Anyone switched to 87 octane?

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Wild one

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I'll go ahead and throw in my $0.005 worth on the topic.
The first thing I will say is that I worked for 12 years as an automotive test engineer specializing in fuel economy testing. Manufacturers of complete vehicles down to some crazy "as seen on TV" aerodynamic bolt on or snake oil would hire our company to perform industry certified fuel economy testing. There are several industry standards from enclosed dyno cell cycles to over the road testing based on the SAE recommended practices. I am in no way trying to say I'm the foremost expert in fuel economy testing, nor trying to say anybody else posting about this is wrong. However I will say that nobody I have ever seen on one of these posts is even close to performing what would be considered a certified or industry recognized fuel economy test. Again, not saying anybody is wrong and they can draw their own conclusions on what they have done and make decisions based on what they have done but no manufacturer, big investor, etc... who use that data to make a business decision.
I have a '16 Power Wagon with the 6.4 and have done a couple of "studies" between 87 and 89 octane. Always ran at least 3-4 tanks of either octane in a row. Have never noticed any "seat of the pants" power or performance difference, and there was no obvious fuel economy difference that I could tell....at least not obvious enough to justify spending the extra money for 89 octane. Yes, I agree with previous posts saying that the ECM may be pulling timing out of the engine with the lower octane which would lead to reduced power....you don't know unless you are monitoring the data. But keep in mind you are rarely ever using the full power of the engine. The horsepower rating of the engine is the maximum power it can achieve, and not what you are using the vast majority of the time. It doesn't matter that the engine is rated at 410 HP because it doesn't take anywhere close to the much power to cruise down the freeway at 70 mph.
But hey, if people want to spend their money on 89 octane I don't have any problem with it.
The 6.4 truck has a lower compression ratio,then the 5.7's do. 6.4's are 10:1 , 5.7's are 10.5:1. The 6.4 in the HD trucks is designed to run wide open for 12 minutes at full load on 87. Not saying your post is wrong or anything,just pointing out one of the reasons why you don't notice any differance between 87 and 89 in your 6.4 HD truck
 
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MateoQueFeo

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Would there be any advantage to using higher octane based on driving elevation (i.e. mountainous terrain)?
 

Wild one

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Would there be any advantage to using higher octane based on driving elevation (i.e. mountainous terrain)?
Nope. Less barometric pressure and oxygen at higher altitudes,means there's less cylinder filling of oxygen and fuel,consequently when the air / fuel mix is compressed,there's less cylinder pressure,and the requirement for high octane fuel decreases. If anything high octane fuel with stock timing at higher altitudes,would decrease your power output with its slower burn
 

Docwagon1776

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Would there be any advantage to using higher octane based on driving elevation (i.e. mountainous terrain)?

Like Wild One said, the opposite. I'll add especially for naturally aspirated. And you'll be down on power due to the lessened air charge. Forced induction, being less reliant on atmospheric pressure, largely addresses this issue and is one place turbos really shine.
 

Awokenotwoke

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The manual for my 2022 1500 5.7 says: “This engine is designed to meet all emissions regs and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having an octane range 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended.”

Can anyone describe what the (R+M)/2 method is; and what is “Plus” for gasoline?
I have never seen these ratings at the fuel pumps even though I use 87 gasoline from Tier 1 retailers.
 

ramffml

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The manual for my 2022 1500 5.7 says: “This engine is designed to meet all emissions regs and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having an octane range 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended.”

Can anyone describe what the (R+M)/2 method is; and what is “Plus” for gasoline?
I have never seen these ratings at the fuel pumps even though I use 87 gasoline from Tier 1 retailers.

"Plus" is marketing BS, ignore it. What matters is octane number (87, 89) and what elevation you're at. If you're in Boulder CO you can run 85 when your manual says 87. Otherwise always follow the number which for us hemis is 87 minimum.
 

Docwagon1776

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The manual for my 2022 1500 5.7 says: “This engine is designed to meet all emissions regs and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having an octane range 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended.”

Can anyone describe what the (R+M)/2 method is; and what is “Plus” for gasoline?
I have never seen these ratings at the fuel pumps even though I use 87 gasoline from Tier 1 retailers.

Short answer: It's the standard way octane is calculated. Almost all pumps have that formula in small type above the bigger octane number, but it's irrelevant to you except for curiosity sake because you are only getting the final answer to the math problem, which is the big number you see on the button or handle. "Plus" is just a marketing label. In different countries, and even at different elevations, "Plus" may refer to a different octane but 89 octane is always 89 octane, regardless.

The longer answer is M stands for "motor octane rating" and is how resistant to spontaneous combustion the fuel is at higher temperatures and heavier loads. The R stands for "research octane rating" and is the same measurement for lower temperatures at lighter loads. Adding them together and then dividing by 2 gives you the average of those two numbers. That average is the octane rating you see on the pump handle or button.
 

Fatbob Frank

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I don't even know of a station that sells 93 in Iowa!
The dragstrip in Earlville might offer it...
 

Daw14

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Ive been using 87 since inception. You funny bunnies down there are complaining about $5/gallon. Here in the north, we're paying 2.10/L which translate to almost 8bucks a gallon.
I feel much better running 93 ,now I know what you guys are paying .
 

Justin33

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try this fuel cleaner, and as a bonus you can see how it will clean piston tops, this was Coreys truck one treatment... 3 vehicles same result..

top of piston, hard to find anything that will clean like this..

View attachment 493406


  • Cleans injectors, carburetors, valve and combustion chamber deposits with a concentrated blend of the most powerful high-temp and low-temp detergents available
  • Cleans all forms of fuel injectors, including GDI
  • Enhances fuel stability; reduces gum and varnish formation
  • Use one bottle per tank for most effective treatment, cleans to nearly 100% efficiency in one treatment
  • Reduces need for octane by up to two points
  • Contains synthetic upper cylinder lubricant
  • Cleans pollution control valves
  • Suitable for use with oxygenated fuel
  • Safe for continual use
  • Same chemistry is also available in 4oz dosage as Complete Fuel System Cleaner - Powersports
My truck only has 30k and is a 15. What would I gain by doing this?
 

Burla

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look at the picture, continual use will keep piston rings clean, stop one of the things that ages engines and creates blowby.
 

IdahoDen

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I'll go ahead and throw in my $0.005 worth on the topic.
The first thing I will say is that I worked for 12 years as an automotive test engineer specializing in fuel economy testing. Manufacturers of complete vehicles down to some crazy "as seen on TV" aerodynamic bolt on or snake oil would hire our company to perform industry certified fuel economy testing. There are several industry standards from enclosed dyno cell cycles to over the road testing based on the SAE recommended practices. I am in no way trying to say I'm the foremost expert in fuel economy testing, nor trying to say anybody else posting about this is wrong. However I will say that nobody I have ever seen on one of these posts is even close to performing what would be considered a certified or industry recognized fuel economy test. Again, not saying anybody is wrong and they can draw their own conclusions on what they have done and make decisions based on what they have done but no manufacturer, big investor, etc... who use that data to make a business decision.
I have a '16 Power Wagon with the 6.4 and have done a couple of "studies" between 87 and 89 octane. Always ran at least 3-4 tanks of either octane in a row. Have never noticed any "seat of the pants" power or performance difference, and there was no obvious fuel economy difference that I could tell....at least not obvious enough to justify spending the extra money for 89 octane. Yes, I agree with previous posts saying that the ECM may be pulling timing out of the engine with the lower octane which would lead to reduced power....you don't know unless you are monitoring the data. But keep in mind you are rarely ever using the full power of the engine. The horsepower rating of the engine is the maximum power it can achieve, and not what you are using the vast majority of the time. It doesn't matter that the engine is rated at 410 HP because it doesn't take anywhere close to the much power to cruise down the freeway at 70 mph.
But hey, if people want to spend their money on 89 octane I don't have any problem with it.
We live at 6200 ft elevation, so all of reg gas out here is 85 octane, mid is 87 and premium is 91. I ran my 2014 1500 Longhorn 5.7L on 85 octane for 7 years and the performance was just fine.
 
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