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What kind of gas you put into your MZ3


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Discussion Starter #1
I know owners manual suggests regular, but may be someone thinks otherwise...
 

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This has been discussed before. Please do a search before posting. To make a long story short. The answer is regular 87 octane is what you should use.
 

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87 for me too...no need to use higher octane right now until we mod our cars lol ;), but i think i may try 89 one of these days or 91 just for the hell of it hahaha....
 

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Damn Canadians... we only get 85, 87, and 91 octane.

Although there is a race gas station in Co that carries 91, 100, 105, 110, 115 leaded at the pump.

105 octane is $4.99/gallon.
 

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whoa ... i never even heard of 85 rich haha...over here in cali we get 87 89 and 91
 

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Yep, lame eh. Back when I had a 91 Corolla (first car) 85 octane gas would give me almost 40mpg. Geez, that thing would last at least 2-3 weeks on one tank.

Next time Im at the pump, Ill snap a pic for ya.
 

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I've seen 85 a few times. There is 85 octane gas around. Plus I believe 87 is downrated to 85 at higher altitudes. So if you travel to towns in the Rockie Mountains, you'll see 85 on the pumps.

As to which gas to use, if a car is tuned for 87 and the ECU isn't reprogrammed for higher octane, then in nearly all cases a car will have less performance with 91 or 93.

Just pumping in 91 or 93 in hopes of better performance is a waste of money.
 

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I still can't get over 85 - is there a (scientific) reason for this at higher altitudes?

Now as far as 89/91/93 goes, it's a waste in NA where our engines are designed for 87. Some people believe that it can actually harm the engine to use higher octane gas...
 

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Yeah I've never heard of 85.

And yep, as dinu said, no reason at all to run 87. In fact, running higher octane in an engine that can't take advantage of it very well may reduce power.
 

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Dinu, I'm no expert on it but from what I can remember the reduced oxygen in the mountain altitudes like that can call for lower octanes because they burn easier with the reduced oxygen mix. As you climb higher in octane the amount of oxygen coming in to mix with the fuel to burn at optimum levels (or at least as good as it can) goes up.
 

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MZ6ZoomZoom said:
Yeah I've never heard of 85.

And yep, as dinu said, no reason at all to run 87. In fact, running higher octane in an engine that can't take advantage of it very well may reduce power.
I'm assuming that you meant to say either "no reason at all to run anything other than 87" or "no reason at all to run 87+", correct?
 

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Octane rating is basically a measure of the resistance of the gas to burn. The higher the octane, the more resistant the gas is to burning, meaning it needs higher combustion temperatures to do so. Let's look at an example:

The 3 is designed to run on 87 octane. Using gas of this rating, the engine is designed and programed to completely burn all of the gas in the combustion chamber at the time of ignition, giving you the best performance (clean burning is good). Now, let's say you've become a victim of advertising, and you think you're doing your car a favor by dumping in the ocassional tank of 91 because you think it has better detergents (it doesn't). 91 octane is more resistant to burn. Because of this, when your sparkplug fires, it's not making enough heat to burn all of the gas in the combustion chamber. As a result, you do not get a clean burn nor optimized power. Instead, you now force unburnt fuel through your engine and into your exhaust/emissions components, causing carbon build up, and reducing power, efficiency, and the life of your engine and emissions parts. Some "favor", eh?

So, if that's the case, why is higher octane available? Here's why: some engines are programmed to burn at that higher temperature. In those cases, putting in a lower octane fuel that burns at a lower temperature will result in pre-detonation, also refered to as detonation, knock, or "pinging". The fuel is so prone to burn that it combusts before it's supposed to, either in part or in whole, thus exerting dangerous stress on pistons and rods that are not positioned to receive the forces yet. Detonation is the most damaging thing you can do to your engine. On my turbo Miata, for example, I don't run anything less than 91, and usually stay with 93 or 94. Turbocharging heats up the intake charge, so the incomming air is hotter to begin with. On top of that, I have an auxilary engine computer that modifies my spark timing, so I can take full advantage of high-octane fuels, burn them completely, and get the best efficiency out of my engine. I can also retard timing in the event that I must use a lower grade of gas.

Ambient conditions also play a factor. I can't imagine this would be the case, but if you experience any detonation in the summer months, there's a good chance that it's because the air is warmer, not to mention the engine takes some heat soak, so combustion chamber temps might be a slight bit higher, causing pre-detonation. If you find this to be the case, use the next grade octane fuel... though I think the factory knock sensor would eliminate this scenerio.

Then, of course, there are 190 Octanes, which are slush type drinks which contain Everclear... a 190 Proof alcohol. Those you may use at any time, and liberally, too, since the only "knocking" you have to worry about is the pounding in your head the next morning... ;)
 
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