Octane values for GLC43 AMG
Thread Starter
Junior Member
Joined: Nov 2024
Posts: 72
Likes: 12
Octane values for GLC43 AMG
This is not only my first Mercedes, but also my first vehicle with a turbo (and this one has 2...go figure)
I'd always heard that high compression need high octane.
The gas door says 91. I'm in the USA so I'm assuming that this is 91 octane as measured in the USA, not Europe. Right?
So when I pull up to a pump and they offer 89, 91 and 93, 91 is fine...or am I overthinking this?
Ed
I'd always heard that high compression need high octane.
The gas door says 91. I'm in the USA so I'm assuming that this is 91 octane as measured in the USA, not Europe. Right?
So when I pull up to a pump and they offer 89, 91 and 93, 91 is fine...or am I overthinking this?
Ed
Out Of Control!!
Joined: Nov 2018
Posts: 11,432
Likes: 5,343
From: San Francisco Bay Area
2019 C63CS
Correct, 91 AKI. You are overthinking it. The US spec engines are tuned for 91 AKI. EU spec engines are tuned for 98 RON. Europe only measures RON. RON is determined by testing the fuel at a low engine speed and temperature. The USA determines MON in addition to RON. MON is determined by testing the fuel under more stressful conditions. Then they calculate the Anit-Knock Index (AKI), which is the average of MON and RON, (RON + MON) / 2. It gives a better measure of how the fuel holds up under stress. With Europe only measuring RON, one doesn't actually know how good the fuel is under stress. Also, higher octane is not automatically better as that makes the fuel harder to combust. The octane rating goes hand in hand with the engine tune. Putting in 93 AKI instead of 91 AKI is not gonna make the engine produce more power, unless you have an aftermarket tune with a 93 map that takes advantage of it.
Last edited by superswiss; Nov 22, 2024 at 08:05 PM.
Thread Starter
Junior Member
Joined: Nov 2024
Posts: 72
Likes: 12
Wow...that's a lot of technical jargon. Thanks! Its difficult to find 91 octane fuel. Not all gas stations have it...although I've read that 91 octane is just the 89 and 93 being blended together at the pump...I get gas at Costco and they only carry 89 and 93...fortunately, the 93 isn't all that expensive.
Out Of Control!!
Joined: Nov 2018
Posts: 11,432
Likes: 5,343
From: San Francisco Bay Area
2019 C63CS
Wow...that's a lot of technical jargon. Thanks! Its difficult to find 91 octane fuel. Not all gas stations have it...although I've read that 91 octane is just the 89 and 93 being blended together at the pump...I get gas at Costco and they only carry 89 and 93...fortunately, the 93 isn't all that expensive.
https://www.toptiergas.com/
