Do you guys every fill your CLKs up with 87 regular,, and if u do,, is there any problems with that,, And also do u guys feel a difference when using supreme 91 octane,,
on the gas lid it says premium only.. that is why i ask

 

origally posted by E-klasse in another topic....he's pretty much saying only use 91 octane or higher but read it, there's good info...


Check your owner’s manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars, old cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

Listen to your car’s engine. Knock occurs when cylinder pressures are high. It is normal for an engine to ping a little at full throttle because cylinder pressures are very high at full throttle. Engine knock, however, should not be ignored since it can result in serious damage to the engine. High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high. Persistent knock can lead to engine damage and carbon buildup.

Some things to note: Damage can occur during heavy load situation like climbing hills, pulling loads, racing or most Under wide-open-throttle (WOT) conditions. The EEC is not looking at the knock sensor because the engine is simply making too much noise for the knock detection strategy to filter out the knock signal from the noise. Timing and fuel for WOT is derived from lookup tables that are vectored primarily by crankshaft RPM and engine coolant temperature, and to a much lessor degree by the mass air signal.

One web site puts it this way:
Octane Rating - A number that represents the resistance of gasoline to premature detonation when exposed to heat and pressure in the combustion chamber. Such detonation is wasteful of the energy in the fuel and potentially damaging to the engine.

Engine designers assign an octane number rating (ONR) to the engines they design and it is the octane number at which at engine will run without knocking. Many factors affect the ONR, including compression ratio, ignition timing, fuel/air ratios, cylinder head temperatures, and combustion chamber design.

Compression ratio has the largest impact on both ONR and engine efficiency… higher compression results in a more efficient engine and a higher ONR. Retarding the engine timing, running either rich or lean, reducing cylinder head temperatures, and using swirl type combustion chambers all reduce ONR.

Octane below ORN causes pre ignition. Pre ignition occurs too soon before the piston is at top dead center, you place a tremendous strain on the engine… the forces of burning happen too early and press against the piston while it is still traveling up. Third, hot spots develop in the engine. The cylinder head is designed to take maximum heat, and maximum flame duration.

The pistons normally have the shortest period of contact with the flame front, but if the gasoline ignites close to the piston, say, due to a carbon deposit, then the piston is subject to temperatures for which it was not designed.

I Like the way this Engineer puts it when asked about octane:
"If the fuel is too low octane, it may spontaneously ignite before the spark plug fires due to thermal rises from the heat of compression or from hot spots in the cylinder itself. This kind of ignition is called pre-ignition (as opposed to knocking) and is a pathological case which will just turn an engine to scrap.

Pre-ignition can damage an engine before you finish reading this sentence. To reiterate, what we're really concerned with is called "knock" and that's the spontaneous ignition of the fuel-air mixure ahead of the flame-front as a result of the rise in cylinder pressure caused by the onset of ignition (caused by the firing of the spark plug).

An engine's efficiency is in direct proportion to its compression ratio. Unfortunately, raising the compression ratio means we need to protect against knock/detonation. How do we do this? Use higher octane fuel! "
__________________

 

In Canada, we only have 3 flavors of CLK, CLK320, CLK500 amd finally the CLK55. Accordning to the owner manuals, all these CLK demand premium octane (91) gasoline.

I, for one, will not put any less in my CLK. Besides the engine damage, I think it's also not good for the oxygen sensors.

 

While I don't own a gas MB, I do have a gas volvo and while they say it needs high octane fuel I've always used regular in it, 27k miles, with no apparent ill effects, the computer takes care of any knocks and if there is a loss of performance, I've never noticed it, the car runs fine, YMMV

 

i jsut put in 87 octane in my car well my friend did. no ill effects so far.