Gas Octane

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BIG change on the way!!!!!!!!!!!!!!Great speaker--ALL LIES- he only fools the idiots that cannot think for themselves

 

I know guys have explained this before - and I am not trying to make myself out as some expert - but I do know more than the average person about this. I have a degree in mechanical engineering. One of the required courses I had to take was a class called Energy Conversion. The professor who taught this class were I went to school wrote the book - he is an expert on this. Higher octane - does not equate to "the good/nicer stuff". It simply has a higher ignition temperature not a higher energy content. It is intended to be run in higher compression engines to prevent premature detonation - commonly known as "knocking". If your engine isn't knocking you are wasting your money on higher cost gas. If your Tacoma's engine is knocking with 87 octane fuel - something is wrong with your engine. Period - the end. Listen if you want to save some $ - but do what you want.

 

Forgot to mention a few more things. It is actually possible for higher octane gasoline to have a lower energy content than gasolines with a lower octane rating. Contrary to what most people think, octane is not added to gasoline to give it a particular octane rating. Pure octane, which has a rating of 100 in the test engines used to test the fuels, is simply what the hydrocarbon mixtures that are sold at most gas stations are compared to. Simply put, a gasoline with a 92 octane rating has the same anti-knock/anti-detonation characteristics as a mixture of 92% iso-octane and 8% heptane. This does not mean the gasoline contains just iso-octane and heptane in these proportions - it does not. In fact, the octane rating can be raised by blending in ethanol (and other hydrocarbons as well) - and when ethanol is used for this purpose (and it frequently is) the energy content of the gasoline is LOWERED. So you won't get any more power, or any better gas mileage - you might get less! The lower octane regular and mid-grade fuels contain the same additives and detergents that are needed to keep electronic fuel injection systems clean. Running anything higher than 87 octane in a Tacoma is a waste of money - and it is not better for the engine.

 

So even if you get greater gas mileage with higher octane fuel, which equates to less $$ per fill-up (in some cases), you are wasting money?? Do the math and decide for yourself.

 

Yeah, I don't understand math.

 

X2

Seems like this thread brings out the self-proclaimed Chemists of TW.

 

Never said you did not understand math...

 

ppl seem to forget that pre-2008 tacoma manuals had the mention "use 91 for better performance". So the engine was/is tuned for using more advanced timing, which means you will get better fuel economy.

Though I don't know if the new tacomas still benifit from 91, since in my manual they don't mention it.

 

Seriously though - if you guys want to use it - then use it. I got no chip on my shoulder. If the oil companies can get people to pay for it - well hell that's free enterprise. I'd question how people are determining they get better gas mileage with premium vs. regular. You can't run one tank of regular and one tank of premium and decide on that basis. Most of the people who claim better mileage with premuim also admit that the difference is so slight that the extra cost is not really worth it. Then they try to further justify it by saying the premium is better for their engine (not), or they get more power (nope). I would say that the difference they calculated is within the upper and lower tolerance of their calculation method. All kinds of stuff affect gas mileage - not just the fuel used. Driving habits, where you drive, weather, temperature, tire pressure, etc... - and kind of fuel also. It's just funny that when someone calculates a 0.5 to 1 mpg difference - its the fuel - not any of the other things I listed. Wake up - the math you are doing is bogus - like trying to measure a gnats ass with a yardstick. It all adds up - but it ain't correct.

 

gdawg25 - I was being facetious about the "I don't understand math" thing. I know you didn't say that - and in no way felt like you were attacking me. I'm just trying to explain what I know to be true.

supralight - sorry, but no. Pre-2008 Tacoma manuals do not specify 91 octane for better performance. They specify 87 octane fuel (or 91 Reseach Octane fuel) which is the same thing. Too make things even more confusing not all parts of the world measure or specify octane rating the same. Places like Australia and Europe show the research octane rating on the pump. In the US and Canada the anti-knock index, which is the average of the Research octane rating and the Motor octane rating, is listed on the pump. Most pumps in the US show (R+M)/2 near the octane number to show that it is the anti knock index rating. The stuff about the engine being tuned or having advanced timing for higher octane fuels is incorrect. The only thing the engine would have if it needed, or would perform better on higher octane fuel, would be a higher compression ratio. Which it does not - and did not.

 

Higher elevation means you ran run lower octane rating just read it in my automotive book!

 

Yeah - higher elevation = lower pressure. Means lower compression in engine so lower octane fuel will work best.

 

I like school Really though and this is the first semester I have also, finally getting into my core classes!

 

My '09 manual say to use no less than 87 but 91 was used in testing. (Something like that)

 

If you go to Fuelly from my signature you can see every fuel up, octane, station for the 50K miles I have on my truck. The summer of 2009 was my testing phase. I drive almost the same route every day 5 days a week but this year I started driving a little differently. You can see that the biggest jump in MPG was once I install my ScanGuage and could actually see real time how different things effect MPG.

I have stopped driving my truck for my daily trip now since I purchased a used Insight. Now learning how to drive it, I have increased almost 10 MPG from when I first bought it.

 

^ I get your mileage out of my truck with lift and 33's so I guess I should never complain about my mileage!

 

They wont listen to reason. Scientific method is foreign to them. They thrive on invalid arguments and fallacious observation. Youll find its no sense typing anything on any forum if you want reason.

 

I didn't multi-quote your original posts (too lazy). You are correct in your post and theory, but you did not go far enough. Higher octane will not increase performance and milage IF your engine control system has no ability to change the timing.

An engine that has knock sensors and the ability to dynamically add/subtract timing as the fuel dictates can gain increased power/performance by running higher octane fuel The engine controller is able to add more timing than if a lower octane fuel is used.

The increased power may show up as increased milage, or as "smoother" running. I believe if you search that there is a thread or two where 87 and 91/93 were dyno'd and did show a gain.

Now, personally, I have run several months of 87 and several months of 91 in my 09 since it was new. I have seen no noticable changes in how it runs or in milage, so I use 87.

 

Stormyday - your 09 manual does say to use 87 octane fuel, or higher. In parenthesis (after the 87 octane) is also says (91 Research Octane). 87 octane is equivalent to 91 Research Octane. Research octane doesn't mean they tested the Tacoma's engine with 91 octane fuel. Research octane is a different method of measuring and reporting octane levels - it is used primarily in Australia and Europe. 91 Research Octane = 81 AKI octane (AKI = anti-knock index, which is the same as the (R+M)/2 method. There has never been anything in the Tacoma manuals that told anyone to use higher than 87 octane for better performance or gas mileage. It just says to use 87, or higher, to prevent engine knocking.

 

Just to, I was bored in the parking lot while girlfriend was getting some groceries for dinner. Got out my 2006 owners manual and looked up fluids, and it states that in the 1gr-fe v6, 87 octane or higher (RON 91) should be used....however for better preformance use premium 91 octane (RON 96).
I always have used 91 octane from shell and have always got 21-24(AVG. 22-23)MPG. NOt that this makes any difference, and I am probably wasting money but to each the own.