Gas Grades

[Orange Peel]

Originally Posted by jasbus

Higher octane cannot and will not increase performance, nor will it give you better gas mileage. Simple, and true.

Yes, it is simple and true,but some people won't let the facts get in thier way.The octane number on the pump is nothing more than a measure of the fuels anti-knock rating.Its also a myth that higher octane slows down the flame speed,and thats simply not true.The chemistry make up of the fuel is what determines flame burn speed, not octane. Now if you want to get into in-house blended racing fuels,and modified high compression vehicles,thats a whole nother ball game.

If your car isn't suffering from detonation (AKA pinging/knocking) then you're not getting any benefit.

[sprj8008]

Originally Posted by Orange Peel

Yes, it is simple and true,but some people won't let the facts get in thier way.The octane number on the pump is nothing more than a measure of the fuels anti-knock rating.Its also a myth that higher octane slows down the flame speed,and thats simply not true.The chemistry make up of the fuel is what determines flame burn speed, not octane. Now if you want to get into in-house blended racing fuels,and modified high compression vehicles,thats a whole nother ball game.

If your car isn't suffering from detonation (AKA pinging/knocking) then you're not getting any benefit.

So the fact that I get better mileage is not a benefit? The fact that my oil is visibly cleaner is not a benefit? The fact that my tailpipe is clean is not a benefit?

Maybe I'm on glue. And thanks everyone for the discussion, it's always fun. Reminds me of the water cooler.

[Orange Peel]

Originally Posted by sprj8008

So the fact that I get better mileage is not a benefit? The fact that my oil is visibly cleaner is not a benefit? The fact that my tailpipe is clean is not a benefit?

Maybe I'm on glue. And thanks everyone for the discussion, it's always fun. Reminds me of the water cooler.

It isn't from the higher octane,now it could be from running a better blend of gas that has a better chemical makeup of components. Again,the octane number is a anti knock measurement the gas companys use, and it used to be called "the anti-knock index,"

Maybe we have a Tribologist,or a chemical gas scientist that can enlighten us?

I have a clean tailpipe,the oil can barely be seen on the stick,and my fuel mileage isn't any better running a higher anti-knock index.

EDIT: I just noticed you have a supercharger,now that will require more octane,and you probably will see a performance difference with a lower octane.

[duke boy]

Since there is such a discrepancy here, someone who knows the workings of the Tundra's engine management computer needs to answer the question. There are plenty of people on here who swear that it makes a difference and plenty who are positive that it doesn't. I know for a fact that in my Z28, there is a difference. This is because it's engine management computer can advance the timing when higher octane fuel is used. As everyone has covered already, higher octane gas reduces detonation but another way to reduce it is to retard the timing. The engine management computer determines the correct timing and can sense detonation and retard the timing in response, but is the maximum degree of timing that the engine management computer can achieve satisfied by 87 octane gasoline? If higher octane gas is used and the timing is advanced, performance and efficiency will increase. Most people posting here probably know all of that, so what we need to solve this dispute once and for all is someone with inside knowledge of the engineering of the engine management computer. Does anyone know for sure if the Tundra's engine management computer will advance the timing that far? If so, how far, enough for 89 octane? 91? higher? I doubt there would be any benefit using anything higher than 91. Maybe not even higher than 87. Also, the 05-06 is different from the previous years, so maybe it will make a difference on the new trucks and not on the old.

[sprj8008]

So now I have a question. What is "premium" to you guys? The best octane I can get is 91 or 92 (depending on brand).

I'm under the impression the VVTI engine requires 91. It's a 9.6:1 compression as I recall so there is a difference from my 9:1.

This sounds like a question that gadget my have resources to respond to. I recall he had some specs on the computer's ability to manage injector cycles while trying to run/control larger injectors. The parameters for timing controls are not too far from the injector cycle controls.

Jason

[jasbus]

Originally Posted by 05Tundra

Here is a quote from my 05 Tundra manual: "1GR-FE engine (v6), select octane rating 87 or higher. For improved vehicle performance, the use of premium unleaded gas with an octane rating of 91 or higher is recommended"

"For 2UZ-FE (v8) engine, select octane rating 87 or higher".

there it is fellas, straight from the manual.

You may need to read it closer... like between the lines.
Our gas is rated R+M/2 or the average of RON and MON. My manual states :use research octane 91 or above. Which, in the united states by our fuel standards is 87. My manual doesn't even state the R+M/2 standard. Maybe my manual was printed for use in Guatemala or something...

[slimb]

If you are looking for more response from fuel, find a small airport that deals with a large # of recip. planes and ask if they will sell you some 100 low lead. This is what a lot of people do with "hot rods".

[Orange Peel]

Originally Posted by jasbus

You may need to read it closer... like between the lines.
Our gas is rated R+M/2 or the average of RON and MON. My manual states :use research octane 91 or above. Which, in the united states by our fuel standards is 87. My manual doesn't even state the R+M/2 standard. Maybe my manual was printed for use in Guatemala or something...

The 91 sounds like US standards.Usually Europe (and others) run off RON,which will usually be in the 95+ range.The 95 RON is the same as our 91 ron/mon/2 standard.

Im guessing the higher octane Toyota requires (atleast on the Tacoma) has something to do with the VVT-i.Maybe the timing is advanced enough at higher RPM's that a higher octane will be of benefit.I know my wifes 4-runner will ping at higher rpm's with 87 octane.

When I said in one of my other post that a higher octane is of no benefit,I only mean its of no benefit if your not having detonation.Lots of people think higher octane numbers makes more of an "explosion," which isn't the case.I didn't mean to sound like (although I did) certain variables like super chargers,advanced timing,and high compression engines don't benefit from higher octane.I admit I kinda jumped the gun and ASSumed that sprj8008 was hinting at the "more explosion" theory,and that was wrong on my part.

Here's a snippet from the Chevron website about higher octane:

"Traditionally, premium has had a slightly higher heating value than regular, and, thus, provided slightly better fuel economy. The difference — less than 1 percent better — is not large enough to offset premium's higher cost. The difference is likely to be less or nonexistent between grades of reformulated gasoline.

There can be differences in heating value between batches of gasoline from the same refinery or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify the gasoline with a higher heating value." END

and another snippet from Chevron:

"Don't Buy a Higher-octane Gasoline to Improve Fuel Economy

Octane and energy content are not related. Premium-grade gasoline doesn't necessarily have a higher energy content, especially if it is oxygenated.

The exception to the above advice is when a lower-octane gasoline doesn't satisfy the octane requirement of the vehicle's engine. The abnormal combustion that announces itself as knocking reduces engine efficiency. Using a higher-octane gasoline that eliminates knocking will improve both engine performance and fuel economy.

Many newer vehicles with an electronic control module (ECM) also have a knock-sensor device. When the sensor detects knocking, the ECM retards the engine's ignition timing to eliminate the knocking. This happens so quickly that the driver never hears the knocking. But retarding timing decreases power and fuel economy. A higher-octane gasoline may improve the performance of knock sensor-equipped vehicles that have less power than when new." END



Good thread,and I hope to learn more about the VVT-i effect on octane.

[MEvang]

My manual (2001) says nothing about using 91 octane for improved performance. This may have changed as the engine HP increased.
Mine reads:
Fuel type:
Unleaded gasoline, Octane Rating 87
(Research Octane Number 91) or higher
I read this as a MON- RON sensitivity rating 87- 91 octane.
In other world Toyota feels the engines will operate safely on 87 octane, but under harsh conditions ( foot to the floor driving or heavy hauling or towing) you would be better off with higher octane fuels.
True, the engine management system will compensate and keep you from engine damage under harsh conditions with the lower octane fuel (with less performance).
True, the only way to tell what the computer sees is by connecting a scanner and watching the knock sensor parameters as you drive. Only problem here is these parameters will likely change under different driving condition and not only the octane but different fuel blends.
Problem here in the US fuel blends can change greatly from one state to another.
This is one reason it takes a computer to get thing to run right now days.

So if your driving unloaded trying to sip gas as many of us are right now, 87 will be fine. But when you hook up to the boat or camper and want to put it to work, you will be better off to top off with a higher octane.
Mike

PS Sorry Slimb you can't put any type of leaded (aviation) fuel in these vehicles. It will clog up the O2 sensors and destroy the catalytic converters. Don't even try a little!

[05Tundra]

Well, since we all are driving Tundra's, we shouldn't have a financial problem filling up the tank with either 87 unleaded or 93 premium. If you are curious, you should completely fill up your tank (where it is visible in the neck) with 87 unleaded and put some highway miles on it, and check your mileage. Then do the same thing again with 92 or 93 unleaded and check your mileage. You will then know for yourself if premium gas makes your vehicle run better/gives you better mileage or if it makes absolutely no change. I would not recommend doing this to check city mileage. IMO, there are too many variations (stop/go traffic, hard braking, rapid accelleration, etc). I for one, prefer using plus or premium fuel. It could be a mental thing, but in my 05 DC 4wd Tundra, in my state...........premium fuel equals better performance and adds a few more miles to my tank.