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Discussion Starter · #1 ·
An acquaintance runs a Land Rover site. He's been a mechanic for many years. He's researched the facts and myths of octane as I have. Here's what he published on his site about octane:

Everything You Always Wanted To Know About Octane

July 20, 2002 By: Steve

Gas, you say? What's there to know about gas? Actually there's not much to know about gas, but the little that most people know about gas is wrong. The misperception about the use of higher octane for more performance is the most common. I'll discuss the other misconceptions later.

First off- Octane. Race cars and high performance vehicles have higher compression engines and more advanced ignition timing. This higher compression can cause premature detonation (relax guys, it happens to everyone once). To remedy the premature detonation a slower burning fuel is used. Higher octane numbers mean that the fuel burns slower. The slower burning fuel can be compressed at a higher ratio without as much fear of deadly premature detonation, commonly called "pinging." Pinging will definitely ruin your engine. In modern engines with aluminum pistons this is an absolute engine killer. With modern replacement engines starting at $2000 + installation for cheap cars and up to $20,000 for some higher end cars, it's not something to ignore.

Standard engines are calibrated for regular lower octane fuels. If you put a slower burning fuel (remember, slower fuel is higher octane), then what often happens is that all the fuel is not burned. The incomplete detonation leaves behind carbon deposits that wreak havoc on the valves, piston tops, EGR and PCV systems. I've often heard people claim that they've used premium in a car that didn't require it, but now if they try to use regular they get a pinging detonation problem. That is a self-induced malady. When enough carbon builds up in the combustion chambers, it effectively raises the compression by making the chamber smaller. Remember the whole thing about high compression requiring high octane from the earlier paragraph? If you have already made this common mistake, there's a way to fix it without having to admit you screwed up. Take your vehicle immediately to a competent repair shop and ask for a carbon depletion system. The two I'm familiar with are the Bilstein and BG engine flush systems. They run a hot detergent through the engine and remove the carbon buildup. Adding a fuel system cleaner like BG 44K to the gas tank a couple times a year is a great idea. The $3 stuff you get at the gas station is merely alcohol- you want a real cleaner.

Here's what this all means:

If you have a vehicle that is designed for 87 (regular) octane, then use it. They spent millions of dollars designing the engine, fuel system, sensors and computers- don't second guess the manufacturer's ability to determine which gas is best for it. I haven't seen a car yet that is designed for regular that can adapt to premium. If it could adapt to premium, it probably would have been designed to be a premium engine from the start.

If you have a vehicle that is designed for 92 (high) octane, then use it. The engine design was made for it. If you have to, you can often use lower octanes for short periods of time. The engine has a knock sensor that can detect "pinging" and will adapt the timing of the ignition system to protect the engine from damage. The result is lower performance.

So, it's a one way street. You can put regular in a premium vehicle, but you can't put premium in a regular vehicle. There is a very very rare exception to this rule. There have been some cars that were designed for premium fuel, but were then detuned and calibrated for regular low octane. These engines will adapt to premium and operate just fine. Is the Freelander one of these? I'm not going to risk my engine to experiment.
 
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Discussion Starter · #4 ·
From ABC's 20/20, "20/20 Takes On Summertime Myths":

The Price Is Premium, But 'Gas Is Gas'

When you head out on vacation this summer, you'll probably spend big bucks filling your car's gas tank, while griping about the price. But a lot of you who are complaining could be spending less for your gas.
You have a choice of gas at the pump. The price of 93 octane premium is more than regular 87 octane — about 20 cents more per gallon at many stations. Because premium costs more, a lot of people think it's better for their cars.
People told us premium gasoline gives them better gas mileage, more power and cleaner engines.
Regular gas, one woman told "20/20," "leaves a lot of gunk in your engine … That's what my daddy taught me."
But her daddy — and many of you who buy premium — are wasting your money.
NASCAR driver Joe Nemechek knows this. "Believe me, I've pumped gas in from about every gas station there's been in my personal cars. Whether it's around town or on vacation or wherever, you put the regular in there it keeps on running," he said. The NASCAR drivers, mechanics, and car makers will tell you that for 90 percent of the cars sold today, high octane is no better than regular gas. It won't give you better mileage, more power or a cleaner engine. NASCAR crew member Lisa Smokstad told us what every expert told us.
"It is a myth that cars run better on premium gas," she said.
Some cars do need higher octane — older cars that knock, and cars with high-compression, high-revving engines like Ferraris, Bentleys, Jaguars, Acuras, Mercedes and Corvettes.
But 90 percent of new cars don't need it — check your owner's manual.
The car manufacturers and every car expert we consulted told us that for most cars, high octane is a waste of money. Even the gas companies that sell the high-octane fuel — and make more money off of it — admit most people don't need it. But they don't go out of their way to tell you that.
Once you've figured out which octane to buy, does the brand matter? Are the well-known national brands better than the no-name brands, which are usually cheaper?
People we spoke to gave similar reasons for buying name-brand gasoline that they gave for buying high-octane gas. They believed the national brands were higher quality, and better for their cars.
But they may not know that all the gas, brand name and generic, comes from the same refineries. Brand names do use different additives, but it doesn't make them better for your car.

In 1996, the Federal Trade Commission forced Amoco, which denied any wrongdoing, to stop claiming in its ads that it was better than other brands without scientific evidence to back it up.
"It's a myth that brand-name gas is better than a no-name gas," said mechanic Dave Bowman, co-host of "Two Guys Garage" on cable TV's Speed channel.
"It doesn't make any difference whether you're buying a branded product or a no-name product," he said.
"The only difference is price."
The NASCAR drivers agree about that, too. "It's a myth, you don't need the high-octane gasoline, you don't need the, the name-brand stuff," said driver Jimmie Johnson.
Some of the fans have figured that out.
One man summed it up nicely for us. "The manufacturers and the gasoline dealers, they all want you to buy that expensive stuff. It all runs on the same stuff. Gas is gas."
 

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Thanks for that Brad, I have had what someone called 'pinging' in my car and they told me to occasionally fill with high octane gas, have done it once but will be reverting back to standard - like your mate says - don't second guess the manufacturer who has spent the millions and done the homework! So my Caliber may need the timing looked at? The emission light comes on when I start it up.........can't believe it, the last repair to my previous car was for the emission light coming on!!!
 

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Discussion Starter · #6 ·
That pinging is a known issue, and your dealer should have the TSB for fixing it.;)
 

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That pinging is a known issue, and your dealer should have the TSB for fixing it.;)
Hey, I live in Perth, Australia - have only had the car a couple of months and was a demo with 1500km on clock - dealers here not too helpful but I might try calling them tomorrow to sound them out...........american made car, better service etc in america!!! :eek:
 

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What about 89 Octance: Unleaded Plus?

There seem to be a reliable information regarding with 87 and 93 octance. Am I blind or something that I do not see any of 89 octance, Unleaded Plus?

Once a month I filled with Unleaded Plus whenever Chevron have "weekend" gas sales that sells 2-3 cent more than Unleader Regular or when I admistrate Chevron's Techron Fuel System additive in once every 6 or 12 months. ( My concern was that when I use Chevron's Techron and use Unleaded regular that might lower octance alittle, Maybe 86.5? lol.... So I use plus to keep it 87-below 88. A perfect formula? )

Mechanic, Please educate us whether it is ok or not to use Unleader Plus on few occassionals?

Thank you!!! :worshippy:
 

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Discussion Starter · #10 ·
I was at the bookstore yesterday looking at car magazines, and books. Came across a book on car maintenance that put it this way:

"Treating your car to a higher octane once in a while made sense in the 1970s, but only serves to damage engine components in today's cars."
 

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I usually throw a tank of premium in every 3-4 tanks because that is what my dad always said to do.
Looks like that was money thrown away. Thanks for the good advice.
 

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An acquaintance runs a Land Rover site. He's been a mechanic for many years. He's researched the facts and myths of octane as I have. Here's what he published on his site about octane:

Everything You Always Wanted To Know About Octane

July 20, 2002 By: Steve

Gas, you say? What's there to know about gas? Actually there's not much to know about gas, but the little that most people know about gas is wrong. The misperception about the use of higher octane for more performance is the most common. I'll discuss the other misconceptions later.

First off- Octane. Race cars and high performance vehicles have higher compression engines and more advanced ignition timing. This higher compression can cause premature detonation (relax guys, it happens to everyone once). To remedy the premature detonation a slower burning fuel is used. Higher octane numbers mean that the fuel burns slower. The slower burning fuel can be compressed at a higher ratio without as much fear of deadly premature detonation, commonly called "pinging." Pinging will definitely ruin your engine. In modern engines with aluminum pistons this is an absolute engine killer. With modern replacement engines starting at $2000 + installation for cheap cars and up to $20,000 for some higher end cars, it's not something to ignore.

Standard engines are calibrated for regular lower octane fuels. If you put a slower burning fuel (remember, slower fuel is higher octane), then what often happens is that all the fuel is not burned. The incomplete detonation leaves behind carbon deposits that wreak havoc on the valves, piston tops, EGR and PCV systems. I've often heard people claim that they've used premium in a car that didn't require it, but now if they try to use regular they get a pinging detonation problem. That is a self-induced malady. When enough carbon builds up in the combustion chambers, it effectively raises the compression by making the chamber smaller. Remember the whole thing about high compression requiring high octane from the earlier paragraph? If you have already made this common mistake, there's a way to fix it without having to admit you screwed up. Take your vehicle immediately to a competent repair shop and ask for a carbon depletion system. The two I'm familiar with are the Bilstein and BG engine flush systems. They run a hot detergent through the engine and remove the carbon buildup. Adding a fuel system cleaner like BG 44K to the gas tank a couple times a year is a great idea. The $3 stuff you get at the gas station is merely alcohol- you want a real cleaner.

Here's what this all means:

If you have a vehicle that is designed for 87 (regular) octane, then use it. They spent millions of dollars designing the engine, fuel system, sensors and computers- don't second guess the manufacturer's ability to determine which gas is best for it. I haven't seen a car yet that is designed for regular that can adapt to premium. If it could adapt to premium, it probably would have been designed to be a premium engine from the start.

If you have a vehicle that is designed for 92 (high) octane, then use it. The engine design was made for it. If you have to, you can often use lower octanes for short periods of time. The engine has a knock sensor that can detect "pinging" and will adapt the timing of the ignition system to protect the engine from damage. The result is lower performance.

So, it's a one way street. You can put regular in a premium vehicle, but you can't put premium in a regular vehicle. There is a very very rare exception to this rule. There have been some cars that were designed for premium fuel, but were then detuned and calibrated for regular low octane. These engines will adapt to premium and operate just fine. Is the Freelander one of these? I'm not going to risk my engine to experiment.
Looks like my worst fears have come true. The engine pinging has comenced!! I switched back to 87 fuel, but I'm afraid it is too late, now I will look into getting the engine flushed a few times to fix this, if that will even fix it! I hope that takes care of it and in the future I'll save premium fuel for my SRT-4 when it comes out!:4-jump2:
 

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In GM PCM calibrations they have two timing tables, high and low octane. They also have a function of "knock learn". The PCM tries to run the high octane table. As the knock sensor(s) detect knock at various rpms and load it learns this and and starts migrating the timing toward the low octane table only at the points of knock learned. The PCM is then using a blended version of the high and low timing tables. If no more knock is detected, the timing starts migrating back up toward the high table. Migrating back up takes far more time then migrating down. Most GM's will benefit from higher octane gas, especially in areas where there is knock with lower octane gas. Is it worth the .20/gallon difference? NO

Now I would assume that all manufacturers use this type of tuning to compensate for bad tanks of gas, altitude, and weather changes. Hopefully my tuning software will support Chrysler soon so I can see how these are set up.
 

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In my country we have 91 and 95 octanes.

I fill my tank with 95.

I fill the tank with 3 US$, yes, the water here it's more expensive than gasoline.
 

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So I don't get it. When I go premium, I get atleast 50KMs more per tank, so obviously its more efficient to drive with premium gas. The extra cost is balanced by the fact that I get another 50Kms on a tank. So I don't save or lose money on it, it just means I can drive longer on a tank (I"m a commuter, 60kms each way to work). So I don't know why I hear people saying that high octane gas doesn't improve mileage or economy... that just doesn't make sense. I do get better mileage with it.

My question is, does it harm the engine by putting premium in it? My parents regularly put premium in for long hauls, just cause you can drive longer before filling up.
 

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Discussion Starter · #17 ·
So I don't get it. When I go premium, I get atleast 50KMs more per tank, so obviously its more efficient to drive with premium gas. The extra cost is balanced by the fact that I get another 50Kms on a tank. So I don't save or lose money on it, it just means I can drive longer on a tank (I"m a commuter, 60kms each way to work). So I don't know why I hear people saying that high octane gas doesn't improve mileage or economy... that just doesn't make sense. I do get better mileage with it.

My question is, does it harm the engine by putting premium in it? My parents regularly put premium in for long hauls, just cause you can drive longer before filling up.
I suggest you start from the beginning of this thread. Your answer is already in this thread.;)
 

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Thanks, I read the top. It conflicts with what I've experienced. I'd like to know if there are any mechanics out there that can testify that it causes issues. Its a fact that I get more mpg then when using regular. AND if the engine compensates anyways for the 'pinging' (though I don't find mine does that) they why not get more mpg out of a tank of gas? I've read it all but it doesn't make sense in real life, plus all the people who posted saying that their dads always put premium in every once and a while. Are all saying that was actually counterproductive? And it harmed the vehicles. computers have been in cars since the 90s anyways.. So ya, I haven't been convinced that its bad for your car, or that as the original post states, that premium lowers the efficiency of the engine somehow...
 

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Discussion Starter · #19 ·
Thanks, I read the top. It conflicts with what I've experienced. I'd like to know if there are any mechanics out there that can testify that it causes issues. Its a fact that I get more mpg then when using regular. AND if the engine compensates anyways for the 'pinging' (though I don't find mine does that) they why not get more mpg out of a tank of gas? I've read it all but it doesn't make sense in real life, plus all the people who posted saying that their dads always put premium in every once and a while. Are all saying that was actually counterproductive? And it harmed the vehicles. computers have been in cars since the 90s anyways.. So ya, I haven't been convinced that its bad for your car, or that as the original post states, that premium lowers the efficiency of the engine somehow...
I used to think the way you do. All the info that shows no practical gain, and possible damage to the "New" engines comes from oil companies, car companies, and reputable mechanics. You can do what you want, and you can feel justified by your [unscientific] seat-of-the-pants evaluation, but I prefer to follow what the experts say.

I might add, it wasn't until you rekindled this topic that I realized that my using mid-grade gas in my Ram for two years, is probably why I couldn't use regular in it anymore. It got so bad that the last year I had it required me to use premium to stop the pinging. It was probably all the carbon buildup causing pre-ignition.

Thanks for jogging my memory.;)
 

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I'm in the same boat as Micah. I drive the same way, every day, to and from work all highway and I get more mpg per tank - even with 89. If I use regular I can barely make it to 600km on a tank, and when I pull in to get gas I literally have 3-4 litres left.

On 89 I hit 600km easily, and when I fill up I have around 9-10 litres in the tank.

My drive times itself nicely to filling up at the same gas station as well, I even go so far as to use the exact same pump too (I'm there at 6am and I'm in a small town so it's usually empty).

I don't know if it's the detergents they have, but the Shell stations by me say that every grade has the detergents in them and the top octane has V-Power. If I use that the car is really peppy but not much change in mpg from 89 to whichever shell's top grade is (91 I'm assuming - I don't really pay attention to it as I rarely get it).

Also, this thread reminded me of my ol '95 cherokee which I used 89 octane religiously. It sat parked at my parent's place for about 4 years, never moved. Started right up when I decided to check it as well, but the strict Castrol Syntec oil changes probably helped that.
 
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