Does 89 octane save, and is 93 octane even better?

higher octanes don't do anything but prevent preignition, which won't do much in an engine designed for using 89, ECU just compensates for whatever gas you're using

our engines don't need 91
 
literally burning money :eek:

My theory is that people's stone feet turn into feathers and eggshells when they fill up with 91 because of how much they paid for that tank of gas; and suddenly they see better MPGs
 
whippersnapper02 said:
I believe Gadget made dyno runs with 93 octane and saw no changes in power over 87 octane. Run what you like though
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That's actually helpful. I was getting disappointed by some of the personal opinion one-liners.

A little about me: I'm a chemist. I like technical stuff.

There could be other variables that weren't included in the dyno run. I drive in mountainous Pennsylvania, up and down steep hills. I couldn't drive gentle (as one person speculated) if I wanted to.

Also the altitude is high.

And it's been extremely cold.

I like to see any equipment operated at its optimum. To joke around -- to make a point -- (sarcasm) if 87 saves money, then why not run 80 octane and save even more money? I mean, if octane doesn't make a difference. Right? (/sarcasm)

When gas octane is below optimum then the engine's knock sensor will detect this. Then the computer retards timing to compensate. I read that can be as much as 10 degrees. It can result in flamed valves, and lower mpg.

Obviously, when knock sensors say that the gas is below optimum, and the computer decides what to do, and all this assumes that the sensor and the computer program work great, then timing is retarded. If all this has to be done, then it can't be optimal -- if 87 is not the optimal octane. Maybe it is. Don't know.

All I can say is this. I wanted to save money and went to 87. I wanted it to work. But, I noticed an immediate decrease in mileage and the responsiveness in power just seemed to be sloppy I moved down from 89 to 87 octane -- under my conditions. Then back the other way when I moved back from 87 to 89 octane.

Maybe it's because the computer took a while to readjust.

Maybe it's a lot of things. But if I'm going to take the time to share all of this, then it would help me stay interested if I got back something more than 1 liner opinions.

All I need to justify moving from 87 to 89, if my math is correct, is a 1/2 mpg. That's not much when there are so many variables.
 
Octane below the minimum requirements would cause the engine to run improperly. Minimum for this engine is 87 not 91. Yes the ECU will adjust timing accordingly to the knock detected by the knock sensors but it won't magically improve upon its setting from the factory even if you put the highest octane fuel you can find. Again, run what you like. In the end the cost difference is negligible unless you are burning through a lot of fuel and if you are trying to save fuel you have the wrong vehicle.
 
Oh, one more thing, chemically speaking, just from a perspective of chemistry. Let's try it this way ...

Point #1: If 89 octane doesn't trigger the sensor to retard timing while I'm driving up a mountain in Pennsylvania -- then the fuel / air will be compressed more before ignition, because the timing wasn't retarded.

True? Any arguments on point #1?

Point #2: If the fuel / air is more compressed before ignition, then it will yield more performance or more mpg.

True? Any arguments on point #2?
 
I'll say 87 is optimal for stock tuning. The manufacturer wouldn't tune the engine on 87 only for to knock most or all the time to the point where you would need higher octane. Well it is Toyota so you never know.
 
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Our engines won't optimize the higher octanes

and this is more of a mechanical discussion rather than a chem one. lol
 
whippersnapper02 said:
I'll say 87 is optimal for stock tuning. The manufacturer wouldn't tune the engine on 87 only for to knock most or all the time to the point where you would need higher octane. Well it is Toyota so you never know.
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That is a great answer. It actually does make good sense. Yes, it would be logical to tune an engine for 87.

I guess my only wonder is under what conditions. They might have tuned based on driving on flat land in Ohio, rather than up mountains in Pennsylvania.

Just an update: I'm half way through my first tank of 93 octane. It appears that I might not be getting better mileage with it? A little early to tell yet. I have to fill it up to see.
 
Konaborne said:
and this is more of a mechanical discussion rather than a chem one. lol
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If I was discussing whether removing an air filter can increase mileage, or at what pressure a compressed air tank will explode, then I'd have to agree with you.

On the other hand, how well gasoline explodes is profoundly a subject of chemistry. You'll just have to trust me on this.
 
Tacoma-Robert said:
If I was discussing whether removing an air filter can increase mileage, or at what pressure a compressed air tank will explode, then I'd have to agree with you.

On the other hand, how well gasoline explodes is profoundly a subject of chemistry. You'll just have to trust me on this.
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I'm a 3rd year university chemistry student. Doesn't mean ****, but if we were mainly talking chem I might have more to contribute. haha

we're mainly talking about the engine rather than the combustion/compression of hydrocarbons
 
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Tacoma-Robert said:
I guess my only wonder is under what conditions. They might have tuned based on driving on flat land in Ohio, rather than up mountains in Pennsylvania.
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ECUs have a barometric sensor built into them. The reason you lose power in higher elevations is because the air is less dense. Tuning each individual truck for each individual owner would maximize power output and MPGs but that's pretty much impossible with mass produced vehicles.
 
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whippersnapper02 said:
Tuning each individual truck for each individual owner would maximize power output and MPGs but that's pretty much impossible with mass produced vehicles.
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My guess is that it's simple: Tacomas are tuned for the conditions used to produce that MPG rating that's printed on the window sticker when the vehicle is sold. I'm thinking that most everyone's conditions could be different in some way or another. For me, I'm both at normal altitude and at high altitude often during the same day. I'm always driving up and down mountains so much that it sometimes makes my ears pop, even on the major highways. My mileage is usually about half in town and half highway. I have a 4cyl engine.
 
Well, it's done. I'm now buying 93 octane for my 4cyl tacoma until I prove myself wrong. But that may not ever happen cause I can't stand running 87 octane any more. After watching my mileage and my driving, I have concluded that 93 octane has a HUGE difference in power and mpg over 87 octane. It's better both in performance and in economy. I can tell in the rpms that are required to maintain speed when climb the same hill. I can tell because it doesn't shudder when I'm slowing to a stop. I don't have to push my foot through the floor to maintain speed on a steep hill. I don't think that I was biased on how it feels, because I wanted 87 to be best before considering cost per mile, and at one point I even believed that 93 wasn't going to make a big improvement in mileage. My mileage, under my conditions which are discussed at length elsewhere in this thread, increased from 17 mpg to 21 mpg*. I'm now getting 400 miles on a tank of gas driving half highway and half city -- almost all of it up and down steep hills. And it's a far better ride - not splitting hairs it's noticeably better when driving up medium to steep hills. There is also theoretical justification which I covered in previous posts in this thread. By the way, I use Exxon. It's has credibility: http://www.toptiergas.com/retailers.html *Disclaimer: My study was a small about 5 tanks of gas. But there is so much other evidence that goes along with it that this is at least a very strong theory that's worth additional testing for detail oriented people. At the very least, the darn thing just drives SO much better up a hill! So, anyway. There it is. Just sharing. Again, this is still a theory, but now I feel it's a really strong one. Use this info or don't. Check it out or don't. As someone here said to me, "drive what you want".
 
Thewarriordinghy said:
Heres a question that might be dumb.... Whats the best to punch it on the freeway (interstate) home?
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GREAT QUESTION! Seems to me that higher octane has provided me with more power in my 4cyl 2013. Power's what you would want, true. There is also theoretical justification. See my post #27 in this thread. http://www.tacomaforum.com/showpost.php?p=19652&postcount=27 The disclaimer would be conditions. I don't know if it would be a hugh difference on flat land. Maybe within certain parameters it might not matter? Try it both ways. Let us know what you find!
 
Butt dynos are not an accurate tool to measure power increases.

On a side note, my friends twin turbo automatic GTO with 530hp to the tires got 24mpg from California to Vegas. That's with some full throttle runs along the way. Haha.
 
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