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[TSO_NJ]

Ok you might have me there but I still stand by my 93 octane rating for better performance

Higher-octane fuels help to mitigate pre-ignition events while ensuring proper combustion and higher output for performance engines." (source: MOTORTREND, October 9, 2019)

And no it’s not a race car I know that and I don’t treat it as such, I have my Mustang for that. We could debate this till the cows come home. The only reason I use 93 is because my local BJ’s only carries 87 & 93.

I found this test by Car & Driver, yes I know it’s a true performance car it still is what it is. We can find out all kind of information on the internet, just my 2 cents I still believe that 93 is better than 87.


The mere thought of pumping regular unleaded into this $129,595 intercontinental ballistic missile felt wrong. BMW explicitly warns about engine damage from doing so, and while that seemed unlikely in such mild temperatures, using the cheap stuff would have been wildly out of touch with what an owner would do (at least until this M5 reaches its fourth owner sometime in 2036). BMW requires 91-octane fuel at a minimum, with 93 recommended, so we did just that, switching between the common forms of premium gas depending on which state you're in. Are Californians, with their watered-down premium, leaving something on the table? We wanted to know.

The dyno results shocked us. Not because of the 13-hp difference between 91 and 93 octane. No, that delta was in line with expectations. Our jaws were left hanging by just how much power and torque we measured. On either fuel, the über 5-series is seriously underrated. While BMW claims 617 horsepower at the crank, the dyno reports it makes that much at the wheels (after driveline losses) on 93-octane premium. And both fuels produced significantly more torque than BMW's advertised 553 lb-ft.

The higher-octane fuel trimmed a single tenth of a second across all of the M5's acceleration times. That results in a time-bending 2.7-second slingshot to 60 mph and 10.8 seconds through the quarter-mile and lands this five-seat, 4246-pound four-door squarely in the realm of supercars. The BMW also claimed the largest fuel-economy margin in the test, but the 0.7-mpg difference favored the lower octane. The M5 Competition stands as proof that the octane rating does make a difference, although in the case of these two premium fuels, if you're forced to use 91 octane, you're hardly missing out.

According to my Outer Banks owner's manual (page 163) you're correct (I just learned something new):

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[Deleted member 6350]

That would only be true if it also included additional cleaning additives. Higher octane gas by itself is not an influence on cleaning your engine.

Well according to this article higher octane does clean better !!! So who’s right ??? Like I said earlier we could go on an on about this. You like what you like and I like what I like. That’s all. Steve

 

[Escape2Bronco]

Well according to this article higher octane does clean better !!! So who’s right ??? Like I said earlier we could go on an on about this. You like what you like and I like what I like. That’s all. Steve

Not trying to be argumentative, but top tier doesn’t mean high octane. You can get a top tier gasoline at 87 octane that still includes the cleaning additives. My point was that a higher octane doesn’t mean cleaner running just in itself.

 

[rocks]

Not trying to be argumentative, but top tier doesn’t mean high octane. You can get a top tier gasoline at 87 octane that still includes the cleaning additives. My point was that a higher octane doesn’t mean cleaner running just in itself.

Higher octane gas supposedly has more cleaning additives.

 

[sajohnson]

I had no idea! I originally thunk is was the opposite (burn rate). ?

"Fueling Basics: Explaining Octane Ratings

Octane ratings are plastered all over every gas pump, and, contrary to marketing terminology, "premium" does not necessarily indicate a fuel is "better" for your car as much as whether it is "right" for your car. Fuel with an 87 octane rating burns more quickly while higher-octane fuels burn more slowly. In engines designed for standard unleaded fuel, efficiency and performance is optimized for 87 octane and could actually perform worse with higher-octane fuel since the burn rate is slower. By contrast, a higher-performing engine, which includes engines with higher compression ratios and/or forced induction, requires the slower burn rate of higher-octane fuels to defend against engine knock. Knocking or pre-ignition occurs when the air/fuel mixture ignites before intended. This happens because higher compression ratios and cylinder pressures cause the air/fuel mixture to heat up, and, in some cases, ignite prematurely. Knocking that goes unchecked inevitably leads to engine damage. Higher-octane fuels help to mitigate pre-ignition events while ensuring proper combustion and higher output for performance engines." (source: MOTORTREND, October 9, 2019)

Good info!

A large factor is how an engine is designed. Is it intended to run on 91 or 93 octane ONLY?

Is it intended to run on 91 or 93 octane, but will not be harmed by 87 or 89 octane -- just have significantly reduced performance?

Or is it designed to run well -- under most circumstances -- on 87+?

Th BS is in the last category. According to Ford, 87 is adequate under normal conditions, but for optimum performance, 91+ is recommended.

However, things change when the BS is operated under a heavy load (towing and/or a bulky load on the roof) esp in hot ambient temps and/or up steep mountain grades. Under those conditions the improved performance from 91+ octane is most noticeable.

Cleaning ability: As has been pointed out above, all grades of "Top Tier" gas have the same additives -- regardless of octane.

Cost: The price difference between 87 and 91/93 has gotten stupid. I recall when it was 10 cents or less. That said, if, like my wife and I, a BS owner does not put a lot of miles on their vehicle, the additional cost of premium fuel is negligible -- so why not enjoy the extra performance? That's my thinking anyway, but if we were each driving 20,000+ mils/year like we used to, I'd be hesitant to spend the extra money -- under normal operating conditions. I would not hesitate to us 93 when working the BS BL hard.

 

[gatornek]

The ONLY thing higher 93 octane gas does is resist knock better. That's it. There's no fuel economy and there's d@mn sure no savings economy. However, I'm of the opinion that these engine 'knock' a lot. Maybe not full blown pre-ignition, but if you're using 87 gas, I can promise you that your performance of your engine could be a lot better with 93. It's just a cleaner combustion, post spark.

But everyone here is absolutely right. Opting for 93 used to mean an extra quarter. Now it means, a dollar in some cases. Its why I religiously go to Costco. In fact, during a recent road trip to NC from Florida, my Brother in law that was behind us during the trip raised eyebrows as I planned our stops around Costco gas stations. But I don't care. I've been habitually trying to get best performance vs lowest buck, and Im not gonna break my habits for no one. ?

 

[gatornek]

Higher octane gas supposedly has more cleaning additives.

Negative. Its strictly a different mix of the type of hydrocarbons. There is one type of hydrocarbon that is more resistant to knock than the other. The gas manufacturers play with mixtures of the two to get the different knock ratings.

All branded gas has the same detergent. If you buys Exxon gas, it has the same detergents across the board. Same as any other.

 

[TSO_NJ]

Good info!

A large factor is how an engine is designed. Is it intended to run on 91 or 93 octane ONLY?

Is it intended to run on 91 or 93 octane, but will not be harmed by 87 or 89 octane -- just have significantly reduced performance?

Or is it designed to run well -- under most circumstances -- on 87+?

Th BS is in the last category. According to Ford, 87 is adequate under normal conditions, but for optimum performance, 91+ is recommended.

However, things change when the BS is operated under a heavy load (towing and/or a bulky load on the roof) esp in hot ambient temps and/or up steep mountain grades. Under those conditions the improved performance from 91+ octane is most noticeable.

Cleaning ability: As has been pointed out above, all grades of "Top Tier" gas have the same additives -- regardless of octane.

Cost: The price difference between 87 and 91/93 has gotten stupid. I recall when it was 10 cents or less. That said, if, like my wife and I, a BS owner does not put a lot of miles on their vehicle, the additional cost of premium fuel is negligible -- so why not enjoy the extra performance? That's my thinking anyway, but if we were each driving 20,000+ mils/year like we used to, I'd be hesitant to spend the extra money -- under normal operating conditions. I would not hesitate to us 93 when working the BS BL hard.

Good clarification. Octane requirements aligns with page 163 of the owner’s manual.

 

[Mark S.]

From the Motortrend article: "Knocking or pre-ignition occurs when the air/fuel mixture ignites before intended."

This is not exactly true. "PRE-IGNITION" is when the mixture ignites before intended, i.e. before the spark plug fires. Detonation occurs when the increasing heat and pressure from the ignition event--i.e. AFTER the spark plug has fired--causes the mixture to spontaneously ignite in other areas of the combustion chamber. This results in two (or more) flame fronts propagating in the combustion chamber at the same time. The "knock" or "ping" is the sound of those flame fronts colliding.

The video at this link graphically illustrates the difference.

There is so much confusion around the web regarding these two phenomenon (detonation vs pre-ignition), which is unfortunate, because they are often conflated. Pre-ignition is an engine killer. If the mixture ignites before the spark has fired then the pressure from the combustion event is pushing down on the piston while it is still traveling upward on its compression stroke (see the video linked above for a visual). All the momentum of the engine spinning is pushing the piston upward against that growing pressure. Pre-ignition can destroy an engine after a single event.

Detonation, on the other hand, is a normal occurrence for the operation of some engines, including Ford's EcoBoost series. The PCM (powertrain control module) modulates various engine parameters (ignition timing, mixture, etc.) to optimize power output while avoiding prolonged or heavy detonation. It does this by ramping up power output while "listening" for the telltale knock or ping with acoustic sensors. At the first indication of detonation the PCM clamps down power output to a level just below where detonation first occurred. If you're paying attention, that means the engine must operate at light detonation for the PCM to work correctly. This operation pattern occurs whether you use regular or premium. The only difference is at what power level detonation first occurs. Engine heat increases with power output. With regular gas, detonation occurs at a lower power output than with premium. This is because premium requires greater heat/pressure to ignite, which means the PCM may increase power output to a higher level before detonation first occurs.

Use premium fuel if you need it (prolonged high power demand, such as towing on a hot day), or if you simply like the way your engine runs. I've noticed better throttle response and definitely more pep when using premium fuel in my car. But there's no reason to believe the use of premium will net better fuel mileage or in any way increase your engine's longevity or durability. Now that you know how it works you know it will experience the same light detonation no matter what fuel you use. It's programmed that way.

 

[Mark S.]

The price difference between 87 and 91/93 has gotten stupid. I recall when it was 10 cents or less.

I'm almost certain that gasoline producers are capitalizing on consumer ignorance. "Premium" is obviously "better" than "regular" via the magic of marketing. I don't believe there is enough difference in the refining process to justify the cost difference. If anyone has any data on that please share.

 

[rocks]

Well, all I can say is 87 works but premium is recommended. Use whatever you want. Of course, they won't say to use premium exclusively because Ford would lose sales but Ford does say...

"For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel is most noticeable in hot weather as well as other conditions, for example when towing a trailer."

 

[TSO_NJ]

From the Motortrend article: "Knocking or pre-ignition occurs when the air/fuel mixture ignites before intended."

This is not exactly true. "PRE-IGNITION" is when the mixture ignites before intended, i.e. before the spark plug fires. Detonation occurs when the increasing heat and pressure from the ignition event--i.e. AFTER the spark plug has fired--causes the mixture to spontaneously ignite in other areas of the combustion chamber. This results in two (or more) flame fronts propagating in the combustion chamber at the same time. The "knock" or "ping" is the sound of those flame fronts colliding.

The video at this link graphically illustrates the difference.

There is so much confusion around the web regarding these two phenomenon (detonation vs pre-ignition), which is unfortunate, because they are often conflated. Pre-ignition is an engine killer. If the mixture ignites before the spark has fired then the pressure from the combustion event is pushing down on the piston while it is still traveling upward on its compression stroke (see the video linked above for a visual). All the momentum of the engine spinning is pushing the piston upward against that growing pressure. Pre-ignition can destroy an engine after a single event.

Detonation, on the other hand, is a normal occurrence for the operation of some engines, including Ford's EcoBoost series. The PCM (powertrain control module) modulates various engine parameters (ignition timing, mixture, etc.) to optimize power output while avoiding prolonged or heavy detonation. It does this by ramping up power output while "listening" for the telltale knock or ping with acoustic sensors. At the first indication of detonation the PCM clamps down power output to a level just below where detonation first occurred. If you're paying attention, that means the engine must operate at light detonation for the PCM to work correctly. This operation pattern occurs whether you use regular or premium. The only difference is at what power level detonation first occurs. Engine heat increases with power output. With regular gas, detonation occurs at a lower power output than with premium. This is because premium requires greater heat/pressure to ignite, which means the PCM may increase power output to a higher level before detonation first occurs.

Use premium fuel if you need it (prolonged high power demand, such as towing on a hot day), or if you simply like the way your engine runs. I've noticed better throttle response and definitely more pep when using premium fuel in my car. But there's no reason to believe the use of premium will net better fuel mileage or in any way increase your engine's longevity or durability. Now that you know how it works you know it will experience the same light detonation no matter what fuel you use. It's programmed that way.

Screen shots from your video link:

 

[gatornek]

From the Motortrend article: "Knocking or pre-ignition occurs when the air/fuel mixture ignites before intended."

This is not exactly true. "PRE-IGNITION" is when the mixture ignites before intended, i.e. before the spark plug fires. Detonation occurs when the increasing heat and pressure from the ignition event--i.e. AFTER the spark plug has fired--causes the mixture to spontaneously ignite in other areas of the combustion chamber. This results in two (or more) flame fronts propagating in the combustion chamber at the same time. The "knock" or "ping" is the sound of those flame fronts colliding.

The video at this link graphically illustrates the difference.

There is so much confusion around the web regarding these two phenomenon (detonation vs pre-ignition), which is unfortunate, because they are often conflated. Pre-ignition is an engine killer. If the mixture ignites before the spark has fired then the pressure from the combustion event is pushing down on the piston while it is still traveling upward on its compression stroke (see the video linked above for a visual). All the momentum of the engine spinning is pushing the piston upward against that growing pressure. Pre-ignition can destroy an engine after a single event.

Detonation, on the other hand, is a normal occurrence for the operation of some engines, including Ford's EcoBoost series. The PCM (powertrain control module) modulates various engine parameters (ignition timing, mixture, etc.) to optimize power output while avoiding prolonged or heavy detonation. It does this by ramping up power output while "listening" for the telltale knock or ping with acoustic sensors. At the first indication of detonation the PCM clamps down power output to a level just below where detonation first occurred. If you're paying attention, that means the engine must operate at light detonation for the PCM to work correctly. This operation pattern occurs whether you use regular or premium. The only difference is at what power level detonation first occurs. Engine heat increases with power output. With regular gas, detonation occurs at a lower power output than with premium. This is because premium requires greater heat/pressure to ignite, which means the PCM may increase power output to a higher level before detonation first occurs.

Use premium fuel if you need it (prolonged high power demand, such as towing on a hot day), or if you simply like the way your engine runs. I've noticed better throttle response and definitely more pep when using premium fuel in my car. But there's no reason to believe the use of premium will net better fuel mileage or in any way increase your engine's longevity or durability. Now that you know how it works you know it will experience the same light detonation no matter what fuel you use. It's programmed that way.

Might as well pin in this at the top of the forum. The details here are pretty which what everyone needs to understand.

 

[TSO_NJ]

Might as well pin in this at the top of the forum. The details here are pretty which what everyone needs to understand.

I like this idea! Added to OP.

 

[MJS54]

From the BS manual. Yes, 87 is fine but for optimum performance ...

"For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended. The performance gained by using premium fuel is most noticeable in hot weather as well as other conditions, for example when towing a trailer."

Yup, started using 93 after the dealer’s 87 was just about gone…huge difference in idling smoothness and much better throttle response…

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