Interesting fuel....

[freeatlast]

Originally Posted by trollbait

A larger compression ratio can provide better performance and efficiency. So higher octane can improve fuel economy in an engine over lower, if that CR is high enough to take advantage of it.

Octane lower than 87 is available in areas of high elevation, because of the thinner air. Using it in a naturally aspirated engine in those locations isn't an issue. The engineers would have designed a safety buffer into the system if a car with 85 in its tank goes down to a lower elevation, or if the gas happens to age.

No, octane cannot provide better MPG. Octane is an anti knock compound not a BTU enhancer. It is the higher compression that makes more HP not octane. The octane only allows the right engine to develop the most from the gas it is made for. The same with regular. Use the wrong grade and you can lose MPG and performance along with wasting money.

The manufacturers knows their vehicles ship to higher elevations. They do not build special vehicles for special elevations. if the book spells out 87 as a min. that should not be taken lightly. While knock will be small on 85 octane and not noticeable it will be there and while it will take some time to cause damage it will cause damage. For the difference in price it would be wise to follow the manufacturer's recommendations.

Here is a link about octane. Premium vs. Regular | Car Talk


https://cars.usnews.com/cars-trucks/...gular-gasoline

[freeatlast]

Originally Posted by 14Corolla

Octane is not an additive. Octane is the value of how well a liquid burns, rather than explodes. Nitro Glycerine is extremely low octane. Kerosene is very high octane.

You give absolutes that are completely irrelevant. You completely ignore why the octane is what it is. It is, because of elevation. At low elevation the octane is one thing. At higher elevation, they lower the octane to match the low elevation performance. This is decided by the refinery. My playing around with octane is trying to better match my octane to my elevation. That is all.
And yes, at stations in the large city here. I obtained better mileage by mixing premium and regular to up the octane on the regular. I consider doing it with different stations regular outside of that city. This stuff is doing pretty darn good for me now. It might just work out as playing around. ????

Claiming that kerosene has an extremely high octane rating tells me you have no clue what octane is. Kerosene has an octane rating of about 15. I challenge you to try and run it in your vehicle and see what happens.

As your claim about nitroglycerin that is beyond silly. Nitroglycerin is what dynamite is made of. It is NOT a fuel. Perhaps you meant nitrous oxide, but it is not used for octane but rather the ability to hold Oxygen so more fuel can be added.

The truth is that ethanol has a higher octane than gas. They use it to increase the octane rating but it also lowers the MPG and performance.

You can do what you want with your vehicle but there is no monetary benefit in using a higher octane than the manufacturer calls for.

https://www.scientificamerican.com/a...ion-premium-g/

[trollbait]

You seem to have some misconceptions.

Octane isn't some type of additive. It is a measurable property of a fuel along the lines of its boiling point and viscosity. It is a measure of how well in resists igniting from heat and pressure, and thus causing knock. Two different octanes can be mixed to provide a third. That is how gas stations provide midgrade. No refinery makes it, and mixing regular and premium on your own is likely cheaper than buying that octane.

Air density also plays apart in whether knock will occur. The lower the density, the thinner the air, the less of it that gets sucked in on the fuel stroke, which means a lower pressure, and less heat when the piston compresses it. So when driving at higher elevations there is no harm in using lower octane fuel with a naturally aspirated engine.

I said knock sensors aren't miracle workers, but they are darn good at their job. If a lower than recommended octane is used, the sensors can detect the beginning of a knock, and dial back the ignition timing. Parents had a 2004 Acura, and put over 120k miles on it without issues. The manual recommended premium, but they only used regular. Yes, that meant the car didn't do its best in power output or efficiency, but the V6 still returned 30mpg on the highway.

Ethanol lowers fuel economy because of the lower energy content, but if flex fuel engines weren't based on low octane using designs, and had a higher compression ration to take advantage of its high octane, the fuel economy drop would be less. As you can extract more of the fuel's energy during the power stroke.

Some engines can take advantage of a higher octane fuel than what the manufacturer says. Engines are now designed for the global market, and much of the first world have slightly higher octane for their regular gasoline. Since premium or midgrade on a window sticker can hurt sales for most car models, the company says it takes regular. they don't change a thing on the engine, and just let the knock sensors and computer do its job while running US regular.

I have tested higher octane fuels in my car, and do get better fuel economy, because the engine was designed for European fuel.

[freeatlast]

Originally Posted by trollbait

You seem to have some misconceptions.

Octane isn't some type of additive. It is a measurable property of a fuel along the lines of its boiling point and viscosity. It is a measure of how well in resists igniting from heat and pressure, and thus causing knock. Two different octanes can be mixed to provide a third. That is how gas stations provide midgrade. No refinery makes it, and mixing regular and premium on your own is likely cheaper than buying that octane.

Air density also plays apart in whether knock will occur. The lower the density, the thinner the air, the less of it that gets sucked in on the fuel stroke, which means a lower pressure, and less heat when the piston compresses it. So when driving at higher elevations there is no harm in using lower octane fuel with a naturally aspirated engine.

I said knock sensors aren't miracle workers, but they are darn good at their job. If a lower than recommended octane is used, the sensors can detect the beginning of a knock, and dial back the ignition timing. Parents had a 2004 Acura, and put over 120k miles on it without issues. The manual recommended premium, but they only used regular. Yes, that meant the car didn't do its best in power output or efficiency, but the V6 still returned 30mpg on the highway.

Bottom line paying for a higher octane than called for will NOT give you more power or MPG. That the point.

[Draigflag]

Question for you: Shell "fuel save" has been designed to do exactly that, and given the fact they wouldn't be allowed to name the fuel such a thing unless proven to do exactly that, what is added or subtracted from the fuel to give better fuel economy?

[freeatlast]

Originally Posted by Draigflag

Question for you: Shell "fuel save" has been designed to do exactly that, and given the fact they wouldn't be allowed to name the fuel such a thing unless proven to do exactly that, what is added or subtracted from the fuel to give better fuel economy?

Never heard of shell fuel save, Also what meant by "exactly that."

[trollbait]

Originally Posted by freeatlast

Bottom line paying for a higher octane than called for will NOT give you more power or MPG. That the point.

Yet my Sonic calls for regular, and I do get better power and MPG when using higher octane.

It comes down to the engine design, and why the manual calls for the octane that it does.

[14Corolla]

Originally Posted by Draigflag

Question for you: Shell "fuel save" has been designed to do exactly that, and given the fact they wouldn't be allowed to name the fuel such a thing unless proven to do exactly that, what is added or subtracted from the fuel to give better fuel economy?

Advertising ...

[R.I.D.E.]

Originally Posted by freeatlast

Yes they do have an anti knock sensor, but the sensor is not infinite. It is limited to what the lowest octane rating that the manufacturer recommends. That is why they warn you. They can only adjust the timing so far. Any octane below the recommended is taking a chance of internal knock with head gasket and/or head failure.

While there may be "limits" to the range of spark retardation when engine knock is detected, it is not limited to recommended fuel octane. In engines where the compression or other specifics of design absolutely require premium, IE turbocharged ultra high performance engines, they will not "disintegrate" if you use regular fuel, but you will notice significant loss of performance.

If that were the case you would see manufacturers-dealers refusing to honor a warranty if the customer had EVER used regular fuel in the vehicle.

30 years in the auto business, 60k hours of tech work, intimate knowledge of systems and their functions here. From the late 1960s to the end of the twentieth century, when emissions systems went from primitive to fairly sophisticated.

Today, with direct injection, you can have multiple injections, while combustion is occurring, which prevents knock altogether and slows down the combustion event to allow more pressure later in the downward movement of the piston, when the "leverage" of the big end of the connecting rod and crankshaft journal is better for power transmission.

Not as late as 90 degrees after TDC since the pressure levels drop off rapidly by then but closer to the 90 degree point.

Preignition or detonation, called spark knock, is when the mixture ignites before the piston reaches top dead center, the flame front collides with parts of the combustion chamber and then reflects back into itself.

Multiple injections, in a single combustion event, require direct injection into the combustion chamber as well as ultra high injection pressures of 3000+ PSI eliminate any possibility of knocking, as long as everything is working properly.

[Draigflag]

Originally Posted by freeatlast

Never heard of shell fuel save, Also what meant by "exactly that."

You don't get it in the US, it's too fancy

Originally Posted by 14Corolla

Advertising ...

Well a third party carried out some tests over 5000 miles and it does give better fuel economy, they would be sued over trades description act if it didn't. I googled it, found the usual marketing nonsense, apparently it has better lubricating properties that give an even coverage over the pistons and more detergents etc etc...