My corn vs corn free gas comparison test

[johnboy]

Earlier I posted in the home improvement section under the chainsaw thread about the station near me with corn free gas.
I did a 15 tank comparison with my daily driver awhile back and the results were interesting.
Daily driver: 98 Mustang v6 5 speed-slow as fuck but faster than walking

Mods- cai, true duals with hi-flow cats and flowmasters, 8.8 with 3.27s and a Foxbody 5.0 throttle body modified to fit, sct tuner

The Foxbody swap was good for a couple of reasons. The factory throttle body had a reducer from cai, fox did not and it was 2mm bigger than aftermarket one.

I ran same 87 tune on both tests

My drive is 50 miles one way, roughly 85% highway speed.

My test was 5 tanks of corn 89 octane, then 5 tanks of corn free 89. Then 5 tanks of corn.

The corn averaged 24-28 mpg on both 5 test tanks, which is normal under those conditions. I used Exxon 89.

Corn free averaged 20-22 mpg.

I was somewhat disappointed with the results, same driving conditions, no a.c. use. Everything I have read about corn gas is that it knocks mpg down. I have two theories about this.

1. Maybe without realizing it, car performed better and I drove more aggressive.

2. The corn free gas didn't have all the cleaners and additives that the corn did.



Cliff notes- got worse mpg with corn free gas vs corn gas

Edit: I want to clarify when I said corn gas, I meant the ethanol blend e10 not e85, and the corn free is pure gas with no ethanol.

[Gasser64]

Thats cool and all, and we do appreciate the test and you doing your due diligence. But I think that this is something that is already well known.

[Strychnine]

Thats cool and all, and we do appreciate the test and you doing your due diligence. But I think that this is something that is already well known.

It's known that E85 gets better mileage? Really? i would LOVE for you to cite that.

Before you dig too deep a hole...

Ethanol has 76,100 BTU/gal
E85 has 81,800 BTU/gal
Gasoline has 116,090 BTU/gal

[johnboy]

Smegma, it's a well known fact that ethanol reduces gas mpg. I didn't do the test for anybody but me. So I shared. In my case ethanol gas was cheaper and better than the ethanol free gas that I have access to.

Thanks for playing.

[Broncojohnny]

I'll bet the corn gas actually has a higher octane than 89 and your car needs the octane for whatever reason. My 95 GT would get terrible gas mileage on anything other than 93 octane super.

Put in 2/3 of a tank of 93 octane and fill the rest with E85 and see what it does.

[johnboy]

Broncojohnny, interesting theory. I have a 08 f150 regular cab short bed with the 4.6. Not exactly a powerhouse. I run a edge programmer on it. It has 3 tunes. #1 just changes shift points. #2 is a tow program and #3 is a 93 octane.. If I run #1 mpg is about 16, #3 I get 18-19 with. So I run the 93 for the mileage and the bonus is it runs alot better. This is also the reason I daily the stang.

The non-ethanol gas by me has 87, 89, and 93. I might need to play around with the octanes and types of gas on the stang.

[Strychnine]

When you say corn gas are you talking E85 or the standard E10 (or less) we get at most pumps?

[johnboy]

I edited it earlier. I meant the e10 not e85. Sorry about the confusion, I wasn't even thinking about e85 when I posted. And I just edited it again.

Edit: I was hoping that you would chime in. I know you posted a long time ago that all oil was processed the same and when it was branded the company would add their mix to it. That's why I did my test, to see if I could get better mileage with the pure gas. I did 5 tanks each to help with any variable such as traffic, wrecks etc. I drove stang to work and home and that was it. Drove truck any other time. I was surprised about the pure gas doing so bad.

[Gasser64]

It's known that E85 gets better mileage? Really? i would LOVE for you to cite that.

Before you dig too deep a hole...

You really, really need to learn to read. Like really really.

"Cliff notes- got worse mpg with corn free gas vs corn gas"

[BradM]

You really, really need to learn to read. Like really really.

"Cliff notes- got worse mpg with corn free gas vs corn gas"

You need to shut the fuck up.

[Strychnine]

You really, really need to learn to read. Like really really.

"Cliff notes- got worse mpg with corn free gas vs corn gas"

So i have a few calls to make this morning before i can come back to respond to the other guys here, but in the mean time would you mind fleshing that out a bit and explaining your logic on this one? I'd really like a glimpse into your mind on this one.

[Strychnine]

This one's for Blake. It's a slow day over here so pardon the length

tl;dr - Think 'tolerance stackup' in machining - when the stars align you can get a load of shit. $5 says it was all driver/environmental... and none of this actually explains why you saw E10 gains, but it might not be as fuel related as you think.


There are too many variables and your results are just too far out of acceptable ranges to determine anything here, but it's still fun to think about.

Post up the individual tank averages?

It's good that you did 5 tanks on each, but what happens if you throw out the first 2 tanks on each fuel and just look at the last 3? Your system is never going to be totally dry, so in those first couple tanks there's going to be leftovers and blending.

How long did it take you to run through each tank? (long enough to average out weather changes?) A 30* temp change can affect mpg by 4% just due to tire inflation.



This next part may be a bit too much but it's just to make a point:
When it comes to fuel consumption, anything outside of a dyno lab setting is going to have a pretty wide margin of error. Road testing is more to monitor trends and large differences. This gets fuzzy, but using the average of your averages you got 26 mpg on E10 and 21 mpg on E0 - 19% reduction on E0. In practice though that 19% loss is not all fuel related. A portion of that is due to every other variable in the world (weather, traffic, payload, how much coffee you had that morning, etc).

I'm working through something similar right now. This is all HD diesel stuff, but we're dealing with two different heating value fuels. To get a baseline I put a logger on a truck and let it work for a month, fueling from the same tank and same nozzle every time. We knew that this truck/driver had one route that he had to repeat a few times over that period so we went through the data and pulled out only those trip logs. Taking 3 drive cycles and laying the vehicle speed, engine speed, engine torque, and altitude on top of each other you can see these are probably as close to identical runs as we can get - similar to you doing this on the same drive to work every day.

Even with the most repeatable real world test we could muster up, and using injector fueling rates straight from the ECM (no hand calcs) there was still up to a 6% variance in fuel economy.

If you had a 6% variance due to duty cycle and 4% variance due to tire pressure, you've just accounted for half of that 19% right there and those have nothing to do with fuel... but none of that explains your numbers going the wrong way.

[Strychnine]

I'll bet the corn gas actually has a higher octane than 89 and your car needs the octane for whatever reason. My 95 GT would get terrible gas mileage on anything other than 93 octane super

Any guesses on why?
Is a '98 smart enough to tune on the fly? I thought those years didn't have knock sensors (only the DOHC Cobra stuff did) so there wouldn't be timing adjustments or anything else going on.

[Strychnine]

Thats cool and all, and we do appreciate the test and you doing your due diligence. But I think that this is something that is already well known.

I'm running low on enlightenment lately, so if you could chime in...



I did a journal search to see what's out there on increased mpg in engines that are not optimized for E10, and I only found two studies, neither of which you've ever read.


1.) American Coalition for Ethanol, Fuel Economy Study, 2005 - This study claimed to show an increase in mpg, but if you actually read it you'll find this:

The three vehicles averaged 1.5% lower mileage with E10, 2.2% lower mileage with E20, 5.1% lower mileage with E30, and miles per gallon actually increased by an average of 1.7% when using E10AK made with the specially denatured ethanol.

The noted increase was using an ethanol fuel that had soy diesel and isopentane blended in.


2.) “The Effect of Fuel on the Emissions of Vehicles over a Wide Range of Temperatures,” Journal of the Air & Waste Management Association 43 (July 1998) - This is the only study I can find that shows any increase with E10. All cars tested were old pieces of shit, and even the authors of the study couldn't figure out why this happened (they were mainly studying emissions and this was byproduct info)

Fuel Economy
The results of the fuel economy were unexpected, with an almost equal number of the test averages showing an increase in fuel economy with the use of E10. The expectation was that there would be a loss of fuel economy due to the decrease in energy of the E10 fuel. The results of the fuel economy are given in Table 5. The highest increase was 12.4 %, from the ’92 Corsica with E10. The largest decrease in fuel economy was with the ’84 Caprice, with a decrease of 17.8% in fuel economy with the use of E10. All other increase and decreases were less than 10%. The average increase in fuel economy with E10 was 5%, while the average decrease was 3.5%.

Fuel Economy, MPG
94 Aspire: -0.6%
89 Celebrity: +2.4 %
88 Voyager: +2.0 %
84 Buick: +1.7 %
84 Caprice: -17.8 %
87 Blazer: +6.5 %
92 Corsica: +12.4 %
91 Dodge Truck: +6.7 %
86 Monte Carlo: -3.1 %
77 Mustang: +2.6 %
84 Ford Ranger: -5.8%

[BradM]

You really, really need to learn to read. Like really really.

"Cliff notes- got worse mpg with corn free gas vs corn gas"

https://en.m.wikipedia.org/wiki/Dunning–Kruger_effect

This is your assigned reading.