Octane, ethanol
Thread Starter
Member
Joined: Apr 2011
Posts: 111
Likes: 0
From: North Carolina
2012 C350 Sport - Iridium Silver w/Ash
Octane, ethanol
Just found out that nearly every station in NC has 10% or more ethanol. 
I have one station not too far from my house. It offers one pump w/o ethanol gas. Just got a new C350 and it says use 91 or greater octane. The station offers only non-ethanol BP silver with 89 octane. Which one to go with? Put in the silver this morning. I figure it's better than 93 Octane with 10% ethanol.
You can check your state - at least five or ten states don't require any labeling. NC's labeling law expired in 2009. They passed a new law to require it but it's dragging slowly because of various outside-their-control factors.
http://pure-gas.org/
http://pure-gas.org/extensions/map.html
I have one station not too far from my house. It offers one pump w/o ethanol gas. Just got a new C350 and it says use 91 or greater octane. The station offers only non-ethanol BP silver with 89 octane. Which one to go with? Put in the silver this morning. I figure it's better than 93 Octane with 10% ethanol.
You can check your state - at least five or ten states don't require any labeling. NC's labeling law expired in 2009. They passed a new law to require it but it's dragging slowly because of various outside-their-control factors.
http://pure-gas.org/
http://pure-gas.org/extensions/map.html
MBWorld Fanatic!
Joined: Oct 2009
Posts: 2,286
Likes: 62
From: eNyCe
Steel Grey Metallic C63!!
You have nothing to worry about. MB engines are designed to be able to run on 10% ethanol. All gas stations in NY and NJ have at that 10% ethanol in the gas. It does not lower your octane rating.
Ethanol will reduce your mpg rating as ethanol has less energy content vs. gasoline.
Ethanol will reduce your mpg rating as ethanol has less energy content vs. gasoline.
MBWorld Fanatic!
Joined: Feb 2004
Posts: 3,986
Likes: 6
From: SEATTLE WASHINGTON USA
'08 C300 Lux Barolo Red Beige Leather P2 MM 18" wheels '84 944
You have nothing to worry about. MB engines are designed to be able to run on 10% ethanol. All gas stations in NY and NJ have at that 10% ethanol in the gas. It does not lower your octane rating.
Ethanol will reduce your mpg rating as ethanol has less energy content vs. gasoline.
Ethanol will reduce your mpg rating as ethanol has less energy content vs. gasoline.
Member
Joined: Aug 2011
Posts: 107
Likes: 0
2011 C300 4matic sport
Ditto nothing to worry about. Ethanol actually has a higher octane rating but lower energy density, but it will not hurt the engine at 10%. My C300 is even allowed to run on E85 but I'll never put that in my tank.
Super Moderator
Joined: Jun 2008
Posts: 19,942
Likes: 192
From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
You should use the higher octane fuel. The car is designed & adequately mapped to run on it. Modern materials & lubricants will ensure no wear issues. While the ECU has a very conservative map that would allow running the lower octane fuel (can be altered with Star) it would mean that the engine was frequently running with retarded timing.
The energy value of the alcohol portion of the blend is lower than the petroleum fraction which has a slightly adverse effect on fuel consumption. The counter to this is that running retarded every time the knock sensor detects the onset of knock on the lower octane fuel will also be detrimental to consumption. The slight differences would require some very sophisticated dynamometer testing to quantify.
The energy value of the alcohol portion of the blend is lower than the petroleum fraction which has a slightly adverse effect on fuel consumption. The counter to this is that running retarded every time the knock sensor detects the onset of knock on the lower octane fuel will also be detrimental to consumption. The slight differences would require some very sophisticated dynamometer testing to quantify.
Junior Member
Joined: Jun 2010
Posts: 56
Likes: 0
From: DC Metro Area
08 C350 Sport
My car was running really bad with Synoco, was down on power. Now I swithced to Shell and what a difference, like adding more HP completely different. Both have 10% ethanlol, NVA area does not have gas stations with no ethanol.
Super Member
Joined: Jan 2011
Posts: 534
Likes: 1
From: NJ
2008 C350 Sport
Your sig says "M3 Couple"...do you have more than one or is it a "Coupe" ? ha.
Trending Topics
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
MBWorld Fanatic!
Joined: Jul 2008
Posts: 8,384
Likes: 800
2019 G70 6MT & 2022 Ford Maverick XL
Actually, I found a station close to my house selling 0% ethanol gasoline at 90 octane. I'm gonna try it. I've ran 87 in my 05 C230 numerous times with no noticeable loss in performance or economy.
