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Anyone know what the recommended fuel will be for the naturally aspirated engine? 87, 89, 91+ ?
Its a Mercedes thus I dont think anything but Premuium would be required unless of course it's a diesel ?? I had the C Class and that required Premuium 91+ grade so I cannot see the CLA using Regular gas ??
 

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Dan's Focus ST is a turbo engine and 'suggests' regular... however, once tuned via aftermarket tuners they require minimum 93 octane. So, I'm guessing MB will tune it for regular gas and hopefully bump up the timing/boost if it detects zero knock and premium fuel.
I didn't know that (ST/regular gas)Interesting. It would be a good move to run on regular, with crazy gas prices and all
 

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I didn't know that (ST/regular gas)Interesting. It would be a good move to run on regular, with crazy gas prices and all
Yah... a big misconception a lot of people have with octane is that they assume the higher the octane the more power you make. Its actually the opposite.

You'll make more power running a lower octane fuel as long as you aren't getting any knock.

Unless you increase timing, and/or boost then the higher octane is worthless.

In other words, you want the lowest octane you can run without detonating and you'll make the most power.
 

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Yah... a big misconception a lot of people have with octane is that they assume the higher the octane the more power you make. Its actually the opposite.

You'll make more power running a lower octane fuel as long as you aren't getting any knock.

Unless you increase timing, and/or boost then the higher octane is worthless.

In other words, you want the lowest octane you can run without detonating and you'll make the most power.
I guess that I'm one of "a lot of people" who think that you can get more useful energy (and power) out of high-octane fuel than low. High-octane gasoline actually burns more slowly than low and is more effective at transferring energy from the expanding gases to the pistons and crankshaft. Of course, the spark timing has to be set up right to take advantage of that. I used to pilot my own plane quite a bit, and the guys who raced cars at the local track would come by the airport to purchase the 100-octane gasoline available for the aircraft. They ran very-high-compression engines and needed that octane to be able to make use of them.

Forced-induction (turbo) engines have a higher effective compression ratio than combustion-chamber geometry would suggest and, in my experience, can make the most power when fed high-octane fuel. If they are not, sensors in modern engines will pick up the knocking and retard the spark until the knocking stops -- significantly lowering power output.

A little known fact (at least in the US): It was 100-octane gasoline produced by Shell Oil in Texas that gave the Spitfire and Hurricane fighters a decisive power advantage over the Luftwaffa in the "Battle of Britain" in 1940. Their engines were, of course, designed and tuned to take advantage of the fuel.
 

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LennyR,

If you read what I wrote I mentioned that if you can run more boost or more timing (or have higher compression) -- ie, something that can actually take advantage of the higher octane then you can produce more power.

However, if you take a regular old engine and an ECU that is setup for 91 octane and throw 100 octane in there without changing anything -- its going to run worse, not better. And get worse gas mileage.

To qualify my statements, I've been racing cars for a long time. I used to add Tolulene/Xylene to my gas tank on my Turbo Buick so I could increase boost and keep knock away. I understand minimum octane requirements and when higher octane will benefit you, and when it won't ;)

I've had a 10 second Turbo Supra, currently own a 10 second GT-R and I've owned 12 second Talons, 13 second Buicks and lots of stuff in between ;)
 
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