91 vs 94 octane
MBWorld Fanatic!
Joined: Oct 2014
Posts: 4,524
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From: WI
17 E43; 21 GLS580
Might wake up a few additional ponies but nothing you would notice while driving. The main reason for premium in these engines is to avoid predetonation due to their high compression virtually all turbo engines require premium gas.
Super Member
Joined: Nov 2017
Posts: 669
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From: Hermosa Beach, California
2018 E400 Coupe
Google "does higher octane gas increase horsepower" and you'll see that the idea that higher octane will increase a car's performance is largely a myth based on a fundamental misunderstanding of what "octane" means. As stated by one reliable source, "[Higher] octane does not offer any better fuel mileage, increase engine horsepower, or make the engine start quicker.... Because higher octane gas burns slower, it is more resistant to knock when subjected to higher RPM and cylinder pressures. Compression ratios also factor into cylinder pressures." That is, the higher the octane, the more it can be compressed before it spontaneously combusts, and that's why the higher the engine's compression ratio, the higher the octane it requires to run smoothly and efficiently. If the fuel combust prematurely, you lose power and hear the knock or ping. You therefore can safety use the lowest octane gas that your car will run on without knocking or pinging, or you can pay more to make yourself feel good. Just be sure to buy quality fuel, such as any Top Tier brand (which has to do primarily with the type and amount of detergent added to the gas), and avoid old, rundown stations that are likely to have rusty old underground tanks that are badly contaminated with dirt and water.
Last edited by The_Judge; Nov 5, 2017 at 08:26 PM.
