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I have a 2017 RAM 1500 with the 5.7. My book say 87 octane gas is acceptable, but 89 octane gas is recommended.

Hers is my question does 89 octane make any difference at all? Does it give any better significant miles per gallon?
 

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Maybe slightly better MPG and performance with 89. You might want to compare averages. You may not feel much of any difference. Cost-wise and depending on your daily driving habits, you may be fine with 87 regular.
I did not notice a significant difference.
 

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If Chrysler recommends 89, it means they ran their tests with it. So it either burns slightly cleaner or gets slightly better gas mileage in the tests. Probably just a little more power as it may allow a little more timing advance before the knock retards timing.. I would not expect big changes between 87 and 89.
 

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Virginia Gentleman
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I have a 2017 RAM 1500 with the 5.7. My book say 87 octane gas is acceptable, but 89 octane gas is recommended.

Hers is my question does 89 octane make any difference at all? Does it give any better significant miles per gallon?
I have a 2006 Ram 1500 w/Hemi. My book says the same. At first I used 89 octane all the time. Then I began to experiment using 87 octane. I cannot tell the difference using my seat-of-the-pants meter. I kept a fuel log for the first 7 years. Never did see a significant difference. I use 87 octane almost exclusively now. 89 octane is 30 cents/gallon higher. I only use 89 octane when I am towing or hauling heavy loads. As I understand it the Hemi has a knock sensor and the timing is retarded when 87 octane is used. There is probably slight hp reduction, but it's not noticeable to me.
 

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Mid-grade can cost from 15 to 30 cents more per gallon than regular, depending on the gas station. Your performance will be better with mid-grade, but as IC said, how you use your truck makes a difference. For regular in-town driving, 87 octane should be fine, but for driving up hills with a load at freeway speeds, 89 octane is preferable. One option is an octane booster. Dollar Tree sells a container of it for $1, which will be cheaper than filling up with 89 octane.
 

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Around here, 10% ethanol adds 1 point to the octane. From 87 to 88.
This makes sense as alcohol burns slower. That is the main anti-ping property of higher octane for higher compression engines.
 

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Interesting. Around here E10 is rated 87 octane.

There is one station, Murphy's Express, that has non-ethanol fuel rated at 87 octane.
 

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The recommendation is the same for my 2007 Ram. I have found very little difference with 89 octane vs 87. In the futire, I will only use 89 when towing. I can mix my own by combining 87 octane E10 with 91 or 93 non-ethanol.
 
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The myths about premium / higher octane gasoline giving better performance and better fuel economy have persisted for years. Go to this link and it shows that the energy content of higher octane gasoline is lower than 87 octane fuel.

Energy content of fuels - Appropedia: The sustainability wiki (at http://www.appropedia.org/Energy_content_of_fuels )

Look at this reference article that lists energy content of various fuels. Straight 87 octane gasoline has 125,000 BTU per gallon. Gasohol (10% ethanol) has 120,900 BTU. High octane aviation gasoline has 120,200 BTU. All are close but this dispels the theory that higher octane provides more performance and better fuel economy.

Notice that diesel fuel has higher energy content / density. Diesel engines have a reputation for higher fuel efficiency / lower fuel consumption versus gasoline. But all of the lower fuel consumption in a diesel engine is not due to the fuel alone. A higher compression ratio and direct injection lead to these efficiency gains along with the fuel.

Now you can encounter the situation where an automobile engine has a knock sensor installed on the engine block. If detonation / pinging is encountered with lower octane fuel, the engine management software will retard the ignition timing slightly to prevent detonation. Retarding the timing event will cause slightly reduced performance and slightly higher fuel consumption. So if you use higher octane gasoline there is no detonation and no spark timing retard and the engine performs as designed for better performance and slightly better fuel efficiency. This is mistakenly attributed to better fuel but it is an indirect result
 

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Virginia Gentleman
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I can mix my own by combining 87 octane E10 with 91 or 93 non-ethanol.
If you purchase mid-grade (89 octane) fuel at the local Sheetz, that's precisely what the pump does. They have two tanks with 87 octane, one tank with 93 octane and a third tank with diesel. To get the 89 octane the fuel is pumped from the 87 and 93 tanks. They don't have a tank that is 89 octane.
 

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Interesting. Around here E10 is rated 87 octane.

There is one station, Murphy's Express, that has non-ethanol fuel rated at 87 octane.
I was under the impression that all octane grades of retail auto fuel contained ethanol up to 10% (except for the few outlets selling non-ethanol gasoline). Are you saying that only AKI 87 contains ethanol?
 

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If you purchase mid-grade (89 octane) fuel at the local Sheetz, that's precisely what the pump does. They have two tanks with 87 octane, one tank with 93 octane and a third tank with diesel. To get the 89 octane the fuel is pumped from the 87 and 93 tanks. They don't have a tank that is 89 octane.
Does the 93 octane gasoline contain ethanol at 10%?

I remember decades ago, maybe in the Midwest, seeing pumps that allowed consumer selection of octane in a range. This could only be accomplished if the pumped gas was blended from two fuels at the ends of the range.

The engine in my wife's 2007 Volvo XC90 is the Volvo-Ford 3.2L short inline-6 which has a compression ratio of about 11:1. The manual says it will run without damage on 87 AKI, but needs 91 AKI for "optimum" performance. I mix equal parts of 89 and 93, but she just puts in 93. Doesn't the "premium" 93 also have more fuel injector cleaning additive than the lower octane grades?

I see some risk in habitually challenging the knock sensor to do its job. Inside a Car - Knock Sensors (at https://www.azosensors.com/article.aspx?ArticleID=50 )
 

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I was under the impression that all octane grades of retail auto fuel contained ethanol up to 10% (except for the few outlets selling non-ethanol gasoline). Are you saying that only AKI 87 contains ethanol?
It depends on the retailer. Most have ethanol in all fuel grades.
 

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Does the 93 octane gasoline contain ethanol at 10%?
This station (actually a convenience store) probably has 10% ethanol in the 93 octane though I can't say for sure. There's is no signage indicating it is 100% gasoline - just signs stating the fuel may contain up to 10% ethanol.

Doesn't the "premium" 93 also have more fuel injector cleaning additive than the lower octane grades?
It depends on the retailer. It's not a given that the higher octane has more additives.
 

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Different state laws about oxygenated fuels may decide what additives go in it. Ethanol has been deemed safe. NY banned MTBE as it is a carcinogen that was entering the ground water.
http://ethanolrfa.3cdn.net/bb928477e5a5d04852_7ym6b9glg.pdf
MTBE controversy - Wikipedia (at https://en.wikipedia.org/wiki/MTBE_controversy )
I drove across the country recently and experienced the variability of gasoline quality and prices on the trip.
I remember the Sunoco dial-a-grade:
sunoco-dial-grade-custom-blended_1_e0ca30fe5adb294f72864ce9d4460d54.jpg
 

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They were in the '60's into the early-'70's?
Sunoco 260 was the 104 octane super-premium fuel. Like aviation grade.
Everything was tetra-ethyl lead back then to increase octane numbers and lube the exhaust valve seats. We were seeing increased lead levels in the environment.
Tetraethyllead - Wikipedia (at https://en.wikipedia.org/wiki/Tetraethyllead )
The gas pumps also had spinner wheels on the gallon/cost counter read-out panel that would spin and twirl and ding a bell while you were gassing up your ride to indicate fuel flow. They were fun to watch when I was a kid and dad was paying for it anyways. :cool:
 

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What era was that? It's cool!
I remember when I was a kid it was 3 pumps: regular, unleaded and premium. And it was full service with windshield clean and check oil and fluids. Good times.
Like Imperial noted it was back in the '60's and early '70's. When unleaded fuel became mandatory, those pumps disappeared. Eventually full service went away as well, except in NJ and OR.
 

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There are a number of gas stations in my area that sell no-ethanol premium (91 or 93 octane) mainly to cater to boaters. So if I mix 87 E10 with 91 no-ethanol 50/50, I get 89 octane with 5% ethanol. At these stations, the mid -grade is labeled as up to 10% ethanol so I don't think they are mixing at the pump.

I should add that the DIY mix can be cheaper than midgrade directly from the pump. If not, I don't bother.
 
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