MPG loss with 10% ethanol--- 2

[blacksmith37]

Theoretically there should be a 3% loss of MPG when going from gasoline to 10% ethanol. I have recorded every tankful MPG for 115,000 miles. A few yrs ago our rural was required to add 10% ethanol (to buy corn belt votes), so I have 70,000 of MPG with real gasoline and 65,000 miles with 10% ethanol. ( Same driver, same driving pattern, modern state -of -art fuel inj 5.6L Nissan V8). By inspection (have not mathmatically averaged data) it looks like a change from 16.8 MPG to 15.2 MPG, or about >10% loss due to ethanol.
Is there a reason why 10%ethanol would reduce MPG by more than 3% ?

 

[ornerynorsk]

70,000 + 65,000 = 115,000 ?????? Why, there's your loss and then some!

(sorry, couldn't resist)

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[blacksmith37]

As a norski curmudgeon myself, I am so embarassed by my arithmetic.
Tire pressure has always been "high"; 45 to 60 psig.
Can anyone suggest an easy to use (for a computer illiterate) statistical software. Real averages and std deviations could make me honest.
The only way ethanol even starts to look "green" is if the corn field work ,plowing etc, is done with solar power tractors; I haven't seen any working TX fields.

 

[blacksmith37]

IRStuff; In the old days there were 4 gasoline blends : high and low altitude, summer and winter. Today a refinery may make a dozen blends, as many legislators are now chemical engineers and define fuel requirements in local municipalities.
Old guy story : Oil corps used to monitor each others gasoline, Amoco would have meetings to decide if they should match (say Shell) in the Denver regeion because Shell was 0.2 octane higher than Amoco in that region.They worried a lot about "octane giveaway" like that.

 

[dicer]

I agree Dgallup, along with other not so apparent things as well.
Along with 10% alcohol, in the gasoline supplys, what percentage is the water emulsion, that will be displacing more gasoline, upsetting tune etc. I would say that is the major contributor to a variance in what a proper heat value calculation is and the actual measured MPG or power output. If this ethanol is so wonderful as a motor fuel and does all these nice things advertized how come the major airlines aren't using it?

 

[patprimmer]

Very small amount of water may be dissolved in the alcohol, but I never saw enough to separate out or form an emulsion. There will not be enough water absorbed to displace anywhere near 7% of fuel.

Aircraft have to travel long distances without refuel and weight is much more critical, so it is the same reasons behind WW11 aircraft not using alcohol vs top alcohol cars using it, ie mpg and consequential fuel load is more important in an aircraft.

Regards
Pat
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[Tmoose]

Maybe one of those analyzers that access the OBD II port and can report real time mpg would provide some useful info

 

[DigitalGT]

Tmoose,

The computers that plug into the OBDII port and report fuel consumption are only as good as the information they are provided. I have one called the ScanGauge II and it does a reasonable job of reporting mileage. It requires very deliberate refueling in order to correctly report to the unit what the car has just burned for fuel. Keep in mind these things only look at injector pulse width and fuel rail pressure (if available) along with the number of cylinders and do rough estimates of consumption based on what you tell it the engine it just burned (aka how much fuel was in the most recent fill up). If you don't fill up the tank every time and you don't do it the same way, or for that matter at the same pump, the numbers get skewed. Most of the ones also only have 1/10th of a gallon resolution. So you can't tell it you pumped 1.05 gallons, you have to tell it you pumped 1.1

If the vehicle has a non-return style fuel system where the ECU varies voltage to the fuel pump to keep the rail pressure at a desired value AND the scan gauge can't read fuel rail pressure (such as in my case) the numbers will be all over the place. Even though the gauge can read pulse width, if the ECU commands a high rail pressure during WOT and a lower one for part throttle duty the gauge gets left in the dark and is only really able to report an accurate average based on the previous tank's worth of driving.

They're nifty gadgets and I've used mine several times to diagnose problems. The built in DTC scanner it worth it alone. But I wouldn't use one and quote it's findings as empirical data. If anything I would only trust one to show me an overall trend over several tanks of fuel.

 

[patprimmer]

If you know your fuel pressure and you know it's stable, pulse rate should be a fair indicator of instantaneous fuel use, but is fairly useless at calculating broad usage averages. total amount added to the tank vs mileage covered over a long period of time is still the best way, It would be better if the variable being measured was swapped around at regular but long intervals, say like once every month, or once every ten tank fulls to eliminate a variable that might have changed at the same time the fuel changed by coincidence.

Regards
Pat
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[Lou Scannon]

Apropos WWII aircraft engines, some did use alcohol injection as an additive, in a surgical manner when it was needed most, "wartime emergency power", was one of the appellations, I believe. The Germans were onto this as well as the US, IIRC. Not sure about the Brits.

 

[patprimmer]

The Brits also used water/alcohol injection as a detonation suppressant, not as a fuel. I think the main reason for the alcohol was as antifreeze.

Regards
Pat
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[Lou Scannon]

quite right on both counts, same with the Yanks and the Jerries! I understand that there are some subtle advantages of alcohol vs straight H2O as a detonation suppressant (in terms of net power), but I'm far from an expert on the topic.

 

[dicer]

Reason old piston aircraft can't and won't use it is corrosive issues.And same as the modern aircraft below.

Reason any modern aircraft won't use it is because, of the lack of power or the increase in the amount of fuel needed to get that power.

And the reason it is used for our the motoring publics cars is, it makes our cars use more fuel. ie reduces the MPG.

 

[patprimmer]

Your not paranoid if they really are out to get you.

Regards
Pat
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[dicer]

Not at all paranoid, just check out the pump prices. It is reality.

 

[drwebb]

The airlines are looking at biodiesel for their renewables strategy, and flight tests have been conducted to establish feasibility running 1 of twin engine craft on blends.

10 years ago when I was in the fuel additive game, EPA only required 'testing' of additives that contained elements other than C, H, O, (or N?). So Ethanol and MTBE were not regulated as additives, although I'm pretty sure they got scrutinized for emissions control compatibility.

An Excel spreadsheet is about the easiest way to handle averages, standard deviations, and plotting the data as well that might be useful for spotting trends that may be significant.

 

[jmw]

Shame the guys at CRU can't use Excel... but maybe that's why they think the planet is cooking off and why we have to have biodiesel in the first place (despite the data coming in showing biodiesel is less good than fossil fuel).

JMW

http://www.ViscoAnalyser.com

 

[patprimmer]

I do check pump prices and buy the cheapest I have confidence in re suitable octane and cleanliness.

If it is E10, I calculate the value for money at 3% extra fuel consumption. It seems to work OK generally. Pricing mainly favours E10 here by a small margin.

I don't do accurate MPG checks, I simply zero the trip metre at every refill and get a feeling for distance travelled vs gauge movement and distance to empty and how much it takes to refill. Typically range is reduced a few miles on E10, but not so much compared to variations due to manner of use. Highway cruising is the only reasonably consistent manner of use as it is constantly at 110kph 99% of the time due to speed limits.

Corrosion is not normally an issue for E10. It certainly is an issue for E85 or methanol blends or 100% ethanol or methanol fuels unless the system is designed to handle it.

Fuel flow capacity is not normally an issue for E10 It can be an issue for E85 or straight alcohol fuels.

Tune correction for E10 is not normally an issue for E10, although how accurately that is handled might impact on fuel economy to give a different result to the 3& expected. It is a major issue for E85 or straight alcohol fuels unless the system is designed for it.

Fuel weight to cover a specified distance is greater for alcohol or alcohol blends. The more the alcohol in the blend and the lower the molecular weight of the alcohol (presuming only one OH group per molecule) the heavier the fuel load.

Aircraft will always be more concerned with weight of fuel to distance covered and with possible engine failure from using the wrong fuel where alternatives are available and there is a potential for confusion. If someone refuels a car from the wrong bowser, it might stop and cause some lost time and inconvenience. If an aircraft is refuelled with the wrong fuel. it might cause a crash. It ain't exactly rocket science and frankly I wonder why it needs this much explaining to someone qualified to be here.

Regards
Pat
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[NickJ67]

Returning to the OPs question, I'd like to throw another thought into the ring:

As E10 has stochiometric ratio of 14.1:1 rather than the 14.7:1 of petrol, in an engine fed by carburetor or open loop injection, changing fuels will cause it to run a bit lean.

Obviously modern engines (including the OPs) have closed loop control and will self-correct based on the signal from the O2 sensor. However, as ethanol also contains O2, could it be that this is throwing the correction off and actually leading to over-correction, causing the engine to run slightly rich and thus use a bit more fuel than expected?

Seems to me that given the fairly large sample mileages here 7% should be well outside the noise band. I would also tend to think that a nice big, low stressed engine like that will be barely getting into its stride at these kind of mileages - even to the extent that it quite likely used more fuel in the first 20 - 30k or so as it was still completing its "freeing-off". I know that I'm getting better mileage figures from my 230k mile Audi TDI than I was at 115k when I got it.

As an owner of other, older, petrol powered vehicles I'm not appreciating the other problems caused by ethanol addition such as failing hoses, loosened deposits leading to (repeated) blockages, O-ring and seal issues, diaphragm failures and so on. People are also reporting strange happenings on vehicles left standing for 2 or 3 months (winter layup) possibly caused by separation. Here in the UK we are only at 5% addition so far with 10% threatened.

Regards

Nick

 

[patprimmer]

The O2 sensor measures FREE oxygen in the exhaust and will not double count the oxygen already combined with the carbon or hydrogen.

Regards
Pat
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[Hotrodrobert]

I deal with performance street cars in North Carolina, USA. The E10 is a problem to any hoses, diaphrams, etc. We constantly have to replace hoses, fuel pumps, carburetor accelerator pumps, and fuel inlet control valves. Water and corrosion is a small problem, more so in the fuel tank of cars that sit.
For performance, a richer mixture is necessary because of the alcohol.
I also build very high performance engines just for E85. The fuel system MUST be built for the alcohol with proper hoses, pumps that can flow enough-you need at least 60 percent more flow, etc.
The higher octane of the E85 allows higher compression, boost, etc. to make much more power. You cannot EVER go back to gasoline without major modifications. Carburetors need major modifications.
Many vehicles have "Flex Fuel" which passes the fuel going to the engine through a sensor that changes the programming for the amount of alcohol it detects. These engines have larger injectors, etc. than non flexfuel engines.
Talk by the politicians is they want E20 now.