Gas Octane

This is a very good article on octane.
http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/question90.htm

 

I just read this article again. It used to be longer and went on to explain how some vehicles with VVT plus computer can increase the compression ratio with high octane "rated" gas. Sometimes the result of higher compression ratio is more horses and/or higher fuel economy.

Some people are confused and believe when you buy higher octane and pay more money you get more energy.

 

Reposted, to once again dispel this popular myth:

Energy density in terms of volume (i.e., how we purchase it):
Gasoline = 34.2 MJ/L
E10 = 33.7 MJ/L
100% Ethanol = 24MJ/L

The difference in energy content between gasoline and E10 (gasoline blended with 10% anhydrous ethanol) is less than 1.5%. That negligible difference won't be seen above the noise of all the other variables affecting mileage and performance.

 

It varies from state to state. California is about 5-6%.

 

Let's just say that ethanol is a very political issue, and it's very hard to get accurate information about its value, its carbon implications and the effects it has on engine durability and performance. So I'm sure you mean this well, and I'm sure you believe in your source, but I just have to shrug and go with experience. My experience is simply that an engine designed to run on gasoline runs better on gasoline (yours may vary, but that's mine). I've had cars where the difference was so pronounced that running E10 produced a sooty tailpipe regardless of octane rating, evidence that the car - for whatever reason - was running rich on this fuel type. Some cars tolerate it, some don't. My Taco is getting 24 miles to the imperial gallon consistently, the sign of a happy motor. I'm sticking to my no-ethanol policy.

 

I have no dispute with your personal observations or politics.

Little effort is needed to find accurate information on the energy content of a variety of fuels. Your statement regarding the energy content of gasoline vs. gasoline/ethanol blends was wrong, and I pointed that out.

I can certainly believe that you observed a sooty tailpipe after running E10. Besides producing fewer combustion products, E10 can also act as a solvent that removes deposits left by gasoline combustion. So it's more likely that what you were seeing was the effect of E10 removing crap left by burning gasoline, not an indication of a richer burn.

 

In fact, no. I'm not going to bother explaining the diagnostic process we went through, but it was not the effect of a 'solvent' acting on combustion biproducts. It was the effect of an ECU retarding timing and enriching mixture. (I'm not saying this would occur with every engine, I should stress).

The internet, believe it or not, contains the odd bit of false information, sometimes spread by people with an axe to grind. On those occasions, first degree observations are more reliable.

 

Then perhaps you can put down your axe and present those diagnostic procedures and their outcomes to support your supposedly more reliable contention. Yes, E10 tends to 'enlean' the air/fuel ratio, resulting in a more complete burn and fewer combustion products.

But getting back to the original issue: Can you post some real data that dispute what I posted about the relative energy content of gasoline vs. E10? How about some real data that dispute E10's solvent characteristics?

 

Are you new on the internet? Come on... you're going to use the "post up your data" line with me? And then I'm going to be so stupid as to believe that I can change your mind? Sorry, no. We both know that we can spend all day firing links at each other and, from the safety of our desks, refuting each other's sources. It's a silly game.

My experience was trackside with one car, and was not presented as a generalization. Only as a reason to be suspicious of generalizations.

The more aggressive you get about this, the more I'm going to think you must own a few thousand acres of Iowa.

 

Relatively new, I suppose. I was exchanging information with colleagues over ARPANET in grad school. How about you?

Well, if you're not willing to even make the attempt...

Look, if you want to continue believing that misinformation won't be challenged, be my guest. Rather than continuing your mis-direction and irrelevancies, simply admitting that you were wrong about E10 energy content would have sufficed.

 

i think anyone who believes 100% of what they read on the internet is the fool, especially if its from a gov't report. if you believe everything you hear from the govt or even if you believe 10% of what you hear, the whomever you may be, are the fool

 

The only thing worse than that is the fool that picks and chooses what he wants to believe as long as it was what he wants to be right no matter what in the first place.

One can not say the government is wrong all the time and gives out wrong info all the time or one is indeed a fool .

 

My FJ sounded like a diesel if I ran anything but 91. I was relieved to be able to run 89 to save money in my Taco. Now wondering if I should be running 91 in all the vehicles.

 

Myself and 2 friends spent some time keeping track of mileage and Chevron gas gave all 3 of us better MPG vs shell and Texaco. This was a few years ago but impressive either way. Chevron is really good. I use Chevron and if I can't find one, I'll use Shell.

Also, us the lowest grade gas you can THAT WON'T CAUSE ENGINE PINGING. I thought everyone knew this.

I've seen results from motorcycles to cars on the dyno... higher octane that isn't needed actually r'tards performance (Hangover).

This isn't opinion, it's fact.

 

I run Sunoco Ultra 93

My truck loves it

20.9 MPG around town with my V-6

 

And big oil loves you

 

Hey guys, I'm hoping to have my first new Taco next week and was wondering if anyone uses "Marvel Mystery Oil"?
If so, any difference in MPG?

I use it in my GSX-R and '91 Ranger <--- Helps lubricate the motor & Keep things Happy

I've seen an increase in MPG in the Ranger, but let's face it, I wouldn't notice it in the GSX-R, because who drives sport bikes 'easy' these days

 

Our trucks retard timing to prevent knock.

 

Not quite, no.

First of all, you're not going to find much objective research on this because there's no money to be made with the results. Kind of the same reason why you never see much good data one way or the other about taking vitamins. There's lots of crap on the web arguing both sides, but the truth is that a blanket statement either way is plain wrong. This is the reason that octane is argued about on message boards like this ad nauseum.

The only objective attempt to study this that I've seen in recent years was a piece that Car & Driver did with a variety of cars, testing the effect of premium fuel on performance. The result was that a majority of cars didn't experience any change at all, just as you say. One or two of the cars tested did actually get worse, which they couldn't explain. And a couple did perform better. I'm sure you can find the article via Google.

The cars that do better on premium fuel tend most often to be European cars with high compression engines. Many manufacturers over there use very aggressive ECU maps to protect the engine when octane is low. The rated power for these engines is always based on using premium fuel with no ethanol, where the ECU map allows for the most advanced timing and leanest mixture. So what's really happening is not that the car is making more power on premium, but that it makes less on regular. The guys who did the tuning on my Porsche also have a racing program and test fuels regularly because they really can make a difference (even from brand to brand). In most Porsches and BMWs, lap times actually improve on premium. But, again, it's not the gas that does it. It's the engine's defense system that makes the difference. On premium, you're just getting the power you paid for in those cars. Just not all cars.

Finally, octane isn't the only thing that makes premium different. Premium fuels often contain more detergents and other additives and, such as in the case of Shell here in Canada, no ethanol. For some people and for some cars, this is also an advantage even though it has nothing to do with power output, and therefore it's worth paying for for them. On these trucks, it's probably neither here nor there. Toyota builds cars for normal people and normal use, not car nuts.

That said, I run premium in my Taco. I do this because for a few pennies more, I get what the engine designers would have considered 'ideal' fuel for this motor. That's just my thing. I'm sure it's fine without premium, and I don't judge anybody who chooses to run on regular. But in the scheme of things, it's far from the dumbest money I've spent on this truck.

 

Oddly enough, filling up a 91 on my Taco makes it run quieter. Between 87 and 91 on full tank, it's a $5 dollar difference. When i'm not feeling lazy, I add octane additives for less than $5. It's much more concentrated. But when I know that i'm gonna haul people including gears, luggage, and baggage during a long trip, then I fill it up with a 91 along with an octane additive.