What octane rating do you use?
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Senior Member
Joined: Nov 2016
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From: Western Massachusetts
2019 S450 Silver w/ black interior
What octane rating do you use?
I am asking specifically for the bi-turbo V-8 guys like me. I have put almost 6,000 miles on my E550 and today at the pump was the first time I saw the sticker on the fuel filler door that said minimum 91 octane fuel. All this time I have been using 93. When I had my Buick GN I always used the highest octane available at the time (Sunoco Ultra 94) with 5-8 gallons of VP 118 octane mixed in. I was also running 28-30 pounds of boost too. I can't imagine the boost being that high in my E550.
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
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From: MA
2008 E350 4Matic, 2011 E350 4matic
Every once in a while I mix in 1/3 tank of regular with 93 which would bring it down to 91. My E350 isn't a turbo though and I don't drive it that hard normally. Technically you should be fine regardless as all the west coast has is 91, no 93.
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From: Bradenton, FL
'12 E550 4M, '14 ML5504M
I was looking for a post I wrote some time ago on this, but this was the gist of it... Octane is an indirect measure of how fast fuel burns. If there is a minimum octane rating, it's because the engine was designed with a burn rate in mind, which is reflected in the timing of the engine, or the time it takes for the engine to extract all the energy from the burning fuel before the cylinder begins its trip back up to top dead center. Fuel burning faster than expected or uncontrolled burning of the fuel is called, "detonation", "ping" or, "knock", which is why octane ratings are also called anti knock ratings or similar.
If equipped, and I think our bi turbos are so equipped, an engine will change its timing to prevent detonation, which has the related effect of lowering its peak output. Unfortunately it doesn't work the other way; adding a higher octane fuel will not give more power, only ensure the engine can produce its peak output.
So using lower octane than 91 will not harm the w212, but it will not produce full power.
If equipped, and I think our bi turbos are so equipped, an engine will change its timing to prevent detonation, which has the related effect of lowering its peak output. Unfortunately it doesn't work the other way; adding a higher octane fuel will not give more power, only ensure the engine can produce its peak output.
So using lower octane than 91 will not harm the w212, but it will not produce full power.
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From: Idaho
2023 GLE 450
Mixing gas to get a certain octane is not as easy as 1/2 a tank of one added to another. I recently listened to a podcast wherein this was discussed specifically, I'll look for it and add a link. I can tell your for sure, trying to adjust your octane by mixing in this manner is not productive nor accurate.
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From: Vancouver B.C. Canada
2014 E550 4MATIC TUNED - Turbo Upgraded Stage 3
I am asking specifically for the bi-turbo V-8 guys like me. I have put almost 6,000 miles on my E550 and today at the pump was the first time I saw the sticker on the fuel filler door that said minimum 91 octane fuel. All this time I have been using 93. When I had my Buick GN I always used the highest octane available at the time (Sunoco Ultra 94) with 5-8 gallons of VP 118 octane mixed in. I was also running 28-30 pounds of boost too. I can't imagine the boost being that high in my E550.
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
I always go with highest octane level i can get from local stations.
In B.C. Canada, Chevron has 94 octane 0% ethanol.
But i have also heard our fuel quality is not as good compare to U.S.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
Mixing gas to get a certain octane is not as easy as 1/2 a tank of one added to another. I recently listened to a podcast wherein this was discussed specifically, I'll look for it and add a link. I can tell your for sure, trying to adjust your octane by mixing in this manner is not productive nor accurate.
Senior Member
Joined: Nov 2011
Posts: 308
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From: Houston TX
2015 E400
So as long as your engine doesn't knock, so there's no damage to your engine, the 50 cents per gal savings, currently $2.39 of 93 super vs $1.89 of 87 reg, a 26% savings.
So what's the % reduction of the reduced "performance" of not getting "full power" ?
Is it 26% less?
So what's the % reduction of the reduced "performance" of not getting "full power" ?
Is it 26% less?
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From: New Jersey
2010 E550 P2 w/AMG Sport Package + Pano, 2015 Nissan Pathfinder
I have only put 93 in my E550. My engine is N/A but I was always under the impression we had to use only Super (93 where I'm at).
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From: MA
2008 E350 4Matic, 2011 E350 4matic
As for 100 octane, wow, $7.37 a gallon.
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From: Idaho
2023 GLE 450
How do you think they get 89? They normally just have a super and regular delivery and they mix it to get an 89 mix, just a different ratio. Anyway, there used to be some guy on here who claimed he just ran 87 all the time and nothing bad ever happened. Even the manual says that if they don't have super, you can use regular, just don't give it full throttle and to get super as soon as possible.
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None
I was looking for a post I wrote some time ago on this, but this was the gist of it... Octane is an indirect measure of how fast fuel burns. If there is a minimum octane rating, it's because the engine was designed with a burn rate in mind, which is reflected in the timing of the engine, or the time it takes for the engine to extract all the energy from the burning fuel before the cylinder begins its trip back up to top dead center. Fuel burning faster than expected or uncontrolled burning of the fuel is called, "detonation", "ping" or, "knock", which is why octane ratings are also called anti knock ratings or similar.
If equipped, and I think our bi turbos are so equipped, an engine will change its timing to prevent detonation, which has the related effect of lowering its peak output. Unfortunately it doesn't work the other way; adding a higher octane fuel will not give more power, only ensure the engine can produce its peak output.
So using lower octane than 91 will not harm the w212, but it will not produce full power.
If equipped, and I think our bi turbos are so equipped, an engine will change its timing to prevent detonation, which has the related effect of lowering its peak output. Unfortunately it doesn't work the other way; adding a higher octane fuel will not give more power, only ensure the engine can produce its peak output.
So using lower octane than 91 will not harm the w212, but it will not produce full power.
Octane is not a measure of fuel burn rate. Diesel fuel has a specification for cetane, which is actually a measure of burn rate - but this is not applicable to gasoline.
Octane is a measure of resistance to pre-detonation. If you use an octane rating too low for your engine, the air/fuel mixture explodes before it should (due to compression & heat), which causes knock.
You are correct - all modern engines have knock sensors, and will adjust timing to cool the cylinder temperatures and prevent knock.
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I am asking specifically for the bi-turbo V-8 guys like me. I have put almost 6,000 miles on my E550 and today at the pump was the first time I saw the sticker on the fuel filler door that said minimum 91 octane fuel. All this time I have been using 93. When I had my Buick GN I always used the highest octane available at the time (Sunoco Ultra 94) with 5-8 gallons of VP 118 octane mixed in. I was also running 28-30 pounds of boost too. I can't imagine the boost being that high in my E550.
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
So am I going overboard with 93? Can I safely drop down to 92 or 91, or just stick with what I am using?
Member
Joined: Apr 2011
Posts: 99
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From: Bradenton, FL
'12 E550 4M, '14 ML5504M
George, your description of octane is completely wrong, but your conclusions are still correct.
Octane is not a measure of fuel burn rate. Diesel fuel has a specification for cetane, which is actually a measure of burn rate - but this is not applicable to gasoline.
Octane is a measure of resistance to pre-detonation. If you use an octane rating too low for your engine, the air/fuel mixture explodes before it should (due to compression & heat), which causes knock.
You are correct - all modern engines have knock sensors, and will adjust timing to cool the cylinder temperatures and prevent knock.
Octane is not a measure of fuel burn rate. Diesel fuel has a specification for cetane, which is actually a measure of burn rate - but this is not applicable to gasoline.
Octane is a measure of resistance to pre-detonation. If you use an octane rating too low for your engine, the air/fuel mixture explodes before it should (due to compression & heat), which causes knock.
You are correct - all modern engines have knock sensors, and will adjust timing to cool the cylinder temperatures and prevent knock.
Member
Joined: Nov 2015
Posts: 206
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From: Southern
2014 E-350
How do you think they get 89? They normally just have a super and regular delivery and they mix it to get an 89 mix, just a different ratio. Anyway, there used to be some guy on here who claimed he just ran 87 all the time and nothing bad ever happened. Even the manual says that if they don't have super, you can use regular, just don't give it full throttle and to get super as soon as possible.
In fact, at the terminal there is only Premium and Regular. For the retailers who have a mid-grade tank, the tanker takes on the correct amount of Premium and Regular in order to deliver the mid-grade. Some terminals may have mid-grade as an available pick-up, but it is mixed at the rack via a proportioner prior to going in the truck.
But most retailers these days have a tank for Premium, a tank for Regular, and a Diesel tank where applicable. Mid-grade is mixed at the retailer in these cases.
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From: New Jersey
2010 E550 P2 w/AMG Sport Package + Pano, 2015 Nissan Pathfinder
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