Ethanol-Free Gas (in Car) and MPG

RJM62

RJM62

Touchdown! Greaser!
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Geek on the Hill
I've posted about this in the past, and some of the experts told me it was impossible. So I took pictures this time.

The situation was simple: I needed gas on the way home from the dentist, but the first station I passed looked like an extremely low-volume station (translation: stale gas). The car's computer told me that I had another 40 miles of range, and I knew there was a busy Stewart's about 12 miles away, so I headed for Stewart's instead.

My car usually gets 40 - 44 MPG on rural highways with 89-octane corn-laced gas. But it gets close to 50 MPG on ethanol-free (which is always 91-octane or higher in New York). I've been told by many experts, both here and elsewhere, that the octane doesn't affect MPG and that the lack of ethanol couldn't possibly make that much difference.

Here are 19 miles worth of pictures that say otherwise. (I had the camera mounted to a chest strap for the first three pictures, so they're a bit fuzzy.)

1.jpg
2.jpg
3.jpg
4.jpg
The specifics:

2016 Kia Soul
1.6 naturally-aspirated engine
Manual transmission
Type of driving: Rural highway
Starting elevation: 1,562 feet ASL
Destination elevation: 1,507 feet ASL
Average OAT: 76F
Relative Humidity: 57%
Barometric Pressure: 29.83 in

I've sometimes sent pictures of the MPG readout to people who accused me of taking them immediately after filling up and coasting down a hill. We have no 19-mile-hills around here.

Three years of record-keeping with this car show an average 8 to 10 percent increase in MPG using 89-octane gas rather than 87, and an average 15 to 20 percent increase in MPG when using ethanol-free. The EPA and some engineers I've talked to say that's impossible. I guess I own a miracle car.

Rich
 
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Well, those who would tell you it's "impossible" don't understand modern engines or specificallhy the KiaPet you're driving.

While it is true you won't get more milage just because there's more octane, there's more a foot. Modern engines have knock sensors to keep the engine from damage from too low octane fuel. The Kia is notorious for having a rather agressive one. There's a recall on this. Even when the engine is functioning normally too low of an octane fuel can decrease the mileage due to the knock sensor.

As for Ethanol, there shouldn't be any surprise. Ethanol has about two-thirds the energy density per volume (e.g., GALLONS) as gasoline,

And by the way. Ethanol actually INCREASES the octane rating.
 
I don't understand why anyone would say it's not possible.

If you own an older car that uses an open-loop or fixed timing system, then no, it won't matter. If, on the other hand, your ECU is smart enough to optimize the fuel mixture and timing, then I can see how it would make a difference. Newer vehicles with computer-controlled fuel injection, valve trains, ignition timing, combustion chamber sensing of detonation and preignition, all of that... I can't see how you could make a blanket statement of "it can't make a difference".

As for the lower MPG with ethanol... I have read (I don't know for sure, not an engineer or chemist) that ethanol has 10% less energy by volume (or maybe weight) than does gasoline. BUT -- there's only 10% ethanol in E10 unleaded, so you'd think that would only be a 1% difference... but maybe there's an aspect I am missing.

My truck (F150 EcoBoost) has a fairly "smart" control system, circa 2011. It can run on E10 85 octane, but it likes higher octane a lot better. I've been running 89 octane E10 most of the time for several years; it's cheap. I fed it non-ethanol 91 octane this weekend for a road trip. I'd usually get about 18-19 on the highway at 75. I got 20.3 on the way out. On the way back I stopped and topped off (2/3 tank) with 93 octane E10; I averaged got 20.7 on the way home. Mileage in town since then has been slightly higher than usual also. Not a big difference, you say? Maybe not numerically, but it's about 5% higher.
 
I've done a few tests where I would run a few tanks of 10% ethanol gas and then measure the mileage on the 2nd and 3rd tank.
Then I switched to ethanol free gas and again, measure the mpg on the 2nd and 3rd tank. I don't use the first tank after switching to reduce mixing of fuels as much as possible.

I consistently get 10% lower mpg on ethanol gas of the same octane rating (91). If the station where I buy the ethanol free were closer, I would use it all the time.
 
Yeah, I get a solid 1MPG increase in my '08 F-150 (which can run e85 but I never have). For my truck, as long as the price difference is $0.30 or less between e10 and e0, I'll choose the e0. The higher the ethanol content, the worse the fuel mileage.
 
The energy density is 2/3 lower by volume for ethanol compared to gasoline by E-fuel friendly numbers. E10, is just over 2% lower than E0 by those numbers.

In fact it's worse than 2/3. The table commonly use over-states Ethanols density and understates straight gas. The poster's numbers are believable perhaps with E85 (about 71%), but harder to believe on E10.
 
DaleB said:
If you own an older car that uses an open-loop or fixed timing system, then no, it won't matter.
Click to expand...

Properly tuned, it will still make a difference in the older vehicles. The problem is, very few people actually tune things to optimum performance. Most people get it to the point it is "good enough" then leave it alone.
 
mondtster said:
Properly tuned, it will still make a difference in the older vehicles. The problem is, very few people actually tune things to optimum performance. Most people get it to the point it is "good enough" then leave it alone.
Click to expand...
OK, let me be more specific: Unless the tuning changes to optimize performance for the specific fuel being used. Simply switching from low to high octane fuel and back again won't make a difference -- although switching from E0 to E10 or vice versa might.
 
I noticed a difference in my carb'd CBR600 between E10/15 and E0. Advantage E0.
 
My motorcycle (Vulcan 750) gets 44-45 mpg on 91 octane, 40 on 89 octane going back and forth to work. Both with alcohol.

Now that I can get the gas cap open again (alcohol problems), and have found a place that sells gas without alcohol, it’ll be interesting to see how that compares.
 
flyingron said:
Well, those who would tell you it's "impossible" don't understand modern engines or specificallhy the KiaPet you're driving.

While it is true you won't get more milage just because there's more octane, there's more a foot. Modern engines have knock sensors to keep the engine from damage from too low octane fuel. The Kia is notorious for having a rather agressive one. There's a recall on this. Even when the engine is functioning normally too low of an octane fuel can decrease the mileage due to the knock sensor.

As for Ethanol, there shouldn't be any surprise. Ethanol has about two-thirds the energy density per volume (e.g., GALLONS) as gasoline,

And by the way. Ethanol actually INCREASES the octane rating.
Click to expand...

I've explained the knock sensor aspect to many people, including engineers, who simply don't seem to get it. Especially living in as hilly a place as I do, the knock sensor would constantly be enriching the mixture and retarding the spark on 87-octane. It doesn't with 89. I can feel the difference. I can go up hills a full gear higher on 89 than 87 because the ECM doesn't weigh in and ruin my joy. Above 89 octane (using E10), however, I experience no MPG improvement (but slight performance improvement).

That's why I attribute nearly all of the MPG improvement when using E0 to the absence of ethanol. I always use 89, so that's my baseline; and using 91 E10 doesn't yield any statistically-significant MPG boost. But 91 E0 improves MPG so spectacularly that it defies math. To achieve even 10 percent improvement based solely on energy content, the ethanol would have to contain zero energy.

So I understand the mathematical arguments that say it's impossible. My car, however, does not.

By the way, I've experienced very similar results with every car I've owned for the past 10 years. The numbers are most striking with the Soul, but every other car has also gotten much better fuel economy using E0 than could be explained by math and physics.

Rich
 
@flyingron hit the nail on head.

Very possible and probable. Getting that much of a jump is a bit much I think, but other things can occur. Either way, E0 has more energy than ethanol per gallon, so that by itself = more MPG all else equal. Higher anti-knock index with an appropriate engine management system will also get more economy out of a gallon of fuel. So there you go.

However if you have an engine that can't take advantage of the higher octane, it will run worse and perform worse on higher octane. I first observed this back in college on my Suzuki Bandit 1200S. It was designed for 87. I put 91 on it to be "nice to the engine". A friend suggested I try 87 since that's what it was designed for. Idled better, more responsive, more power and torque. Advantage: 87.

Them engineers who come up with the specs had a reason.
 
flyingron said:
The energy density is 2/3 lower by volume for ethanol compared to gasoline by E-fuel friendly numbers. E10, is just over 2% lower than E0 by those numbers.

In fact it's worse than 2/3. The table commonly use over-states Ethanols density and understates straight gas. The poster's numbers are believable perhaps with E85 (about 71%), but harder to believe on E10.
Click to expand...

It certainly defies the math, especially since many octane-boosting additives other than ethanol are also low in energy. But as I said earlier, my car doesn't know that.

My old 2001 Saturn also got a huge boost on ethanol-free, which I actually pumped by accident the first time. That car regularly got 40 mpg mixed (which is mainly highway up here) on 89-octane E10, and jumped to 46 on ethanol-free 91-octane.

Rich
 
My F-150 is flex fuel and I tried E85 in it a few times, I don't remember what the exact MPG was but it was noticeably less and completely negated the savings from the lower price per gallon. I've got no doubt ethanol MPGs are lower, dunno why you'd expect otherwise. Maybe people just assume anything "green" is more efficient too?
 
My mpg drop in my suburban does not make e85 a good buy at all... city driving I’ve seen under 9mpg, wher e10 gets me 12... highway about high 12s or low 12s if lots of grade changes, e10 I can be 16-17 plus..

Our e0 is a lot more in MI so it would take a huge bump to do make it economical, so e10 it is...
 
My Harley will get 3-5mpg better on the high octane real gas versus cheap alcohol gas, but its over 70 cents more per gallon, so if temps are below 80, & I am riding a lot I just use cheap fuel, but in winter when not riding everyday I do put good stuff in it, or the hottest days I summer, to help keep engine from pinging, & even with 93 octane it may still ping, but less likely, just hard pulls in high gear even thought may be 70+mph
 
My wife's Lincoln has run rough for most of the last few years. I filled it with Ethanol free 92 Octane and it ran considerably smoother and cooler.

The difference isn't entirely the fuel. The ECU knows the engine is running on fuel with different knock characteristics and compensates for it.

I don't know if the mileage increased or not. Don't care.

p.s. That car is my (her) only gasoline engine car. I'm a Diesel doer...
 
DaleB said:
OK, let me be more specific: Unless the tuning changes to optimize performance for the specific fuel being used. Simply switching from low to high octane fuel and back again won't make a difference -- although switching from E0 to E10 or vice versa might.
Click to expand...
The tuning changes in every car made in the last couple of decades, at least to the point where the spark lead and AFM are controlled.
 
Kenny Phillips said:
The tuning changes in every car made in the last couple of decades, at least to the point where the spark lead and AFM are controlled.
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Try to keep up. Here is what I originally said:
DaleB said:
If you own an older car that uses an open-loop or fixed timing system, then no, it won't matter.
Click to expand...
I don't know how much plainer I can make that statement, but let me try.

IF you have an older vehicle that DOES NOT automatically adjust the timing, mixture, etc... AND you don't specifically re-tune your engine when switching between higher and lower octane fuel.

Have I adequately covered it now, or is there more obtuseness to be had?
 
DaleB said:
Try to keep up. Here is what I originally said:

I don't know how much plainer I can make that statement, but let me try.

IF you have an older vehicle that DOES NOT automatically adjust the timing, mixture, etc... AND you don't specifically re-tune your engine when switching between higher and lower octane fuel.

Have I adequately covered it now, or is there more obtuseness to be had?
Click to expand...

It's really not complicated. The car doesn't know what kind of gas you put in the tank. There's no magic label in fuel that tells the engine anything. But the ECM does know whether the fuel is detonating rather than burning smoothly. When that happens, it retards the timing and/or enriches the mixture (as well as downshifts in an automatic transmission car when that's the sensible thing to do), all of which reduce fuel economy.

If you do nothing more than drive in a manner that minimizes detonation, you'll get a significant boost in MPG.

Rich
 
DaleB said:
Try to keep up. Here is what I originally said:

I don't know how much plainer I can make that statement, but let me try.

IF you have an older vehicle that DOES NOT automatically adjust the timing, mixture, etc... AND you don't specifically re-tune your engine when switching between higher and lower octane fuel.

Have I adequately covered it now, or is there more obtuseness to be had?
Click to expand...
There aren't many of those cars around. That's what I'm saying—that you point is moot in today's world. One of the big four car magazines just did a test with different octane fuels, BTW, that was interesting, and there is a difference.
 
genna said:
Octane and mpg

https://www.caranddriver.com/review...onda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/
Click to expand...

Tests done on tracks only reflect results when driving on tracks. Dyno tests are more predictive if designed properly, but few of them duplicate results similar to those that will be obtained in mountainous terrain.

If I lived in a flat place, I probably would realize almost no MPG benefit from higher-octane fuel. Rapid acceleration and climbing hills are the two most common situations when a car's ECM will step in to stop detonation. I'm a gentle driver and don't accelerate rapidly unless I have to (for example, to merge onto a highway). Take away the hills, too, and I almost never would push the car hard enough that the ECM would need to intervene. If you're not driving in a manner likely to induce detonation to begin with, buying fuel with a higher anti-knock value is just wasted money.

Living in the mountains, on the other hand, provides constant reasons for the ECM to tame the knocking; so the higher-octane does make a difference -- to a point. Anything over 89 (except E0) makes little or no difference in MPG and only very slight improvement in performance under load.

A retired Saturn engineer once told me that in New York, 89-octane is actually slightly less energy dense than 87, and anything over 89 is even less energy-dense. The reasons have to do with the octane additives in the higher-octane fuels being even lower-energy than ethanol. The higher the octane, therefore, the less energy per gallon the gas contains (assuming E10 at all grades).

I have no way of knowing whether he knew what he was talking about, but it seems to make sense based on my own experiences. I get a big bump going from 87 to 89, but little or no improvement above 89 (unless it's E0).

Rich
 
^agreed. Even this test showed some difference. Even on models that do not require higher octane. For most people, the difference does not justify extra expense, but in some cases expense is justified. I think 10-15% Ethanol probably causes bigger economy drop for most, however.
 
I know a guy that has a unit that turns old oil or similar into a usable fuel he runs in some old arse Mercedes diesels... now that would be cool to have!
 
Huckster79 said:
I know a guy that has a unit that turns old oil or similar into a usable fuel he runs in some old arse Mercedes diesels... now that would be cool to have!
Click to expand...

I have a 1986 Mercedes 300D that runs on waste oil, auto trans oil and vegetable oil. I created a filter/heater system that thins the oil in order to lower the viscosity.
 
IK04 said:
I have a 1986 Mercedes 300D that runs on waste oil, auto trans oil and vegetable oil. I created a filter/heater system that thins the oil in order to lower the viscosity.
Click to expand...

One of these days....
 
It takes alot more alcohol to make the same power as gas.
This has nothing to do with octane.
Check out a race alcohol carb vs a race gas carb... The Alcohol has huge jets compared to gasoline.
Look at fuel mileage of E85 vs gas... The E85 burns way more and gets less mileage.
 
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