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.

 

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.

 

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.

 

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.

 

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.

 

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?

 

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.

 

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.

 

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

 

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

 

I remember the Sunoco dial-a-grade:
sunoco-dial-grade-custom-blended_1_e0ca30fe5adb294f72864ce9d4460d54.jpg

Ha! I remember those as well. I think Dad always got 210 or 220.

 

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.

 

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.

 

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 gather than the problem of ethanol in gasoline for boaters was inboard (fiberglass/epoxy?) fuel tanks which were softened by the ethanol and then leaked. Is that correct? Presumably it is not the engine itself.

I wonder if ethanol-free gasoline works better than 10% ethanol in those aircraft engines (e.g., Rotax) designed for auto gasoline (called "mogas" as opposed to 100 LL avgas). ROTAX 912 914 fuel use operation | Sport Airplane Pilot Hub | Sport Aviation Center | Paul Hamilton (at http://airplanepilot.sportaviationcenter.com/light-sport-planes/maintenance-inspections/rotax-fuel/ )

What is the cost of ethanol-free gasoline compared to the 10% ethanol?

 

In addition to what Bob posted, the main issue with most recreational boat engines, is they average less than a month of actual running on an annual basis. It mostly has to do with storage. Gasoline can be become "stale" or "sour" over time. Ethanol is very corrosive and many older marine engines and their fuel systems (manufactured before 1990) simply were not designed with E10 in mind. As Bob posted there is the phase separation (If E10 is used) where the ethanol and water separate and form a layer on the bottom of the tank. This usually happens when the fuel sits for a while. The best advice has been to use E0 and when storing the boat for the winter, fill it 95% full (Allow for expansion) with E0 and add a stabilizer, then run the engine for a bit to get the stabilizer completely through the fuel system. Ethanol is known to attack the plastics and rubber in the older fuel systems. A full tank minimizes the formation of condensation (water). Yes, ethanol absorbs water but there is a limit of how much it can absorb. E15 is a definite no-no for marine engines. And yes, I've already observed one station in our region that has E15 available.

Ethanol And Older Engines - Seaworthy Magazine - BoatUS (at https://www.boatus.com/seaworthy/magazine/2012/april/ethanol-and-older-engines.asp )

Ethanol gasoline can pose problem for boat motors (at http://www.charlotteobserver.com/living/home-garden/article97604942.html )

Fishermen beware: ethanol fuel is deadly for outboard motors - AllOutdoor.com (at http://www.alloutdoor.com/2013/06/25/fishermen-beware-ethanol-fuel-deadly-outboard-motors/ )