Octane vs MPG, 87 vs 93, anyone compared?

[Ranch]

Partially answering OP's question; yes, you should see a slight difference in MPG and HP when changing between 87 and 93 octane gas; but no, I have not tested this myself with my Maverick.

What I can tell you is that when I had my Focus ST (same motor), yes there absolutely was a difference when running the two different octane levels. Through similarity, I would assume the same for the Maverick. The ST had a boost gauge on the dash (I am a firm believer the Maverick should have one from the factory too LOL), and you could tell on 87 that the car was not creating as much boost. This is a result of both a difference in ignition timing, but also the wastegate (NOT the blow-off valve, they are two different things) on the turbo opening sooner (this is electronically controlled by the ECU). I'd have to test it myself with my Maverick to get a concrete number, but in the ST it was typically a 1-2 MPG increase when running 93. It slightly offset the cost increase of running 93, but not completely.

Also, @Blkraven66 mentioned above on the Winter Blend gas. This is also true, if you live in a cold climate that switches between summer and winter gas, you'll notice a drop in MPG during the winter. On an old Ranger I had, the drop was only 2 or 3 MPG, the ST it was around 6 to 7 MPG. I'm noticing in the Maverick it seems to be around 3 or 4 MPG, but I'll give it the rest of the winter with more tanks to get a real definitive answer on what the drop actually is.

I can't buy 93 octane gas here in Sacramento, only 91 octane. So I would probably see 1 or less MPG gain with premium gas vs 87 octane. At 35 to 40 cents a gallon more for premium means using 87 octane is cheaper for me.

Owners manual says that using top tier 87 octane is ok so I'll probably use that for everyday use when I get my Maverick. When towing I think I'll switch to 91 octane for better performance.

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[matmondro]

I can't buy 93 octane gas here in Sacramento, only 91 octane. So I would probably see 1 or less MPG gain with premium gas vs 87 octane. At 35 to 40 cents a gallon more for premium means using 87 octane is cheaper for me.

Owners manual says that using top tier 87 octane is ok so I'll probably use that for everyday use when I get my Maverick. When towing I think I'll switch to 91 octane for better performance.

Agreed! When I'm going to be towing, I'll put 93 in it. But for now, 87 will do for just about everything. Some gas stations by our cottage up north have 90 octane no-ethanol Rec fuel, but it's almost double the cost of 87 LOL.

 

[GPSMan]

Is is legal to put ethanol free in your on-highway vehicle? In some states ethanol free is strictly for off-highway use.

 

[LSchicago]

For daily driving, the 20¢ per gallon difference isn’t worth it.
Most modern engines run just fine on 87 octane, you start to see a benefit with octane on higher output engines. Primarily in a track setting.

20 cents? It's $1 a gallon difference in my area from 87 to 93 premium.

 

[BlueSnake77]

Is is legal to put ethanol free in your on-highway vehicle? In some states ethanol free is strictly for off-highway use.

That doesn't make sense. why would ethanol free be for off-road use only? I was using non-ethanol gas in my Escape becuase a local gas station still sold it on 2 of thier pumps and was priced the same as thier 93 octane 10% gas. But after the whole Covid thing, the Non-ethanol has shot up in price so now it costs like 20to 30 cents more per gallon than 93 octane 10% ethanol for some reason.

 

[GPSMan]

That doesn't make sense. why would ethanol free be for off-road use only? I was using non-ethanol gas in my Escape becuase a local gas station still sold it on 2 of thier pumps and was priced the same as thier 93 octane 10% gas. But after the whole Covid thing, the Non-ethanol has shot up in price so now it costs like 20to 30 cents more per gallon than 93 octane 10% ethanol for some reason.

When I lived in Minnesota back in 2008 10% ethanol was mandatory for on highway use. The non-ethanol was strictly off-highway use. Emissions laws, etc.

In CA it's either illegal or just not available at retail, not sure which!

Ah ha. Just looked up California.
CA law does not specifically mandate ethanol use (I think because it is so far from the corn belt it could be difficult to procure enough at times.)

CA does mandate fuel contain X percent of oxygen molecules. Currently, there is no better economic choice for oxygen content than ethanol. So in a nut shell, all gasoline has 10% ethanol currently.
No exceptions for small engines.

 

[pgstick02]

Is is legal to put ethanol free in your on-highway vehicle? In some states ethanol free is strictly for off-highway use.

In PA it is not mandated and can readily find it at various stations but I can't speak for other states.

I only run Ethanol Free in my 1973 bug as it tends to run worse with ethanol. It's an older vehicle which was never designed for it. I notice a major performance dip with ethanol added fuels of the same octane rating. Most people now use it for older cars and small engines like mowers and other carbureted applications.

To answer the original poster.
Short n sweet Ford recommends it, that is what I will do.

I am with the crowd of it is a turbo engine 91 or better top tier fuel when possible "As noted in the manual". The computer would adjust for anything lower, causing no issue other than a performance handicap with no harm to the engine at 87 or greater. That was exactly how my last daily worked as well and had 6 years to test it. I did notice better mileage and performance, so I am just running on habit since it is the same situation.

Worse case I threw money away on higher octane in hopes of longevity to the engine and a cleaner burn and if Ethanol Free 91 was abundant at all stations I wouldn't mind the extra cost in the Maverick

Maverick manual snippet copied from Fords website: Fuel Quality - Selecting the Correct Fuel
Your vehicle operates on regular unleaded gasoline with a minimum pump (R+M)/2 octane rating of 87.
Some fuel stations, particularly those in high altitude areas, offer fuels posted as regular unleaded gasoline with an octane rating below 87. The use of these fuels could result in engine damage that will not be covered by the vehicle Warranty.
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.
Do not be concerned if the engine sometimes knocks lightly. However, if the engine knocks heavily while using fuel with the recommended octane rating, contact an authorized dealer to prevent any engine damage.
We recommend Top Tier detergent gasolines, where available to help minimize engine deposits and maintain optimal vehicle and engine performance.

 

[Mark S.]

... if they are both E-10 then there is not a significant difference.

Agreed!

There is a significant difference in fuel economy between regular & premium if the regular is E-10 & the premium is not...

That depends on how you define "significant." I saw no significant difference in my testing (all data posted at the link I provided), but others have claimed otherwise. I've seen some claim they get 28 mpg with E10 and 32 mpg with ethanol-free premium. I question data like this mainly on physics.

If we agree that there is no significant difference between regular and premium E10 fuels, then the only factor we have to control for in a comparison between E10 and non-ethanol premium is the ethanol. The most obvious difference between gasoline and ethanol is the energy content. Gasoline (both regular and premium, BTW) contains approximately 116,000 BTUs compared to ethanol's 76,000. Subtract one-tenth of the gasoline and you are left with .9 gals containing 104,400 BTUs. Subtract nine-tenths of the ethanol and you have .1 gals containing 7,600 BTUs. Combine the two remainders and you get .9 gal of gasoline (104,400 BTUs) with .1 gal of ethanol (7,600 BTUs) containing a total of 112,000 BTUs.

Now we can directly compare the energy content between E10 and non-ethanol premium. E10's 112,000 BTUs is 96% of the non-ethanol premium's 116,000, a 4% reduction. Therefore, if ethanol were the only factor you should see a 4% reduction in fuel economy with E10 compared to non-ethanol gasoline. 32 mpg minus 4% = 30.72 mpg. Whether or not you consider that difference to be "significant" is a matter of opinion. But based on physics alone, it's clear that other factors besides the fuel used are at play if someone reports a difference of 32 mpg vs 28 mpg between E10 and non-ethanol premium.

 

[GPSMan]

Yes.

Every University ON THE PLANET (Earth) says E10 = 3.5% lower energy and subsequent MPG.

Every Governmental testing agency says E10 contains 3.5% lower energy and subsequent MPG.

Every Fuel Manufacturer says E10 contains 3.5% lower energy and subsequent MPG.

That, ladies and gentlemen is consensus. That, ladies and gentlemen Is consensus because it is scientific fact.

Everything else is rounding error and placebo effect.

So to be fair, E10 needs to be priced 3.5% lower and traditionally it is.

 

[James K]

Hand computation on a single tank is not sufficient--there are too many variables. The only way to get an accurate comparison is over several tankfuls. The Owner's Manuals for Ford's EcoBoost Mustang and Bronco Sport say to get accurate hand measurements you should track miles over at least three tanks.

For what it's worth, I own a Bronco Sport with the 2.0L, so the drivetrain in my car is largely the same as that in the 2.0L Maverick. I tracked mileage by hand over several thousand miles of driving. Driving more miles averages the variables yielding more accurate comparisons. I compared regular and premium, and ECO and NORMAL driving modes. You can view the results in this thread over at the Bronco Sport forum. To answer OP's question: there was no significant difference in fuel economy between regular and premium gas.

I'd agree in the old days, when the computer didn't adjust timing, but have to politely disagree today on both Maverick and Bronco with EB 2.0. Premium fuel has long gotten a bad wrap because misunderstanding of ignition timing. EB motors change the timing according to the octane they sense, this then changes the HP and torques output and yes, with those changes, MPG is most likely going to change also.

 

[GPSMan]

Does EB have an "octane" sensor or "knock" sensor.

Not the same.
The former is proactive.
The later is reactive.

 

[James K]

Agreed!

That depends on how you define "significant." I saw no significant difference in my testing (all data posted at the link I provided), but others have claimed otherwise. I've seen some claim they get 28 mpg with E10 and 32 mpg with ethanol-free premium. I question data like this mainly on physics.

If we agree that there is no significant difference between regular and premium E10 fuels, then the only factor we have to control for in a comparison between E10 and non-ethanol premium is the ethanol. The most obvious difference between gasoline and ethanol is the energy content. Gasoline (both regular and premium, BTW) contains approximately 116,000 BTUs compared to ethanol's 76,000. Subtract one-tenth of the gasoline and you are left with .9 gals containing 104,400 BTUs. Subtract nine-tenths of the ethanol and you have .1 gals containing 7,600 BTUs. Combine the two remainders and you get .9 gal of gasoline (104,400 BTUs) with .1 gal of ethanol (7,600 BTUs) containing a total of 112,000 BTUs.

Now we can directly compare the energy content between E10 and non-ethanol premium. E10's 112,000 BTUs is 96% of the non-ethanol premium's 116,000, a 4% reduction. Therefore, if ethanol were the only factor you should see a 4% reduction in fuel economy with E10 compared to non-ethanol gasoline. 32 mpg minus 4% = 30.72 mpg. Whether or not you consider that difference to be "significant" is a matter of opinion. But based on physics alone, it's clear that other factors besides the fuel used are at play if someone reports a difference of 32 mpg vs 28 mpg between E10 and non-ethanol premium.

Who agrees there is no difference between regular and premium E10? Certainly not me nor would your ignition computer and we know what the Dyno would say. While laid out nicely, you didn't allow for real world variables. Can I assume you're in an engineering curriculum or recently graduated? 5Y doesn't only apply to problems but should a standard for all thought.

 

[Mark S.]

I'd agree in the old days, when the computer didn't adjust timing, but have to politely disagree today on both Maverick and Bronco with EB 2.0. Premium fuel has long gotten a bad wrap because misunderstanding of ignition timing. EB motors change the timing according to the octane they sense, this then changes the HP and torques output and yes, with those changes, MPG is most likely going to change also.

The PCM modifies timing to curb power output when the knock sensor fires. This indicates detonation is occurring, and the PCM will retard timing (and power output) to prevent it. But it only does this at high power demand. There's no advantage to changing timing at lower power demand when detonation is not occurring, otherwise the PCM would do so ALL the time, not just when using premium.

 

[voldemartian]

From my experience in my hybrid 91 octane got my from 38MPG to 42MPG so not nearly enough for me to care really. especially for the price difference. I didn't notice any performance boost either but I did notice that after two full tanks of 91 going back to 87 the truck dragged and got horrible mileage. like 29 mpg. It corrected after going through a full tank but my guess is that it was the computer trying to compensate for the different fuel but I'm not an engineer so I really don't know. I've been running 87 for the last couple thousand miles and I'm still getting 38-39 mpg.

 

[James K]

The PCM modifies timing to curb power output when the knock sensor fires. This indicates detonation is occurring, and the PCM will retard timing (and power output) to prevent it. But it only does this at high power demand. There's no advantage to changing timing at lower power demand when detonation is not occurring, otherwise the PCM would do so ALL the time, not just when using premium.

Good point, well reasoned, but still not sure its' accurate in real world. We don't operate only at the bottom of the motors capacity. While we can't take your deposition on your real world experience on this subject (you having a hybrid and all) I'd be happy to give mine.

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