89 octane recommend, does it really make a difference?

[grimreefer]

With the rate of delivery to most stations, the age of the fuel is not a concern I have. Water and/or sediment in the fuel is a much more prevalent issue which is one of the reasons I try to fuel from the same, known filling station. When traveling, I look for facilities that appear to be well maintained.

ETA: There's about a 36 cents/gallon difference between 87 and 89 octane in my area.

 

[RAM Patriot]

Octane by itself does not add power to your engine.

However, a low-octane fuel will not allow a performance engine to achieve its optimal ignition timing and power due to detonation. Detonation is defined as uncontrolled combustion where high cylinder pressure can auto-ignite end gases in the cylinder that tend to increase the opportunity for this process to be self-sustaining. This creates a massive pressure spike that literally rattles the pistons in their cylinders and kills power.

Using a higher-octane fuel allows an engine to take advantage of an ideal timing curve without causing detonation. (Our trucks are optimized for 89 octane fuel)

Once that timing has been achieved, there is no advantage to using higher-octane fuel.

 

[Timeless]

Octane by itself does not add power to your engine.

However, a low-octane fuel will not allow a performance engine to achieve its optimal ignition timing and power due to detonation. Detonation is defined as uncontrolled combustion where high cylinder pressure can auto-ignite end gases in the cylinder that tend to increase the opportunity for this process to be self-sustaining. This creates a massive pressure spike that literally rattles the pistons in their cylinders and kills power.

Using a higher-octane fuel allows an engine to take advantage of an ideal timing curve without causing detonation. (Our trucks are optimized for 89 octane fuel)

Once that timing has been achieved, there is no advantage to using higher-octane fuel.

Yup yup. However I am not sure I agree that 93 octane gets worse mileage than 89.

 

[RAM Patriot]

Yup yup. However I am not sure I agree that 93 octane gets worse mileage than 89.

Our HEMI engines are optimized to run on 89 octane fuel.

If your ECM can advanced the timing enough to take advantage of 93 octane fuel or if you are running a tune on your truck that is optimized for high octane fuel than I would agree that your truck would get better gas mileage from the 93 octane fuel. Otherwise, you will be wasting a huge amount of money paying for high octane gasoline.

 

[41magmag41]

The trouble is that Sams and Cosco offer hi test at a lower cost than most fuel outlets charge for midgrade 89, so why not run the higher octane and cheaper than the mid grade 89??

 

[RAM Patriot]

The trouble is that Sams and Cosco offer hi test at a lower cost than most fuel outlets charge for midgrade 89, so why not run the higher octane and cheaper than the mid grade 89??

As I stated above as long as your truck is advancing the timing to take advantage of the higher octane fuel and you are getting more HP and MPG from the 93 octane fuel at a lower price point.

Go for it...

 

[SD Rebel]

My question is, if the Hemi engine is tuned for 89, even assuming the ECU isn't flexible enough to use 91/93, won't it still use an 89 tune even with say 93 octane?

So I don't get how you lose hp or drop mpg by using a higher octane than 89? Or is the people that posted that are using anecdotal experiences only?

As for me, I've noticed zero difference with any octane 87, 89 or 91 in performance and mpg. However, not sure if you would notice a slight increase in power with a 4800 lbs truck. I think I would notice it more if I was towing where detonation would come into play, but I haven't tried using 87 while towing.

 

[Scap]

My question is, if the Hemi engine is tuned for 89, even assuming the ECU isn't flexible enough to use 91/93, won't it still use an 89 tune even with say 93 octane?

So I don't get how you lose hp or drop mpg by using a higher octane than 89? Or is the people that posted that are using anecdotal experiences only?

As for me, I've noticed zero difference with any octane 87, 89 or 91 in performance and mpg. However, not sure if you would notice a slight increase in power with a 4800 lbs truck. I think I would notice it more if I was towing where detonation would come into play, but I haven't tried using 87 while towing.

Yes the "tune" will be for 89.
91/93 are more difficult to burn than 87/89, so that could equate to less power.

Biggest question, is how did you get your truck down to 4800#????

 

[RAM Patriot]

My question is, if the Hemi engine is tuned for 89, even assuming the ECU isn't flexible enough to use 91/93, won't it still use an 89 tune even with say 93 octane?

So I don't get how you lose hp or drop mpg by using a higher octane than 89? Or is the people that posted that are using anecdotal experiences only?

As for me, I've noticed zero difference with any octane 87, 89 or 91 in performance and mpg. However, not sure if you would notice a slight increase in power with a 4800 lbs truck. I think I would notice it more if I was towing where detonation would come into play, but I haven't tried using 87 while towing.

I cannot speak from personal experience since I have not run 93 octane in my truck. I do however burn 90 octane non-ethanol fuel and have notices an increase in MPG and HP without any knock.

Based on research and physics higher octane fuel requires more heat and more precision to burn correctly. Therefore, the timing and tune would need to be different and possibly different plugs to take advantage of the higher octane fuel.

 

[SD Rebel]

Yes the "tune" will be for 89.
91/93 are more difficult to burn than 87/89, so that could equate to less power.

Biggest question, is how did you get your truck down to 4800#????

That makes sense, lol 4,800 was my F150s weight. I think my Rebel is about 5,300 hundred.

 

[SD Rebel]

I cannot speak from personal experience since I have not run 93 octane in my truck. I do however burn 90 octane non-ethanol fuel and have notices an increase in MPG and HP without any knock.

Based on research and physics higher octane fuel requires more heat and more precision to burn correctly. Therefore, the timing and tune would need to be different and possibly different plugs to take advantage of the higher octane fuel.

Wish I could get non-ethanol in my area, but everything is 10% unless you get 100 octane or aviation/boat fuel which I think aren't car rated.

 

[HSKR R/T]

And......if the 91 isn't fresh gas.....your mixing old gas in, so that throws your theory out the window

Why would 91 not be fresh? Plenty of people drive performance cars, and just read this thread to see how many people run premium fuel thinking it's better for the truck.

 

[SD Rebel]

My local Costco is so busy, it' gets a fuel truck delivery at least once a day. Hundreds of cars roll in every hour, I don't think I will find old fuel there regardless of octane.

Plus it takes a while before fuel goes bad, they say a few months, but I had 91 octane in a gas container without Stabil that stayed good for over a year. I doubt most gas stations will have premium last beyond a couple of weeks for a slow station, much less months.

 

[Scap]

That makes sense, lol 4,800 was my F150s weight. I think my Rebel is about 5,300 hundred.

My 13 F150 SCrew FX4 was +6k# with me in it at the track.

 

[JJRamTX]

Being at High altitude (~7000 feet) our basic gas is 85 octane. 95%+ of the time I get gas at Costco and I have ran that without any issues for 46,000+ miles (Including 15,000+ miles of towing). I think the lack of oxygen in the air makes the mixture with 85 octane work fine since I have never experienced any knocking or pinging. After reading this thread I might try a tank of 89-91 octane and see if I notice a big difference in either mileage or power.

 

[SD Rebel]

My 13 F150 SCrew FX4 was +6k# with me in it at the track.

Mine was a 2015 XLT Supercab 2WD, aluminum body and 2.7L Ecoboost. But she was quick!

 

[Stryker6040]

i use 87 in the winter and 89 or higher in the summer when AC will be used

 

[TravisJ]

I am pretty sure any gas station has someone with common sense ordering their gas. If you barely sell 91 you probably aren’t filling the tank to the top so it sits forever.

But as someone said it lasts so long I doubt it’s that big of an issue.

 

[LakesAZ]

See my post #118 for the Costco gas usage if you are concerned about not utilizing all of the 91 octane from Costco, just make your own 89 octane.

I use the half tank fill up method at Costco. One time 87 octane and at the half tank mark, fill it will 91.

 

[SD Rebel]

See my post #118 for the Costco gas usage if you are concerned about not utilizing all of the 91 octane from Costco, just make your own 89 octane.

I use your method of filling with 91 octane, drive down to nearly half a tank, then fill with 87.

I wouldn't dare try that in one sitting unless for some rare occasion no one is behind me in line. On a busy day, the person behind you is making sure you don't take too long putting your pin in the card reader, I can't imagine what would happen if I tried to fill up with two different octanes, lol