Gas Octane

Unless you are running higher compression or some sort of forced induction (turbo/supercharger), you really dont need to increase the octane from the lower amount.

The lower octane amount in a given location is generally based upon the minimum requirement for that altitude. Altitude in areas close to sea level the lower octane # is generally 87, whereas higher elevation locations the lower # octane is 85.

If you experience pinging or knocking then certainly go up by one octane level, (however I would suspect an issue if you are experiencing knocking or pinging.) Most modern engine computer systems are designed to automatically adjust timing advance to accommodate whatever octane gas you are running. The amount of power gains are minimal in a normally aspirated (NA) vehicle when you run the higher octane gas. in a sense you are throwing your $$ away by putting premium in your tank on a NA vehicle.

FWIW

 

EVERYTHING else being EQUAL higher octane will not gain you more horsepower.

To-days engines are not equal though, with knock control, variable valve timing, electronic ignition timing, etc. it is POSSIBLE higher octanes fuel CAN yield a slight increase in power. It would take a while for the ECU to relearn this however, which will be different on every car and even between similar cars.

There's scores of people that will argue this, but it is a simple fact. And before it comes up, high compression and boosted applications are specifically designed for the higher octane requirement, so they are not EQUAL to the "average" engine.

Besides a higher OCTANE fuel is actually LESS explosive than the regular grade, it takes a little more to get it to ignite, thus is the whole reason it is used in higher compression/boosted applications to avoid KNOCK not give you more power.

Octane and Octane Boost Additive threads are always entertaining and on the other forums I visit, which involve a lot of boosted vehicles, these threads are usually immediately closed (they have a sticky that links to everything you could ever possibly want to educate yourself about Octane).

 

I use 85, but I live at over 5800 feet.

 

i usually run my truck on 87. recently i drove across the state of WA, and experimented by topping off with 92 octane, to average my tank of gas out to about 89-90 for my drive heading east. on the drive back west, i think i filled with 92 again. for me, it made a bit of a difference. on a long drive like that where RPMs are kept up a little higher, the higher octane does seem to make a difference. for average daily driving, she gets the 87.

 

I agree and find this to be true with most of the vehicles I've owned. Only run 91 in my Taco since it left the lot, so can't say how it does on 87.

87 in my Geo Prizm = 28-31mpg
91 in the Geo Prizm = 37-41mpg and it would do a mean burnout (even at 235k)

My girlfriends 08 3.7L Jeep Commander was getting 14mpg on 85 till I caught her using 85! With 91 she's up to almost 20mpg

 

^^ Concur!! ^^

 

I bet if someone filled your tank with 87 without your knowledge you'd never notice it. Besides wondering how your tank was suddenly full.

No way that a little octane difference equals +10mpg with a prizm or +6 mpg with the Jeep.

 

Me too.

 

commtrd is correct. If all things are the same (no electronic variable ignition or variable valve timing) 91 will not help your engine other than possibly running a little cooler.
THERE IS LESS ENERGY IN HIGHER OCTANE FUEL. People don't realize that the higher the octane of the fuel, the more anti knock additives are added, reducing the actual percentage of petroleum, and the amount of burnable fuel. The plus side of high octane fuels is engines that can compensate for different octane fuels (VVT and Variable electronic ignition) can change the timing to increase compression and have a more efficient burn/ produce more power.
I believe second gen Tacomas have VVT, which plays a huge part in changing the timing and making the most out if whatever octane fuel you run.
Burn whatever you want, in newer engines with VVT there will be an increase in power and efficiency if you run premium. That is a fact, but don't be hating on good o'l 87! Alot of people dump money down the drain because they just don't understand the difference!

 

Octane will not, itself, increase power. This is true.

It's not true that high octane fuel has less energy. Octane as a property of fuel is independent of energy content. This is a myth that got started because ethanol is one way to increase a fuel's octane rating, and ethanol does, indeed, have less energy content than gasoline.

It's also true that engine computers can control timing and fuel mixture with regard to throttle position. They do not control compression. Compression is a function of engine design. It is what it is. It is true, though, that higher compression inherently increases the risk of detonation.

It is impossible to generalize about whether higher octane gas will affect performance. Objective tests (the Car and Driver piece is often cited) show that some cars do better, some the same, and a few worse. Every engine is different. In the case of the 1GR-FE, Toyota's own numbers say that torque is increased by 13 lb/ft on premium (they don't talk about this in their literature because of SAE reporting standards). In fact, their marketing takes advantage of this to differentiate Lexus-version engines by using the premium fuel power rating rather than the regular fuel one (a bit sneaky. They get around the SAE reporting standard by recommending the use of premium fuel). Horsepower for this engine is barely affected by octane in the V6. So what good is 13 lb/ft of torque? If you're towing or you're at altitude, it's kind of silly to run regular when the extra grunt is there for the taking. In normal driving, you probably wouldn't notice the difference, especially since the added torque comes at higher revs... so it won't help you win drag races

There really are facts out there on this stuff. They're just hard to find because myth and speculation have filled the information void manufacturers have left. The SAE standard says that you have to report power output using the 'recommended fuel'. For most cars and trucks, it would be marketing suicide to recommend premium fuel, even if it makes a difference, which it doesn't always. Thus, multi-page threads arguing about how many angels can dance on the head of a pin.

The fact is that your V6 Tacoma will make more power on premium. Whether it's worth it or not is a matter of personal choice. Otherwise, this particular engine will probably go forever on regular with no ill effects.

 

True and untrue.

Static compression ratio is a function of the design of the engine.
Dynamic compression ratio is what really counts because it takes into account the flow, latency of gases, back pressures, valve overlap, etc..., can easily increase or decrease with VVT.

You could even argue that changing the ignition timing can affect this as well, but that is actually a different argument and effect but is often confused.

 

I've always used 91 octane since new. Today I pumped regular unleaded.

 

91 for me, before & after supercharger, Shell as well. My little brother's '73 240Z, '89 240SX, '88 Supercharged MR2 & '96 540 all seem to like Shell, so I took his word for it.

 

how about this for the next argument:

All gas is the same. I have heard this one a lot. I can understand that all gas is the same. it is the additives that each major brand add to the gas that make it worth using or not. for Circle K, Arco, and the other stations that tend to run really cheap, I have always had a worse time with the gas from there, so i quit using them.

 

I'll have what you're smoking.......................................

 

Think what you will, I only run full tanks every fillup, divide the trip by the gallons, get the REAL MPG (not what the display says) and repeat. The numbers don't lie.

 

^^^^^

It is well understood that E0 is better than E10, you would likely see the same results with E0 87. I used to get E0 85 and I saw a 6% increase over E10. Try some E10 91 and your benefit is gone.

With a scangauge it is easy to confirm the difference between 2 fuels. With E0 my fuel adjustment factor is only 2%. With E10 it is 8-9%.

 

http://en.wikipedia.org/wiki/Energy_density

Storage type Specific energy (MJ/kg) Energy density (MJ/L)
Diesel fuel/residential heating oil 46.2 37.3
Gasoline (petrol) 46.4 34.2
Gasohol E10 (10% ethanol 90% gasoline by volume) 43.54 33.18
Ethanol 30 24

Diesel also gets some efficiencies from the higher compression ration & lack of throttle making the recoverable energy even higher than gasoline.

I have seen no significant change in my mileage going from 87 to 85 (Colorado altitude). I'm relying on averages and a large sample size on a monotonous commute (no cruise control). Even with cruise control you need a larger sample size to overcome bias due to such things a incline, wind, tire inflation, etc. The variation on my commute is astounding. Over 364 gallons and about 100 days the graphs of my mileage on the same exact commute I often vary upwards 1-2mpg. My best was 23.27mpg (happened to be on 87), and worst was 19.5mpg (happened on 85). Average is 21.07 across 85 & 87, usually ranges from 20.5 to 21.5mpg.

I use FuelLog (for Android) to track my mileage. The author is claiming his next version will have options to track the octane you fill up with and dissect stats based on that.

2009 TRD Sport access cab - Stock

 

i always use 91... Toyota uses 91 in all Lexus vehicals, so if its good enough for lexus its good enough for me and will be just fine, also i gain alittle power as well

http://en.wikipedia.org/wiki/Toyota_GR_engine#1GR-FE <--- check this out just for kicks