Premium vs. Regular fuel data point

[GPSMan]

I'm driving around the "Top Tier" of the continent. Alaska and Yukon Territory.

All they sell up here is 87.
For 1000 miles (maybe more?) All I've seen is 87. Have no idea if ethanol is here. Stuff is not labeled. But when you see gas, you are happy to have it.
Once I pumped gas from a small above ground tank (2500 gal) using a small gas generator to pump the gas. Definitely off-grid.

So this does not contradict anything here in this thread, but does contradict those that say they "must" have premium. They for sure don't. Some areas, some WIDE areas don't even sell it.

It's a nicety. Not a necessity.

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[TxMike64]

Another thing to consider RE: 91 vs 93
Ford programs to ECU to be best suited to 91 average. And the engines performance also affected by ambient conditions as COBB mentioned. All manufacturers will recommend using fresh top tier fuels. Most people use either 87 (regular) or 93 (premium) - it appears to me that very few opt to use 91 (plus/midgrade). So if you want the freshest fuel use 87 (Regular) or 93 (premium), avoiding midgrade. edit: Old fuel oxidizes, reducing the octane rating, and can absorb water.

Now this varies where you are: Here in Texas regular is 87 and premium is 93, and it's easy to find 93. But up north regular is 85 and premium is 91, and you can't always find premium (91). In some parts of Nebraska I've seen where your only options are 87(E15) or E85.

In response to someone's comment earlier about the ECU detuning to KOM -1 from running 87: it's not done with the cam phasers. Cam phasers are triggered by RPM. Detuning in this sense is done mostly with ignition timing, and to a lesser degree with injector timing and pulse-width. Running 87 will not wear out the cam phasers.

 

[MaverickHopefulOwner]

This is a great demonstration of Ford's octane learning strategy and the impact it can have on vehicle performance.

The ECU is constantly listening to the feedback from the knock sensors on the engine. Knock, or detonation, is the spontaneous combustion of air and fuel after the spark plug has fired in the cylinder. As cylinder pressure and heat builds with the propagating flame-front of the combustion event, pockets of air and fuel in the cylinder can spontaneously and explosively combust before the flame-front ignites it. This is a knock event, and in very high cylinder pressures can cause significant damage to pistons/rods/rod bearings/head gasket integrity/etc. These knock events produce a distinct ringing in the engine that the knock sensor is carefully calibrated to recognize - the knock sensor is basically a very finely tuned microphone listening for specific sound frequencies that happen when knock events occur.

Octane is a measurement of a fuel's resistance to spontaneous combustion like knock. Higher octane fuels can withstand higher pressures and temperatures within the combustion chamber without knocking. The Maverick (and all other modern Fords) ECU's goal is to infer octane based on the frequency and intensity of knock events.

If the ECU detects a series of knock events that result in a significant amount of timing retard to be applied, it will lower the inferred octane by decreasing the Knock Octane Modifier (KOM). For those familiar with some slightly older Fords, you may be familiar with the term Octane Adjust Ratio (OAR) - this is practically speaking the exact same system.

KOM can learn between +1 (highest possible learned octane) and -1 (lowest possible learned octane). If you've been driving around with 93 OCT in the tank, run it dry, and then refill with 87 OCT, the knock events that the engine detects with the knock sensors will decrease the learned KOM value.

KOM is used to modify the amount of total ignition advance and airflow limiters. When KOM is 1, the KOM-based timing compensation will add anywhere between 3-5* of ignition timing advance. When KOM is -1, it will remove that same amount (creating a difference in final ignition timing of anywhere from -6* to -10* compared to KOM at +1).

Airflow limiting is done via three tables that blend based on inferred octane. This one is also a longer explanation, but you can expect to lose a few PSI of boost pressure when KOM is -1 compared to +1.

KOM will tend to settle in anywhere between -0.5 and 0 on 87 OCT, and the stock tune will see KOM at +1 with 91 OCT or higher. Expect 20-30WHP lost by running 87 OCT instead of 91/93 OCT, with similar torque losses.

Another thing related to KOM/octane learning to help you analyze dyno charts for "baseline" pulls: Even if you're running 93 OCT, if you reset the ECU the stock tune will default KOM to 0. If a dyno pull is done on the stock tune immediately after a reset without giving the ECU the opportunity to learn up to the appropriate KOM that matches the real fuel quality, you'll get a "baseline" run that makes significantly less power than it should, artificially increasing the power gain comparing stock to tuned. We ALWAYS baseline our vehicles with the octane learning system fully up to +1 and on the same tank of fuel used for tuned power pulls, as shown in our dyno charts for advertised power gains.

Not that I am that worried about performance on a Hybrid 191HP truck, but good information. I had questions about how the knock sensors worked to reduce knock.

 

[Montana]

I'm driving around the "Top Tier" of the continent. Alaska and Yukon Territory.

All they sell up here is 87.
For 1000 miles (maybe more?) All I've seen is 87. Have no idea if ethanol is here. Stuff is not labeled. But when you see gas, you are happy to have it.
Once I pumped gas from a small above ground tank (2500 gal) using a small gas generator to pump the gas. Definitely off-grid.

So this does not contradict anything here in this thread, but does contradict those that say they "must" have premium. They for sure don't. Some areas, some WIDE areas don't even sell it.

It's a nicety. Not a necessity.

Higher octane is harder to burn and the cold temps prevent detonation. Plus, there is the factor of availability in many rural spots. More populated places up North will offer 90. Lots of places where fuel is flown in also limits choice. It's a lot colder up North. Plenty of engines that perform better on higher octane fuel, but in those cold and rural areas it's a question of availability, temperature and detonation. Cost comes into play too, obviously, especially when considering transport and taxes.

 

[SkrubbinBubb1es]

Has anyone ran 89 octane? Top Tier only of course. Seems like a good half way point for daily driving.

 

[TxMike64]

89 is midgrade. see my comments above.

 

[GPSMan]

Another thing to consider RE: 91 vs 93
Ford programs to ECU to be best suited to 91 average. And the engines performance also affected by ambient conditions as COBB mentioned. All manufacturers will recommend using fresh top tier fuels. Most people use either 87 (regular) or 93 (premium) - it appears to me that very few opt to use 91 (plus/midgrade). So if you want the freshest fuel use 87 (Regular) or 93 (premium), avoiding midgrade. edit: Old fuel oxidizes, reducing the octane rating, and can absorb water.

Now this varies where you are: Here in Texas regular is 87 and premium is 93, and it's easy to find 93. But up north regular is 85 and premium is 91, and you can't always find premium (91). In some parts of Nebraska I've seen where your only options are 87(E15) or E85.

In response to someone's comment earlier about the ECU detuning to KOM -1 from running 87: it's not done with the cam phasers. Cam phasers are triggered by RPM. Detuning in this sense is done mostly with ignition timing, and to a lesser degree with injector timing and pulse-width. Running 87 will not wear out the cam phasers.

I do not like your post above.

You did not know that "mid-grade" does not exist so it never goes "stale".

They only ship regular and premium.
They only store regular and premium.

When you select "mid grade" it pumps half & half into your tank.

 

[NJBob]

Which gasoline supplier out there carries no ethanol fuel? It's something I just don't see here in central Texas.

Not in NJ either. I know other states have it.

 

[Dmthomp32]

I’ve been using 93, high octane in my Mav. My biggest difference is how the engine sounds, seems to have far less knocking and tings. Doesn’t sound as much like a sewing machine. That said it does get better mileage, but I’ve noticed that my mileage is impacted more by me turning off the AC versus my fuel choices. While driving in the summer in NC, you want AC but when I’ve turned it off it has been noticeably improved.

 

[rlhdweman]

I do not like your post above.

You did not know that "mid-grade" does not exist so it never goes "stale".

They only ship regular and premium.
They only store regular and premium.

When you select "mid grade" it pumps half & half into your tank.

True now for most places, but not that long ago many fuel stations had 3 tanks underground for each grade & that was ok before ethanol, but with ethanol the 'shelf life' is not as long & it would sit in the tank unused, I worked at a station for 8 years & midgrade was something few used. Now we have 87e10 & 91 without ethanol, so we have 89e5 for midgrade mixed by the pumps.

 

[NJBob]

Not in NJ either. I know other states have it.

One thing I do is buy non ethanol gas in small cans for my garden tools. It's very expensive but the machines run alot better and has a longer shelf life.

 

[TxMike64]

Which gasoline supplier out there carries no ethanol fuel? It's something I just don't see here in central Texas.

Its available in Central Texas, you just need to know where it's available. VP stations, and some Shell stations. VP also has 105 octane.

 

[JimCT]

Has anyone ran 89 octane? Top Tier only of course. Seems like a good half way point for daily driving.

I mostly run 89, and everything has been good enough for me over the first 30k miles. My overall mpg is 29.7.

I'll be honest, I think that I'm wasting money on it - unless you're really stressing the engine (a lot of full throttle, towing, high-temperature operation, etc.), the difference in octane isn't going to bump up your fuel economy enough to offset the cost. I drive with too light a foot to see a benefit in performance.

Random data point - the last tank I ran on 87 gave me 33.7 mpg. This was under pretty ideal conditions (a lot of sustained 60-65 mph highway, just cool enough to not need A/C). That's more than satisfactory in my book.

 

[Montana]

Its available in Central Texas, you just need to know where it's available. VP stations, and some Shell stations. VP also has 105 octane.

Is Conoco one of them as well?

 

[TxMike64]

I cannot confirm

Is Conoco one of them as well?

I cannot confirm. There are very few Conoco stations in my area, and if there were I don't usually use Conoco. My preference is 1. VP, 2. Shell, 3. Exxon/Mobile, 4. Texaco/Chevron. Not like it really matters though...

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