kylesc400

does anybody know which major oil/gas distributors use the highest octane gas? is this specific to where you live? around here i've found that exxon/mobile, amoco/bp, and citgo all use 93 octane. shell uses 94 octane. i'm going to check out texaco in like an hour and a half in hopes of finding someone that uses 96 or something. am i forgetting about some other large gas company that may have a higher octane gas?

kylesc400

i ran a search for 'octane' and reviewed some older posts and came across one that was discussing octane boosters. the one i picked up was in a black bottle from napa, labeled as 104 octane booster. says its safe for catalytic converters and oxygen sensors and safe for use in every tank. it recommends that i put it in before refilling my tank, should i wait till im damn near empty or is it fine to put it in with 1/4 tank left? will i really notice any kind of smoother acceleration or better performance?

mooretorque

No, you won't notice anything with octane booster except lighter wallet. Your SC's ECU is optimized for 93 octane; anything less, and the knock sensors will reatard timing with resultant loss of power, but unless you increase your compression ratio (new pistons) or add forced induction (turbo or supercharger), you won't get any MORE power with more octane.

Net: waste of your time and money.

kylesc400

actually i just tried it and noticed *mildly* better low end response. could this be because my car has high mileage on it and to my knowledge has never had anything like this or techron put in it before? and dont say it was the placebo effect, i performed a lil highway/city combo with/without it in, watching how my speedo/tach responded to how much pressure i was putting on the gas pedal. ran it on the same streets too. i guess i was impressed because i expected pretty much nothing but got a little bit better throttle response below 40mph.

kreativ

I still say its placebo effect.

mooretorque

kyle, most gasolines have additives such as techron, but if you did have a little carbon buildup on the valves (since you mention high mileage), you might be getting some knock on 93 octane. you'll never hear it, but you'd lose a little performance as knock sensor tells ECU to dial back your timing, compared to situation where there was zero knock. So, the good news is, you might actually have a little more grunt with the additive. The bad news is, you're only back to stock performance if that is indeed going on.

But the placebo effect is powerful; post numbers from a g-analyst or other accurate data recorder to get the real story. We are all on the edge of seats, waiting...............

kylesc400

i figured it was probably due to build up of some sort thanks to all the miles that were put on it before i picked it up, but i know i felt more linear + smoother power flow at low speeds. ill see what i can do as far as data goes. btw, has anybody ever tried the sunoco 110 octane gas from racegas.com? apparently you can get this stuff at a pump at various places around the country. wonder if that would help at all.

gebo

Mooretorque,

Are all Lexus' that require hi-octane optimized for 93 octane? I have a '98 LS4 and '00 GS3?

Great info.

Gary

mooretorque

WRONG!!!! Me, that is.

The correct Octane Rating number for our GS is 91, not 93. The RON (Research Octane Rating) number is 96, but what you see on the pump at the gas station is the Octane Rating number.

Apologies to all who read the previous posts in this thread. I am an idiot.

RhoXS

The energy content of gasoline is not determined by the Octane number. Octane only effects gasolines tendency to detonate (burn with sonic or supersonic flame velocities). The higher the octane, the less likely for detonation to take place. Detonation is very destructive so this property of gasoline is very important to control.

High compression ratios establish conditions that tend to make gasoline detonate. Engine designers like high compression ratios because high compression engines produce more power for the same weight, etc. Therefore, the compression ratio is an important factor in determining the minimum safe Octane to prevent detonation. The important point here is that compression, not octane, determines how much power is potentially available.

The allied aircraft in World War II had a large performance advantage over the opposition. A major reason for this was because the US government made a decision prior to the official start of the war to standardize on high (I think 100) octane Av gas. The engines performed better, not because the gas contained more energy, but because the engine designers were free to design higher compression engines.

In other words, the previous comments about "lighter wallets", "waste of money", and placebo effect are very true. Paying more for higher octane gas will do absolutely nothing for performance. This is easily proven on a dyno.

kreativ

RhoXS,

The Camry V6 and ES both have 10.5:1 compression ratios, yet Toyota specifies regular unleaded fuel for the Camry and premium for the ES. The ES V6 has VVT-i and 16 more HP, but if the compression ratio is the same, is there any valid reason that premium is specified? Or is premium specified just because that is what is expected of a luxury car.

hyperopt

Besides the compression ratio, timing advance also plays an important role in octane requirement. The more the timing is advanced (up to a point of course) the more power is produced and the engine also runs smoother as well. Generally, the engine produces most power when timing advanced to a point where denotation is about to occur. Thus, increasing gas octane alone won't necessarily give you more power. You must change, at the very least, the timing to take advantage of higher octane. Likewise, if your engine has a tendency to denotate, increasing octane will give you more power.

Mean Gene

My hod-rod Lexus tech tells me the same thing about the GS4; that is, the ECU is optimized for 93 octane ( pump or RON number as MT said ). Years ago ( uuh oh !! ) there was something called a MON rating ( Manufacturer's Octane Rating, I think ) which was significantly higher than the RON so Big Brother decided to standardize things by using a formula of ( MON + RON )/2 or something to that effect. That's the number currently shown on the pump. In any effect, the techs at my dealership told me to run only premium if I wanted performance but that it would be OK to run a lower octane grade if I chose to because the ECU would retard the timing to work with the lower octane gas. I did an experiment with my old Corvette & ran some quarter miles & mpg runs using several consecutive tanks of 89 octane & then upgrading to the 93 octane ( & resetting the ECU to speed up the "learning curve " ). It turned out that the obvious performance gain was there but the surprising data showed that I picked up almost 1 mpg just by upgrading the octane. This far offset the additional cost/gallon of the higher grade. I then tried the 104+ octane booster but there wasn't anymore gains to be found WITH THE STOCK ECU!! I upgraded to the HyperTech Stage 3 chip ( CalPak style ) & the 104+ did seem to help beyond the 93 octane when compared to the Stage 3 baseline results. Didn't have access to a dyno back then.
I'd just stick with the highest pump octane I could find unless Mo tells me that the new "Race" ECU will maximize things with a higher octane gas>

Mr_Mollari

I would hope that's not the case, as you can only buy 91 octane as premium in all of California. I completely agree with you, just get the highest octane available "premium" pump gas. Per tank the difference is only $1-$2.

They have 100 octane at the pumps at a few Unocal 76 stations here in Los Angeles, I put that into my Audi a few times. It's best when you're constantly driving, that stuff is not to have for stop-n-go driving with the occassional leadfoot. I definitely would notice a difference at 3k rpm and above. I'd like to see it on the dyno, though! My Audi isn't really stock either, there is some custom work on the exhaust from the headers->back with hi-flow cats, so I'm sure that helped somewhat.

Now, once I bring my GTI out to California, I am interested in getting APR's chip w/EMCS to switch into 100 octane mode every now and then...but that car has a turbo...

Lexmexico

I remember in the 80s Texaco had 104 Octane at some stations.

South of the border we have Pemex 93, and I really think it is about 91. However, the Mexicans tell me there is something you can buy that will knock the octane up to 106, but this sounds like a fairy tale.