I once again learned something new on here. Thanks.

 

The media will grab at any straw, especially on a slow news day. We've all seen that, open any newspaper. Never forget the old saying about believing nothing you read and only half what you see.

If there was much real evidence of E10 causing a large drop in mileage, and given that people already think of ethanol as Satan forced on them by the evil corrupt guvvamint, they'd have a field day.

I just can't find much evidence that supports a huge drop in mileage.

No amount of additives (or lack thereof) will make an instant change in fuel mileage. It would take thousands of miles for anything to occur even under worse case scenario.

As for octane ratings, the only difference from one rating to another is it's resistance to detonation/knock/pinging. That's it, nothing else. If an engine does not detonate on (say) 87 AKI, there is nothing to be gained by using higher octane. If an engine detonates on 87 but does not on 91, then there's a possibility of better fuel mileage and increased power while on 91.

Modern engines use knock detectors to listen for detonation. If it occurs for any reason, the ignition timing is retarded and the fuel mixture enriched to eliminate the problem avoiding engine damage. In turn, this reduces engine power and increases fuel consumption.

Several members (me included) here have tried using 87 in their S-type Jags with the full expectation of noticing reduced power and decreased mileage. Surprisingly, nothing was noted in either category. I get the same highway mileage with 87 as I do with 91.

Since there is apparently no detonation on those cars while using 87 never mind 91, there's little point in using even higher octane (93 or 94) fuels as it's just wasted money.

Not sure why there would be a gain using 93 with an X-type. If so, it infers that there is significant detonation on 91 and that the knock sensor is frequently or constantly interfering. That's just not the way most OEMs tune their engines.

 

If I may and not to overwrite any previous explanations..But in very easy to understand terms;

Octane in higher than lower numbers simply means the burn rate for this higher octane number is SLOWER (means it burns longer) and that makes it harder to ignite too..Thereby it won't pre-ignite before it is suppose to under compression..If the engine is of high compression..you'll need higher octane fuel as is the case with Jaguar engines...

Ethanol is Alcohol..it's even drinkable...it's chemical makeup makes it have less BTU (British Thermal Unit) of heat energy per unit..Compared to Gasoline (not drinkable by the way) which has a much higher BTU rating per unit and therefore has much higher combustion energy level..More bang than alcohol and this means a drop of gasoline will move the engine further than a drop of moonshine will and have more punch to it..That is why in most cases you will see a significant increase in mileage over Ethanol mixed fuels..

Do an experiment;

Pour gas on your hand and light it..It will burn the flesh off almost immediately.

Now pour some Alcohol on your hand and light it..It actually will burn for a long time before you'll feel the heat.

Okay, I don't advocate doing either one..but you get my drift.

 

My pleasure fellow cheesehead

 

I'm only going by what the little "average mpg" thing says on my dash. I understand it is an average, but I reset it each time I fill up, and I drive probably 75% in town/ 25% on highway. By the time I'm below 1/4 tank, I check it, then reset it. Occasionally, I take a trip and there is no town driving. I take all this into consideration. If you, Mikey, are right, and I am wrong -then the little mileage indicator must not be accurate. That may be the case, I don't know. But then a lot of things may not be accurate. Like whether they carefully measure out 10% ethanol into each gas shipment, or maybe someone just dumps in a bucket or two and calls it 10%. Or maybe the specifications for octane ratings and additives are different in Canada than in the US. There are so many variables in today's world, it's usually not a good idea to be so dogmatic.

 

The above is incorrect. All gasoline burns at the same 'speed' (flame front velocity) irrespective of it's octane rating. All gasoline also burns at the same temperature and contains the same amount of energy irrespective of octane rating. It is also not harder to ignite.

To state otherwise demonstrates a lack of understanding regarding detonation.

The SOLE attribute of higher octane fuel is higher resistance to detonate (explode) vs. the desired burning, or deflagration event.

Also- please don't attempt start yet another round of bashing , go look things up instead. Thanks.

 

They're identical all over the world, aside from octane rating systems outside of N.Am. One system (RON) is easily and reliably convertible to the other (AKI).

The in-car mileage computers are known to be wildly inaccurate and barely useful as a even vague reference. The sensors, especially for fuel flow and fuel level are incredibly inconsistent. I can get a 20% variation in average mileage from one tank to another without changing fuel brand or type in any of my cars.

I assumed that you guys were at least measuring and calculating accurately.

 

No ole wise guy of the North..YOU are the one that is totally incorrect (as usual)..

You are not the world's expert on everything as you may think..

If you can read......And all people witnessing this, read this;

Quote:

High octane fuel has a higher flashpoint for a more controllable combustion. It actually burns a little bit slower and it is harder to ignite

and this;

.


and this;


• That's enough I'm bored with Mikey's same old factless, ego inflated rhetoric...you guys can see the FACTS for yourselves..

 

Or- we can use actual credible references, this one from well known fuel manufacturer Whitfield:

Whitfield Oil Company Flame Speed, Octane Number & Horsepower

Here is a similar article from Rockett, another fuel manufacturer

http://www.rockettbrand.com/download...0&%20Power.pdf

Your first reference above is some random guy with the same misconceptions as you.

The second reference from Hemmings by some guy who doesn't understand the difference between pre-ignition and detonation.

The third is (again) some random guy who is as confused as you.

None of them substantiate their statements in any manner, they're just parroting the garbage they've heard.


Now the crucial bit- if you're convinced that you're right, and think that you have a firm grip on the physics of detonation, explain how a slower burning fuel would prevent detonation.

Hint- it won't.

Here's a guy that's got a firm grip on the subject. Please read and learn

Octane is not how fast a fuel burns

Here's another good explanation from a guy how actually understands

http://www.bobistheoilguy.com/forums...&Number=967599

 

Fight nice, guys. You are BOTH right.

It is simply physics that E10 provides lower gas mileage than straight gas. E10 has measurably lower energy available than straight gasoline, the numbers bear this out. We use E10 for lower emissions, not better mileage. It take more E10 to make the same power as a given quantity of gasoline.

The alcohol also makes the gas slightly harder to burn, which, just like a higher octane rating, makes the fuel less susceptible to pre-ignition. Ethanol has a higher octane rating than straight gas, AKI is 99.15, our European brethren see the same stuff as 108.8, since they use RON ratings. Octane has nothing to do with the energy content, by the way, it simply measures the ability of the fuel to burn in a controlled fashion. Higher octane does not mean more energy!

Difference between winter fuel and summer blends? additives in the winter fuel add close to 5% of volume that provides essentially no real energy.

The RATE at which the fuel burns is also a simple matter of physics...and, once ignited, the speed of that burn is pretty much a constant.

 

I've become bored with this too. I guess we just agree to disagree. DPK, you were right! You knew this would not end well. All I need to know, is my cat runs better and gets better mileage with the more expensive stuff. Since it's my money and my car, I will continue to use it. Let's just go back to talking about key fobs and vacuum leaks.....

 

@wa3ra; Thanks buddy, Exactly what I said in post #23..

But this Know-it-all has to always twist the facts as he sees them and never follows the same train of thought in discussions, but only has this insatiable need to correct everyone's opinion or knowledge with what he thinks is the superior intellect of his and has to have the last word...He doesn't read very well either.

 

Let me share as I have learned from a real expert in this industry....That if you have a car that is set up for 87 Octane..then just use that, using higher octane in these type of engines will not usually yield any performance or power benefit. Ultimately the engine will carbon up as the higher octane is not burning off completely before the exhaust valves open and then you get down stream fire and it leads to fouled up catalytic converters as well.

 

No disagreement there. The subject under discussion is how much more E10 does it take to do the work of pure gas. All credible facts and verifiable science support a 3% difference, nowhere near the 10-20-50% some people here have proposed.

Ethanol is less susceptible to detonation, not pre-ignition. The two are very, very different phenomena that must not be confused. Assumption that they are the same thing leads to myths and misconceptions.

Here's a good explanation

Engine Basics: Detonation and Pre-Ignition by Allen W. Cline

This is true too, and if we were using 100% ethanol fuel, that would be the actual octane ratings. Being that E10 is a blend of gasoline and ethanol, the net octane rating is as posted on the pump- 91 or 93 AKI as being discussed above.

Agreed on both points and the key word is 'burn'. Detonation is an explosion- which is what can damage engine and must be controlled.

 

Another myth..........

 

By the way, I did independent testing of fuels in the lab for a while; road fuels, av-gas, racing fuels (like I said, av-gas...at that time. now racing fuel is unleaded)...and additive packages.

You would be surprised how few actual refiners there are, and almost all brands come from the same places. The big "S" rolls their own, but many jobbers buy from them, too.

By the way, E10 actually makes MORE power under some specific conditions, but we don't spend all of our time at 2800 rpm and under perfect adiabatic conditions.

 

It won't carbon the engine itself, but it sure will ruin a convertor. That is assuming an iso-octane rich enhancer; aniline oil, for example. Obviously TEL, as well...but we don't put that in any fuels anymore.

 

There's little difference between a 'normal' compression (requires 87AKI octane) and high compression (requires 91AKI) engine and exhaust system that would explain why today's high octane fuel would damage a low compression vehicle. In some cases the converters are identical.

Leaded fuels are excepted as you noted- that would ruin any converter in short order.

 

I guess I opened a can of worms which this tread. A good healthy exchange of ideas is always good for the mind.
I am reporting my second tank of gas this time the mileage came out to be 20.5 mpg. A little lower but still better then I got before switching to Shell 93 and reinstalling the K&N filter which I think has nothing to do with the increased mileage as a lot of K&N owners state they lose a few miles to the gallon with this filter.
Question is there 95 octane out there? I live in New England and the highest octane is Shell 93 and there are not a lot of Shell stations around. How about other parts of the country?

 

We have 94 at some stations in Canada, but I question why. I know of no car that needs/gets benefit from anything higher than 91.