" phenomenn, recognizable from the characteristic noise produced by the engine under acceleration.
The temperature required for radical generation depends on the structure of the fuel molecule. Branched-chanin hydrocarbons are more resistant to radical formation than straight chain hydrocarbons because the branching increases the fraction of the hydrogen atoms that are on methyl groups. The C-H bonds are stroner for methly groups than for methylene groups. Consequently, methylene groups are more susceptable to attack by thermally activated oxygen molecules, which pull off a hydrogen atom, leaving a hydrocarbon radical. Since straight chain hydrocarbons have more methylene groups than do branched chain hydrocarbons, they are subject to pre-ignition at lower temperatures.
The performance of gasoline is largely a function of its octane rating. Gasoline is a mixture of low-boiling hydrocarbons, most of them containing seven or eight carbon atoms. Among these, 2,2,4-trimethylpentane (iso-octane) is particularly resistant to pre-ignition do to its hight branched structure. It is assigned an octane rating of 100. The zero of the octane scale is set by n-heptane, a straight-chain hydrocarbon w/ a strong knocking tendency. the octane rating of any gasoline is then set by comparison w/ these two hydrocarbons in standard engine tests. "

[F22-Raptor]

Originally posted by treeh8r
Quote, "Chemistry of the Environment", pg. 179:
Knocking and Octane: Combustion is a radical chain process, similar to...that allows the oxygen to combine very rapidly w/ the fuel molecules. The spark-ignition engine of automobiles works by igniting a mixture of gasoline and air w/ a spark. The air/fuel mixture is first compressed by a piston in a cylinder, then ignited. The spark fragments the fuel molecules in its path, generating enough radicals to set off the chain reaction. The force of the explosion on the piston delivers power to the drivetrain. The greater the degree of compression, the greater the power. However, the compression stroke itself heats the fuel; at sufficiently high temperatures, the fuel molecules can fragment spontaneously, setting off the explosion prematurely. Pre-ignition lowers the power generated and produces extra wear on the engine. This is the "knocking" phenomenn, recognizable from the characteristic noise produced by the engine under acceleration.
The temperature required for radical generation depends on the structure of the fuel molecule. Branched-chanin hydrocarbons are more resistant to radical formation than straight chain hydrocarbons because the branching increases the fraction of the hydrogen atoms that are on methyl groups. The C-H bonds are stroner for methly groups than for methylene groups. Consequently, methylene groups are more susceptable to attack by thermally activated oxygen molecules, which pull off a hydrogen atom, leaving a hydrocarbon radical. Since straight chain hydrocarbons have more methylene groups than do branched chain hydrocarbons, they are subject to pre-ignition at lower temperatures.
The performance of gasoline is largely a function of its octane rating. Gasoline is a mixture of low-boiling hydrocarbons, most of them containing seven or eight carbon atoms. Among these, 2,2,4-trimethylpentane (iso-octane) is particularly resistant to pre-ignition do to its hight branched structure. It is assigned an octane rating of 100. The zero of the octane scale is set by n-heptane, a straight-chain hydrocarbon w/ a strong knocking tendency. the octane rating of any gasoline is then set by comparison w/ these two hydrocarbons in standard engine tests. "

Umm ok. Thanks for the lesson on gas???

[treeh8r]

There is still more; on BTEX and MTBE, and other additives; also lead. But I thought I'd keep my reply short.

[mkeomec]

Well, so using a lower octane gas has more knocking. I'm just wondering if this will increase engine wear and affect performance for the Celica GT. If our car was tuned to 87, as several people have already stated, than can i assume using 91 octance won't improve performance? I sure feel like i'm going faster with 91, but it could just be my imagination.

[JohnnyWash1]

Originally posted by mkeomec
Well, so using a lower octane gas has more knocking. I'm just wondering if this will increase engine wear and affect performance for the Celica GT. If our car was tuned to 87, as several people have already stated, than can i assume using 91 octance won't improve performance? I sure feel like i'm going faster with 91, but it could just be my imagination.


It is 100% your imagination. It's not your fault; marketing is built around the principle of creating a need. High octane and horsepower go hand in hand when it comes to marketing. Use what your car asks for, which is 87. If you start modifying your car, i.e. higher compression, forced induction, timing changes--then you can consider upping the octane to prevent detonation. But if you car does not detonate now, it doesn't need anything higher than what is recommended.


Jon