i don't know where you folks are getting your numbers from but here the spread is at least 10% on the price of regular versus premium. If you are going to provide facts so others can make an informed decision please try to keep them accurate. Wild guesses and wayward opinions don't help anyone. Reading this reminds me of my neighbor who insists the nissan truck he just bought gets 33 miles to the gallon when everyone else with that model gets 18. I've run 87 octane in my c280 a few times and I haven't noticed one bit of difference in performance or gas mileage. Maybe I'm the lucky one and my car is just ambivalent, or maybe the little dance ritual I do before starting her up is the charm.

hi,
i have s600 2004. According to the manual, it requires 93 octane gas. I cant find it in los angeles. any advice?

Yes, the knock sensor will detect the knock and retard, but that means that the knock (and potentially the damage) has already occurred!

for supermike: You probably have 91 octane available. That is fine at your sea level altitude. Premium fuel varies in octane by altitude. Most deliveries of 93 octane are for higher altitude locations. In other words, 91 octane at sea level = 93 octane at say, Denver.

for all the rest of you: What is your problem? You bought a Benz and it likes premium fuel, so let the Big Dog drink. You can save a couple of dollars per fill-up and possibly pay a bigger price later.

If you cannot afford to put the proper fuel in the car, perhaps you should not be buying it..

Why would you need higher octane fuel at elevated altitude? The pressure in the cylinder is lower at higher altitudes, unless you have a supercharger to compensate. I think that you have it in reverse.

The problem with knock sensors retarding the spark is that this causes excessive heat at the exhaust valves. It is a very bad idea to detune a high-compression engine by delaying the spark. You could drop a valve.

you can absolutely run regular fuel in these things...no doubt about it..the computer is actually set for that possibility. That's why when you may 'chip' the computer you must absolutely use premium, it insists upon premium fuel whereas the stock chip expects you to probably/possibly not. It's programmed for potential thriftiness ...... actually throwing premium in an around town car is worthless....As to potentional engine damage..none...remember, the fuel concerns contribute to car manufactures in a political type of fashion....

who knows what the hell octane really is?

Octane is a measure of a fuels resistence to combust. IE a 93 octane will be harder to ignite than an 87. The higher the compression, the more combustion resistence you get.

Thats the only difference, labling higher octane fuel as "premium" is misleading, it isn't any better or worse than the other. All gas is required to have the minimum amount of cleaners in it etc.

What it really comes down to is, run what the manual calls for. If spending a few extra cents on 91 or 93 really makes that much of a difference in your budget you have no business buying a high end car.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200