Sold on 89 Octane

[morrisl29]

Perhaps higher octane played a role in your improved mileage but I suspect elevation change, wind, and speed factored more. Candidly there is no way a 2 point octane boost alone would increase your gas mileage by nearly 20%.

Granted 20% is high, but it’s more like 15%. I agree it’s still on the high side. As for elevation Denver is around 5000 feet, and the western part of Kansas is about 3000 ft. Environmental conditions will also play part. On this day the difference in weather between Denver and Kansas was negligible. However, my hands on experience from my gear head days (30 years ago) tells me that timing has a huge effect on engine performance. I also expect that the octane is not the only factor giving the better performance. But I don’t know enough about the refining process to speculate. It’s my understanding that there are different grades of gas, even within the same octane rating. Like I said this is anecdotal. As such it should not be taken as evidence proving the theory.

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[aeonixx1001]

Some may disagree but where I live (about 500 ft elevation) using 89 over 87 in the 3.6 gives it a bit of mpg & better torque. I only use top-tier fuel regardless of octane.

They have a Gas station here in Phoenix that carries 110, with a note on the pump saying the attendant has to pump it. I haven't ever seen anything higher than 92-93. (Which I use). I would like to know what the hell that 110 is like if you had an engine left after starting...

 

[morrisl29]

The 'off brand' stations buy on the open market so you likely get the same gas as a brand station. Only difference might be the top tier stations who add more detergent. Use of detergent debatable on DI engines anyhow.

Knock can be detected by the ECU well before pinging occurs, and the timing adjusted accordingly. Basically it is a pressure wave that increases in amplitude as you get closer to knock.

I did a little research on knock sensers. I found that the most sensitive senser is a piezoelectric sensor. It’s described by a manufacturer as detecting vibration in the engine. It seems to me if you have a vibration this is pinging. Even it’s not auditable outside the engine compartment. The severity may differ, but pre-detonation is always detrimental to the efficient operation of an engine.

 

[MBrady78]

Just saw this over the weekend.



Lots of "Myths" busted about octane.

 

[morrisl29]

They have a Gas station here in Phoenix that carries 110, with a note on the pump saying the attendant has to pump it. I haven't ever seen anything higher than 92-93. (Which I use). I would like to know what the hell that 110 is like if you had an engine left after starting...

Back in the day 110 octane was also called Av gas, short for aviation gas. The octane rating does not correspond to more BTUs in the fuel. ie it’s not more explosive. It simply lets you run a higher compression ratio in your cylinder with more timing. Those do equate to more horsepower and more torque. The drawback is the way they get to 110 Octane. The only way I know to truly reach 110 is with the use of lead additive. If you put a gas with lead in a car with a catalytic converter, you will plug the converter. I would guess it would not be compatible with other components in a modern vehicle either.

 

[TheRaven]

I did a little research on knock sensers. I found that the most sensitive senser is a piezoelectric sensor. It’s described by a manufacturer as detecting vibration in the engine. It seems to me if you have a vibration this is pinging. Even it’s not auditable outside the engine compartment. The severity may differ, but pre-detonation is always detrimental to the efficient operation of an engine.

This is something that is clearly not well understood here. Modern engine control systems run continuously and constantly on the ragged edge of predetonation. It doesn't matter what fuel you put in - the computer works the same - advance timing until knock is detected, then back off slightly, then advance again until knock is detected and back off...this is done continuously, many times per second, regardless of what grade of fuel you use. Yes, theoretically, higher octane SHOULD allow the controller to advance FURTHER than lower octane and thus produce more power...but there are so many other factors that can be even more powerful than octane in this equation, and modern engines are so vigorously optimized for efficiency that gains from fuel quality and octane are going to be extremely minimal. Really the only way to actually see gains is to change the rules that the controller operates by so to speak - i.e. a tune - that either sacrifices efficiency in favor of power or vice versa.

The end result is this - if you are experiencing knock that is not being quickly handled by your engine controller, you have a problem. It won't be fixed by octane. It is either a result of a malfunction under the hood or something you are doing. You need to figure out what is broken, or stop doing whatever you are doing that is causing the knock. Failing to do those things will only result in a much bigger problem later.

 

[Slate]

Ever since working from home, I put very few miles on my Jeep or F150 (both have turbos). I have been putting in the higher octane seeing as how the vehicles will sit longer than they used to. I know that octane levels don't equal staleness, but it surely can't hurt.

Plus my Jeep is a 4xe and most of my errands are on electric anyway, but I feel like the Jeep sounds better when/if it turns the ICE on - usually due to a heavy pedal.

In my F150, I certainly feel it drives smoother on longer trips, but as someone said before how much is placebo and how much is real is a good question.

I will say this, I had a Jeep Grand Cherokee years ago (like 2002) with the V8 engine, etc. The RPM's would bounce, especially at idle. I eventually put in the highest octane and a can of seafoam and after some spirited driving, the idle went steady. Been a fan since, but who knows?

 

[NWJeepr]

I will say this, I had a Jeep Grand Cherokee years ago (like 2002) with the V8 engine, etc. The RPM's would bounce, especially at idle. I eventually put in the highest octane and a can of seafoam and after some spirited driving, the idle went steady. Been a fan since, but who knows?

Was probably the seafoam, not the octane. Seafoam is basically solvent and moisture, and it probably cleaned some crud out of an injector or the throttle body

 

[aeonixx1001]

Ever since working from home, I put very few miles on my Jeep or F150 (both have turbos). I have been putting in the higher octane seeing as how the vehicles will sit longer than they used to. I know that octane levels don't equal staleness, but it surely can't hurt.

Plus my Jeep is a 4xe and most of my errands are on electric anyway, but I feel like the Jeep sounds better when/if it turns the ICE on - usually due to a heavy pedal.

In my F150, I certainly feel it drives smoother on longer trips, but as someone said before how much is placebo and how much is real is a good question.

I will say this, I had a Jeep Grand Cherokee years ago (like 2002) with the V8 engine, etc. The RPM's would bounce, especially at idle. I eventually put in the highest octane and a can of seafoam and after some spirited driving, the idle went steady. Been a fan since, but who knows?

Sea Foam- The miracle that no one knows about. It's cool to see that someone else is wise to the sea foam trick....

 

[jellis4148]

I don't think it's really the octane that matters. I think it's the ethanol. If you can find fuel without any ethanol I think they run better, and get better economy. That is the only reason I buy 91 octane. It's the only fuel I can get in Missouri that contains 0 ethanol. I'm sure running higher octane helps with spark knock and all that.

 

[jellis4148]

Sea Foam- The miracle that no one knows about. It's cool to see that someone else is wise to the sea foam trick....

Top tier fuel is the way to go especially on direct injection engines. The top tier fuel helps keep the top side of the intake valve from getting carbon on it since you don't have fuel washing over them like a port injected engine.

 

[azjl#3]

As consistent as I can get on the road, mostly hiway, mountainous, my 2023 3.6 etorque, which did get 18.5, over a few months of using 91mpg rose to 22, and has settled at 21.4mpg over 1,000 miles. Now I will go back to 87 and see if it drops.

I tried 3 weeks of 91 with wife's 2021 G Cherokee 3.6, it usually gets 22mpg, and is now getting 23mpg, to close to call, not enough trial.

 

[azjl#3]

Just saw this over the weekend.



Lots of "Myths" busted about octane.

So, they seem to bust the octane myth, yet before they do one pull, they admit they would use at least 91 in a real car because of real world issues.

The 91 pull showed a percentage point better torque, which is what we use going up hills, leaving a light.

I'm not surprised timing did not change.

They admitted the engine ran leaner with the 91, which is exactly how you improve mileage.

Previous poster noted our computer is always running into and out of lean and changing mixture based on knock. That also helps MPG and something I don't think engine masters did, they manually adjusted parameters.

BTW, I am not sold on using higher octane, just trying it out.

 

[Nokones]

They have a Gas station here in Phoenix that carries 110, with a note on the pump saying the attendant has to pump it. I haven't ever seen anything higher than 92-93. (Which I use). I would like to know what the hell that 110 is like if you had an engine left after starting...

Is that the Loves Truck Stop at Wildhorse?

 

[YBABRAT]

Did a round trip of 65 miles today. More traffic than usual, so MPG took a hit. I got 23.8 MPG. All in all I never saw my average go below 22.9 MPG.

On a side note... pedal monster is a smart throttle controller. So it probably is relearning the engines response to load and throttle. I will continue to monitor and make a followup with pure gas 93 octane mix with pure gas 87 octane. Just have to get my GPS maps out and locate the stations near my route. At least I know I can get 93... a friend said I can get 103 race fuel near by. That is a bit much for testing mpg and octane.

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