What fuel do you run?
- Thread starter MacVay
- Start date
Mike07SE
New member
josh220 said:
I have always shared this sentiment. To me, and others do have valid arguments against it, it is worth it putting in premium. I'm already putting in $50-60 worth in, the extra $4 isn't killing me. Plus I have noticed performance improvement from the hi-test which has been proven that the Toy engines with VVT-i take advantage of. It always irks me when people buy a Mercedes, but scoff at the fact that the cars require premium. Well, go buy a Honda.
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Methodical
New member
It's important to note that higher octane fuels can actually have less energy in them per gallon due to additives. Meaning if you don't have an engine that can actually need or use premium gas, it really is a bad decision compared to regular.
Methodical
New member
josh220 said:
higher octane fuels do not burn hotter. Octane and total BTU's per gallon are completely unrelated.
Octane is one thing and one thing only, the measurement of resistance to detonation.
High octane fuels exist because high-compression engines, mostly not naturally aspirated, need it.
ethanol has an octane of 116... but power per gallon is drastically lower than gas, on the order of 2/3rds
Tolulene (common paint stripper) has a octane of 114..ish. It used to power Formula 1, and is a common fuel additive to, you guessed it, raise octane to this day.
Leaded gas existed to raise fuel octane. Lead was cheap. Unleaded gas costed more.
2004Runner
New member
1GR-FE V6 engine performance
I think this description on Wikipedia about the 1GR-FE engine (the V6 used in the 4Runner) will better explain the increase in both horsepower and torque when using 91 octane instead of 87 octane.
"The 1GR-FE is the 4.0L version. Bore is 94 mm and stroke is 95 mm. Output is 236 hp (183 kW) at 5200 rpm with 266 ft
I think this description on Wikipedia about the 1GR-FE engine (the V6 used in the 4Runner) will better explain the increase in both horsepower and torque when using 91 octane instead of 87 octane.
"The 1GR-FE is the 4.0L version. Bore is 94 mm and stroke is 95 mm. Output is 236 hp (183 kW) at 5200 rpm with 266 ft
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prodigy2k7
New member
Run whatever your manual says. Your car will run best at that octane rating. Your computer expects that certain octane. You may get worse mpg if you dont use the recommended octane rating.
abigpicture
New member
I burn 93 octane up until now....I may change to 87 as I installed and hho booster...today...
I have run extensive mpg test on my 96 4 runner...between
87 and 91...the result was that 91 always gets me better mpg...
just enough to pay for the price difference..and it runs better...
I also have done a thorough tune for better mPG...
just clocked 25.63 mostly HWY today...I wanted one last
test before I installed the HHO...so Now I will have to see
if
1) my mpg goes up? or 2) I can now run 87 with same results
hope I can use 87 and my mpg goes up too!!!!
I have run extensive mpg test on my 96 4 runner...between
87 and 91...the result was that 91 always gets me better mpg...
just enough to pay for the price difference..and it runs better...
I also have done a thorough tune for better mPG...
just clocked 25.63 mostly HWY today...I wanted one last
test before I installed the HHO...so Now I will have to see
if
1) my mpg goes up? or 2) I can now run 87 with same results
hope I can use 87 and my mpg goes up too!!!!
CJ3Flyr
Super Moderator
The energy of the premium is in fact a little bit lower than 87-octane fuel. The key to the 4Runner being flexible and able to run on 87 and still take advantage of premium is that it is a modern, computer engine.josh220 said:
Engines, in general, are just piston pumps. If the fuel ignites quickly with a high burn-rate and with lots of energy, i.e. 87-octane, the question becomes how efficiently the mechanical component of the pump can recover that energy. How much of that energy gets wasted as heat rather than efficiently used as pressure on the piston? The answer? If the fuel to air ratio is good, if the timing of the ignition is optimized then the answer is not too much is wasted. If the fuel were to burn a little bit slower and a little bit longer (93 octane) taking full advantage of the downward stroke (power stroke) of the piston, efficiency would and does improve. If the fuel burns slower and cooler but the fuel/air ratio is not optimized and the timing of the ignition is not optimized then there is no advantage to the higher-octane fuel. In the case of the 4Runner timing and fuel/air are optimized via engine management.
During high power consumption missions (towing), on older junkie vehicles, you can actually notice the engine running a touch hotter with lower octane fuel. You really need to be on the ragged edge of cooling capacity to notice this. If you have an oil temp gauge it's a bit easier to witness. The bottom line is the engine has a better mechanical efficiency in terms of recovering the heat energy from the gasoline and doing something productive with it when using higher octane.
There are many posts about fuel grades and the 4Runner. The most significant ones, IMHO, states the engines need a long time to fully optimize for fuel type, 4-5 tanks. Check this out: http://www.lcool.org/technical/prado_high_octane_fuel.html
:cheers:
EDIT: Let's go one step further, why not 115 octane gas if higher is better? At some point the burn becomes too slow for the amount of time available to be advantageous. In fact someone always has a story about airplane or race gas causing burnt exhaust valves. When the octane gets really high the ignition and valve timing need to be futher optimized to prevent damage from occuring. Ignition as early as 40-45BTDC (before top dead center) is not unheard of when using very high performance setups with high octane fuel...
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teampwr2
New member
2005 v-6 4Runner 4x4 91 all the way
If Im not mistaken the higher the octane rating the slower combustion rate .....The reason aviation gas is high octane due to higher altitudes and less oxygen need a slower burning fuel so the air to fuel ratio is more even .. i may be wrong but I think thats correct.
If Im not mistaken the higher the octane rating the slower combustion rate .....The reason aviation gas is high octane due to higher altitudes and less oxygen need a slower burning fuel so the air to fuel ratio is more even .. i may be wrong but I think thats correct.
Methodical
New member
Octane is totally unrelated to deflagration rate (the speed of burning). Different mixes of gas such as avgas might have a different rate of deflagration, but it is controlled in a method outside of the chemicals that relate to octane.
Meaning, higher octane fuels might burn faster or slower. The octane doesn't matter.
People think octane relates to the grade of gas. OCTANE MEANS NOTHING unless it is too low.
Think of it like this. Deflagration is the burning of gas in the manner people usually think of, as a flame front, subsonic speeds. Detonation is when burning happens so fast, it becomes supersonic. Detonation creates a shock wave (sonic boom).
Optimally, an engine want to run as fast a burn as possible, without risking detonation or any of it's effects. Faster means quicker power application, and no, the charge does not cool down in the cylinder to the point that it is not pushing on the piston.
optimally, you want your fuel to burn quick so that as soon as the piston is going down, there is 100% force pushing it down. A slow burn results in lower pressure at that point, as the fuel is still burning while the piston is going down. thats normal, but it's not preferred.
anyway, to repeat a previous post, the additional power from 91 octane only come into play at full throttle, as autoignition (detonation) is only a problem at higher heat and cylinder pressure, and until your foot is flat on the floor, the throttle never lets a cylinder get a full dose of air, and thus even with high compressing engines such as the 1gr-fe, never needs the added headroom that 91 octane fuel provides.
Meaning, higher octane fuels might burn faster or slower. The octane doesn't matter.
People think octane relates to the grade of gas. OCTANE MEANS NOTHING unless it is too low.
Think of it like this. Deflagration is the burning of gas in the manner people usually think of, as a flame front, subsonic speeds. Detonation is when burning happens so fast, it becomes supersonic. Detonation creates a shock wave (sonic boom).
Optimally, an engine want to run as fast a burn as possible, without risking detonation or any of it's effects. Faster means quicker power application, and no, the charge does not cool down in the cylinder to the point that it is not pushing on the piston.
optimally, you want your fuel to burn quick so that as soon as the piston is going down, there is 100% force pushing it down. A slow burn results in lower pressure at that point, as the fuel is still burning while the piston is going down. thats normal, but it's not preferred.
anyway, to repeat a previous post, the additional power from 91 octane only come into play at full throttle, as autoignition (detonation) is only a problem at higher heat and cylinder pressure, and until your foot is flat on the floor, the throttle never lets a cylinder get a full dose of air, and thus even with high compressing engines such as the 1gr-fe, never needs the added headroom that 91 octane fuel provides.
davefisher
New member
03 V8. I previously ran 89, but am now running 87 with no noticeable difference except in my pocket at the pump 
