E15 gas in our C63s
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Newbie
Joined: Jun 2016
Posts: 13
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From: Seattle
2014 C63
E15 gas in our C63s
Does anybody know the impact 15% ethanol gasoline could have on our motors long term? I don't plan on getting rid of my 2014 any time soon.
Biden will allow summer sale of E15 gas - NPR
Biden will allow summer sale of E15 gas - NPR
Member
Joined: Jan 2020
Posts: 129
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E63
Having 15% is no problem. Manufacturers have been tuning cars for 15% for a long time now. These days it's very uncommon to find stations that don't have some E in the fuel. The swing from summer to winter is generally 5-15%, so you've been using it all along 
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2012 C63;1971 280SE 3.5(Sold);2023 EQS 450 SUV 4 Matic (Wife's)
The owner's manual says unleaded fuel with additives can be used. However, the concentration of additives in he fuel, of which ethanol is one, must be less than 10%.
Member
Joined: Aug 2012
Posts: 194
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C63 P31, C320
A lot of members including myself are running full e85 with a flex fuel kit. 15% is nothing considered 91 is already around 10%. Usually summer gas blends tend to have more ethanol. Just paying more for less gas
Senior Member
Joined: Jan 2018
Posts: 415
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From: Whitehouse Station, NJ
2012 C63 P31 Sedan
There seems to be some anecdotal evidence of ethanol being corrosive to magnesium alloys. With the documented cases of deteriorated intake manifold components on the M156, I would proceed with caution, or at least budget having to replace those components. I believe there are aftermarket companies that make aluminum replacements for these components.
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Joined: Jun 2008
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From: Los Angeles
2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
Agree. Ethanol will make magnesium into Swiss cheese. I don’t think 15% will do anything considering that winter gas can have up to 10%, but proceed with caution anyway.
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2007 Mercedes E63 AMG
our computers and fuel system will have no issue with E15 blend gasoline besides reduced MPG. beyond 15%, the computer's default tune will not be mapped correctly to make the best use of the additional ethanol which will further reduce power and MPG.
Thread Starter
Newbie
Joined: Jun 2016
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From: Seattle
2014 C63
Just FYI. This seems to be a reliable source for non-ethanol gas if anyone else has concerns: https://www.pure-gas.org/extensions/maps.jsp
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Joined: Apr 2022
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W211 E63 AMG
most of the gains are through the cooling effect of ethanol if you don't have a tune specifically for what fuel you are running. adding octane to a tune that isn't configured for that octane will actually cause you to lose power.
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Joined: Oct 2007
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From: Texas
10 C six trizzle
the addition of 15% ethanol netting 93 octane will offer improved performance. It will net the same if not worse than 93 octane with 10% ethanol. They are basically using 90% of 85 octane and blend in the ethanol around 106 octane to get the cocktail to hit 93. So now we'll be starting with even crappier fuel like 80 octane lol. this is a huge loss. I'd recommend more frequent oil changes as ethanol breaks oil down quicker.
