Suprised with new car and E10

[Duffyjr]

First I'll explain why I'm surprised. With my 99 LeSabre I averaged around 30/35 miles less on a tank of E10 compared to E0 of city driving. I noticed this the first time I was in a situation where I had to use E10 so over the years I experimented and always got less miles per tank. I figured this out to be right at 2 mpg. At first E0 was only .20 more so it was cheaper to run E0. Then it jumped up to .25 more and was closer to breaking even but still used E0. Now it's .30 more and I have a different car (08 Lucerne) so when I got it four months ago I reset the average mpg and used E0, it settled in at 15.8 and didn't change much. This includes a couple 40 mile highway trips over the four months. I reset the average mpg and started using E10. I just ran thru my first tank and the average has been right at 15.7 of all city driving. If it stays like this I will keep using the E10 and save $5 every time I fill up.

One question I have is will it take a while for the computer to figure out I'm running a different fuel or since they both are 87 will it even matter.

 

[CharBaby]

I think there will be three schools of thought on this matter. Some will say "YES", it will take some time for your computer to learn this and others will say "NO", the computer should learn this during the first tank of gas. And 3rd, some will say that there should be NO DIFFERENCE since both E0 & E10 are both the same octane in your situation.

In my area, E0 is only in the higher octane range such as 90-91 octane and in other areas the octane may be even higher. I've seen the octane on E0 as high as 93-94 octane. Which are all in fact a higher octane than many/most engines will need according to their owner's manual. Most owner's manuals do state, "87 OCTANE OR HIGHER".

 

[skyactiv]

Forget octane and think of BTU's.

The energy content of one US gallon of E85 gas is 81,800 BTU, compared to 111,836 BTU for E10 gasoline.
Your gas mileage WILL suffer when using E85 vs E0 or E10.

A 2018 Dodge Grand Caravan with a 3.6L V6 is rated 17 city 25 highway on E10 gasoilne
It drops to 12 city 18 highway on E85.

 

[umungus1122]

Ouch! Looks like your '08 Lucerne gets about the same mpg as my truck! What do you get on the highway? I avg. 17-18 in summer in mostly less than 10 mile mixed driving on E10.

 

[Cujet]

BTU content of fuels is a factor that can't be ignored, for sure.

My 2011, F150, 3.5L ecoboost Super Crew gets about 1MPG or more with E0 90 octane, when compared to any octane E10 fuel. It's fastest with 93 octane. It's best MPG comes from E0.

Strangely, E0 driven really carefully can achieve over 21MPG. Something that just is not possible with Ethanol in the fuel, where it will hover around 17.5 or so. Quite simply, it does significantly better at low loads with non ethanol fuel.


Some of that may be computer calibration. Some may be related to BTU content. But there is no question that combustion chamber design and compression ratio, along with the knock sensor play a significant role.

With that in mind, every design is different and will give different results. Some engines are actually more efficient with regard to fuel BTU content and the resulting BSFC, with ethanol in the fuel.

 

[eljefino]

Originally Posted By: Cujet

Some of that may be computer calibration. Some may be related to BTU content. But there is no question that combustion chamber design and compression ratio, along with the knock sensor play a significant role.

With that in mind, every design is different and will give different results. Some engines are actually more efficient with regard to fuel BTU content and the resulting BSFC, with ethanol in the fuel.



Yup, if you can be more thermally efficient with higher octane and more timing/ compression, you make more power with less BTUs going in.

Be nifty if you could find some E0 high-test, I bet that would be amazing.

 

[Eddie]

A gallon of fuel with E10 has 4.6% less energy than E0. You should expect ~ 4.6% lower fuel mileage. Ed

 

[LotI]

I saw no difference over 10 tankfuls between E10(87octane) and E15(88octane). I ran a tank of 91octane E0 but saw no improvement in power so it's a waste in my GTI on a stock tune.

E15 is $0.05/gallon cheaper and VW is ok with it so that's what I run. It's entirely possible the higher octane lets the car advance the timing a smidge, lessening the BTU advantage. The ECU tests for knock at every startup, supposedly.

Keep in mind the BTU difference may be smaller as the blender can use "up to" 10% or 15% so the real alcohol content is lower.

 

[Duffyjr]

Originally Posted By: umungus1122
Ouch! Looks like your '08 Lucerne gets about the same mpg as my truck! What do you get on the highway? I avg. 17-18 in summer in mostly less than 10 mile mixed driving on E10.


I haven't had it out on the highway much but when I do the INST ECONOMY shows around 30 with E0. That 15.7 on E10 for the first tank was all city.

 

[raytseng]

it always depends on your actual drive.

no car is even close to btu efficient, so the plenty of ways where the btu energy difference gets swallowed up instead by fixed usage factors rather than proportional factors.

If the car is coasting downhill and idling or creeping, for example, the same volume of fuel is being burned, no matter if the fuel had a lot of btus or a little, all of it gets wasted, at the same flow rate.

All things being equal from just an energy perspective, you could assert the btu % difference as the maximum possible percentage difference, with real life difference more likely somewhere in between.

 

[Vuflanovsky]

I think that E10 might vary by state and production too depending on things like how much denaturant is in the gas. Supposedly, even in California where E0 is more a boutique dispensary idea, I've heard it said that E10 is typically more like E7 or E8 these days.

If ethanol has a third less energy than pure gasoline and the denaturant has about the same energy as pure gas, I can see how much denaturant is used coming into play if it gets over 2%. The government will give you a figure of 3% difference in mpg between E10 and E0 but I don't doubt that could vary between locales as an average figure.

 

[Cujet]

Originally Posted By: Eddie
A gallon of fuel with E10 has 4.6% less energy than E0. You should expect ~ 4.6% lower fuel mileage. Ed


That would be true, if all things were equal. They are not. The octane boost provided by ethanol, to bring the fuel to 87 octane R+M/2, may or may not be equally effective in different engines.

We tend to think of 87 as 87. But that's simply not true. As mentioned above compression ratio, combustion chamber design and even the air/fuel ratio, the way and when it's injected, and ignition timing all play a role in knock resistance.

It's entirely possible that E10 can in some engines, get exactly the same fuel economy, despite it's lower energy content.

 

[TiredTrucker]

Originally Posted By: Vuflanovsky
I think that E10 might vary by state and production too depending on things like how much denaturant is in the gas. Supposedly, even in California where E0 is more a boutique dispensary idea, I've heard it said that E10 is typically more like E7 or E8 these days.



E10 is usually no more than E8 anywhere. The max allowed with E10 is 10% and the fuel terminal does not want to get a bullseye painted on them by the state regulatory guys if they test a batch at the pump and it comes in at E11. Fines can be brutal. So they err on the low side. E15, same thing. Usually no more than E12 or E13. Even E85, the max I have ever seen is 80%. the E85 pumps in my area say between 51% and 82%.

 

[Vuflanovsky]

Originally Posted By: TiredTrucker
Originally Posted By: Vuflanovsky
I think that E10 might vary by state and production too depending on things like how much denaturant is in the gas. Supposedly, even in California where E0 is more a boutique dispensary idea, I've heard it said that E10 is typically more like E7 or E8 these days.



E10 is usually no more than E8 anywhere. The max allowed with E10 is 10% and the fuel terminal does not want to get a bullseye painted on them by the state regulatory guys if they test a batch at the pump and it comes in at E11. Fines can be brutal. So they err on the low side. E15, same thing. Usually no more than E12 or E13. Even E85, the max I have ever seen is 80%. the E85 pumps in my area say between 51% and 82%.


Yeah, I don't doubt they err on the side of caution with regulations and fines. I wonder how much variability there is between states/regions with things like denaturant and the actual differences in product. I'm sure giving a range of percentages for E85 satisfies consumer law but I'd be interested in seeing if there's such a thing as a consistent difference in one area versus another.

 

[jhellwig]

Originally Posted By: TiredTrucker
Originally Posted By: Vuflanovsky
I think that E10 might vary by state and production too depending on things like how much denaturant is in the gas. Supposedly, even in California where E0 is more a boutique dispensary idea, I've heard it said that E10 is typically more like E7 or E8 these days.



E10 is usually no more than E8 anywhere. The max allowed with E10 is 10% and the fuel terminal does not want to get a bullseye painted on them by the state regulatory guys if they test a batch at the pump and it comes in at E11. Fines can be brutal. So they err on the low side. E15, same thing. Usually no more than E12 or E13. Even E85, the max I have ever seen is 80%. the E85 pumps in my area say between 51% and 82%.


E10 is blended at e10. The only time anyone cares about the difference allowed is when something goes wrong while loading it on the truck. Only then do we calculate to see if it is in spec. I don’t know about e15 or e85 as we don’t blend it at my terminals. No one is going to short the amount of ethanol in the fuel because they are paid to blend it.

 

[Duffyjr]

So I have been thru 3 full tanks of E10 now and my average is at 15.6 so it seems my Lucerne doesn't care whether I use E10 or E0 and gets the same milage.

This makes me dislike E10 a lot less.

 

[kschachn]

That's thermodynamically impossible, but if you say so.

 

[Duffyjr]

Originally Posted By: kschachn
That's thermodynamically impossible, but if you say so.


Just going by what the computer says and it's been all city miles so maybe the issue is with the gas itself. The E0 I was getting at a non TT station (Casey's) because it's only .30 more a gallon to where the Shell E0 is .40 more than E10. The E10 I have been using is Shell because I might as well use TT since the E10 is the same price as Casey's. I've heard stories of people having issues with Casey's gas but I figured they were just stories but maybe there is some truth to it.

So maybe a few more tanks and it may drop more but it's not as bad as the 2-3 mpg hit I was taking with my 99 LeSabre.

 

[StevieC]

Duffy you would need to drive the same pattern in order to truly compare. I have seen a slight mileage gain from E0 fuel over E10 but it's so close that it would be hard to measure over one tank. Now if you drove roughly the same for 1 month with both that would be a little more accurate.

 

[Duffyjr]

Originally Posted By: StevieC
Duffy you would need to drive the same pattern in order to truly compare. I have seen a slight mileage gain from E0 fuel over E10 but it's so close that it would be hard to measure over one tank. Now if you drove roughly the same for 1 month with both that would be a little more accurate.


I have. I bought the car in March and ran several tanks (5ish) of E0 and ended up at 15.7. But as I mentioned in my last post this was with Casey's gas. I just completed 3 full tanks of E10 and it's at 15.6, but this is with Shell, both 87. Not sure how big a role the Casey's vs Shell is playing here.

I know that all sorts or things can come into play here and I'm not trying to be exact or scientific I'm just observing for the sake of my wallet. The cost difference keeps increasing between E0 and E10 around here. I've pretty much settled on using E10 unless the milage takes a dive down into the 13 mpg area then it may become more cost effective to go back to E0.