Jeep Commander Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
72 Posts
Discussion Starter #1 (Edited)
Does the grade of gas make a difference in a 4.7 Commander? I never really learned what the difference is in general.

Also, does anything higher than 87 even work in the 4.7 flex fuel commander?
 

·
Registered
Joined
·
389 Posts
It should say what is recommended or required in the manual. Going off what I know of the HEMI in the Chrysler Aspen, it is recommended to use 89 octane in it (midgrade). However, it also says, if no problems are present when using 87 (regular), you can use it as well.

I'd guess that the 4.7 recommends 87 octane as it is not a high performance engine. Using a higher octane gas will not produce better affects in this case, and can actually create worse gas mileage if it doesn't ignite sometimes due to the higher octane.

As I said, I am pretty sure the 4.7 uses 87, however you need to check your manual or let another 4.7 owner chime in.
 

·
Registered
Joined
·
63 Posts
Yeah I tried E85 in my 4.7. Like many others the mpg loss was too great to bother with. There's really no point to using E85 unless it's at least 50 cents cheaper per gallon than regular 87 octane. My 4.7 runs just fine on 87. I usually get 14 mpg city/highway driving.
 

·
Registered
Joined
·
5,598 Posts
i have used 87 as long as I have owned the commander.
I have had a couple times when it didnt run well, but that was
the retailer. Some retail gas stations have really poor quality
fuel.

I have used E85 a couple times but like everyone else said,
you spend more in fuel to spend less for it.
 

·
Registered
Joined
·
3,037 Posts
The Octane is just an "Anti-Knock" Rating, its the burning properties of the fuel. It has nothing to do with the amount of energy contained in the fuel, they all contain the same amount of energy. To get a higher Octane rating requires more expensive ingredients that is why it costs more, and the names "Premium" and "Mid-Grade" just mean the price.

High Performance Engines may push the envelop so hard and require the higher octane fuel, because lower octane fuel will detonate to early under the pressure and heat, i.e. cause knock. People incorrectly make the link that high octane fuel will somehow make more power, it doesn't.

In fact, higher octane fuel often has different vapor pressures and atomization of the fuel. You use higher than recommended octane, it could make it harder to cold start the motor and run worse in cold weather with a cold motor, and even lower the mileage. It will vary from motor to motor.

A few people have found they have gotten a little better mileage going to a little higher octane, and its usually the motors that state they can run on 87 but you get better performance on 89 octane.

Alcohol, which E85 is 85% ethanol alcohol, does contain less energy per volume then gasoline. So, if you use it, you will need to burn more to do the same amount of work or produce the same amount of energy, i.e. your mileage will go down. That is why everyone is telling you NOT to use it unless it is a lot cheaper then gas, because you will need to buy more to go the same distance.

My Commander is NOT Flex Fuel, but my '02 Caravan is, and its owner manual states you should use a special oil from the dealer if your going to use E85. I'd check your owner's manual and make sure your Commander does NOT have the same recommendation.
 

·
Registered
Joined
·
3,037 Posts
i use the 91 octane tune on my flashpac and run 91 most of the time its made a big difference in my 4.7
Just so you don't confuse some that don't know any better, the flashpaq retunes the engine to make more power, and it does that "pushing the envelop harder" making more pressure and higher temps in the cylinder that require more anti-knock rating from the fuel, that I talked about in my earlier post.

A stock 4.7L shouldn't see any benefit from switching to 91 octane.

I've seen posts of some claiming to get better mileage with 89 octane then using 87 octane, but I suspect those are the commanders that state, they can run on 87 octane but 89 octane will provide the best performance (is that the 4.7L or Hemi, or both?).

In that case, the motor is designed to run on 89 octane, but has a feature to detune itself if you put in 87 octane (I think it works off resonses from the knock sensor). And that detuning actually dropped your mileage a bit, so putting in 89 octane actually got you better mileage as well as more HP. At least that is the way my Chrysler 2.0L DOHC worked. It also depended on conditions, like cold weather, or high altitude, using the 87 octane gave just as good performance/mileage as the higher recommended octane.

I've tried on my 3.7L V6 Commander, and 89 Octane made such a little difference in highway mileage than 87 Octane, it didn't prove it just wasn't a normal variance between drives, definitely NOT worth the higher cost of the 89 Octane.
 

·
Registered
Joined
·
47 Posts
I have a HEMI and the manual states they do not recommend premium and 89 is recommended.

For the V6 and 4.7 models 87 is recommended.

I also recommend sticking with top tier gas stations like Shell, Exxon, and Mobil. I've had a significant drop in fuel economy with cheaper gas brands.
 

·
Registered
Joined
·
3,037 Posts
I have a HEMI and the manual states they do not recommend premium and 89 is recommended.

For the V6 and 4.7 models 87 is recommended.

I also recommend sticking with top tier gas stations like Shell, Exxon, and Mobil. I've had a significant drop in fuel economy with cheaper gas brands.
What Model Year is your Commander? Cause it may have changed from year to year. BUT, totally agree with the point, check the owners manual and use what is recommended.

Gasohol or E10, even E15 should lower you mileage a bit. If the pump is labeled to contain ethanol and this will vary from state to state, but in Maryland, it 'seems' they are no longer required to post on the pump if there is ethanol in the gasoline. It seems when I fill up I have no idea if there is ethanol in the gas anymore. There is also the oxygenation additives as well, that will lower mileage.

Maybe lower quality gas uses more of those additives and/or ethanol?
 

·
Registered
Joined
·
1 Posts
Does the grade of gas make a difference in a 4.7 Commander? I never really learned what the difference is in general.

Also, does anything higher than 87 even work in the 4.7 flex fuel commander?
Use what the owners manual states. Typically 87 unless otherwise stated
 

·
Administrator
Joined
·
15,513 Posts
40663
 

·
Registered
Joined
·
4 Posts
I feel like premium gasoline is just really for sports and we are just attracted by ads that is why we feel like we need to.
 
1 - 13 of 13 Posts
Top