Pure Gas ( No Ethanol ) experiment

I won't get into MPGe, as I regard that as a farce in the first place. Miles/kWh (or Wh/km ) is my electric metric.

As for E0 vs E10 energy content ratios, and even E0 vs Itself, there is considerable variation depending on source. Here are some samples [bolding added], pick your favorite, or bring your own:

Alternative Fuels Data Center –Fuel Properties Comparison
"1 gallon of E10 has 96.7% if the energy of one gallon of gasoline. [3]"

Energy density - Wikipedia
Gasohol E10: 33.18 MJ/L
Gasoline (petrol) 34.2 MJ/L --> ratio = 0.970

https://www.concawe.eu/wp-content/uploads/2017/01/rpt_13-13-2014-00668-01-e.pdf
"For a 10% v/v ethanol/gasoline blend (commonly called ‘E10’), the volumetric FC should increase by 3.5% and the mass FC should increase by 4.2%. "

Energy content of fuels - Appropedia: The sustainability wiki
Gasohol (10% ethanol + 90% gasoline) 31.2 MJ/L
87 Octane Gasoline 3322.0 MJ/L --> ratio = 0.975

https://www.eia.gov/totalenergy/data/monthly/pdf/sec13_4.pdf
Until 1992, Approximate Heat Content of Motor Gasoline (Finished), excluding oxygenates, was 5.254 Million BTU per barrel. Since then, this table includes fuel ethanol, MTBE, and other oxygenates blended in. Current heat value: 5.054 M BTU/barrel, a 3.8% reduction from old value.

Alternative Fuels Data Center: Fuel Properties Comparison
"Property Fuels Gasoline/E10
Gasoline Gallon Equivalent [4] 97% - 100%
Energy Content (lower heating value) 112,114 - 116,090 Btu/gal (g)
Energy Content (higher heating value) 120,388 - 124,340 Btu/gal (g)"
Note that the spread from lowest low to highest higher is more than 10%.

 

Is that increase between ethanol free tanks, or to your fuel economy on E10?
If the latter, you are comparing winter E10 to summer E0. Summer blend has more energy than winter.

 

This is mpg from the first ethanol-free fill up , which included partial tank of Regular gas, to now the 3rd Ethanol free fill up.2.5 mpg improvement with a 10 gallon refill, 25 extra miles for $5, not an efficient choice

 

Specially if just the annual switch to summer blend played a part in the improvement.

I have experimented with higher octane gas in a car designed for it, and the pump price for midgrade and premium was just too high. The fuel economy increase wasn't enough to keep the price per mile from going up.

 

About 20% higher price on Ethanol free gas at gas station near us. Not worth for my car, but I do get them for my lawn mower.

 

Wow!

They really charge you for that stuff up there!!!

 

That indicates 6.25% increase in MPG, 87 octane ethanol-free(E0) over 87 octane 10% ethanol blend concoction (E10). After a decade of my five cars' records, showing 8%, 8%, 7%-8%, 7%, & 5% better MPG with 87 octane E0 over 87 octane E10, you are plunk in the middle of my data..... & way above the extra 1.8%(E0/E10) data quoted by ETC(SS). ETC(SS) accused me of lying, altho he has already been caught fudging ethanol blend efficiency with his incorrect 1.8% energy difference, which the "ethanol in gasoline industry" has also used in the past.
..... & there is a difference between 1.8% & 3%.

 

This increase in fuel economy is with regular part-time job driving. My wife idles in parking lots between grocery store deliveries. It makes me curious what the mpg could be, if I could spend an entire tank of gas feather-footing but we need the fuel-sipping car to do her job. Cheers.

 

I've seen $2.00 more a gallon for ethanol free on a sign once in NC.

No, it doesn't.
It indicates a 6.25% increase between E10 winter blend and E0 summer blend. I've just seen a 5.6% increase over the same time period with the only change in the RFG E10 here being in the seasonal blends.

There are also other possible variables. Changes in weather, driving habits, and traffic will have an influence.

 

Absolutely concur, but I also cited my source and (curiously) nobody has yet given me a decent explanation for why dot.gov uses the numbers that I cited for their GGE/GEG numbers, unless like the MPGe, they use "fuzzy math" for purposes beyond pure science.

As interesting and entertaining as it is to use anecdotal stories from people who drive cars that are notorious for having inaccurate MPG displays, there should be a repeatable real-world reason that cars allegedly get 8%, 8%, 7%-8%, 7%, & 5% better MPG with 87 octane E0 over 87 octane E10, to repeat the line.

I've been driving Priuses since 2010.
I always do just about the same thing, which is to drive until DTE=0 and then start looking for a gas station.
I put as close to 10.0 gallons as I can because I always hand calculate my real-world mileage (currently 50-ish) using real math.
I do not do this because I like to get into silly debates with the petroleum temperance movement, but because one of the first signs that a car with >100,000 miles is starting to lose a step or two around the bags is that MPG figures will decrease.
This might indicate that something is happening with either the suck, squeeze, bang, or blow -or- something else like bagged tires, dragging a foot, etc.

I've never seen as much as a 2MPG increase when I burn a bag of non-hooched gas - and I WOULD NOTICE that.
The real MPG delta is probably closer to 1, which is close to being lost in the statistical noise.
Even if I were politically motivated enough to "notice" a full 2-MPG delta, that's a lot closer to the 3-percent number discussed earlier than it is to 8%, 8%, 7%-8%, 7%, & 5% better MPG with 87 octane E0 over 87 octane E10.

So....that's my math, and I showed all of my work.
If that makes me a "liar" then so be it.

I don't like it when people bag on Priuses for being unreliable, because they're most decidedly not.

People ripping on hooched gas?
Well.
YMMV.....

 

Since I always use long term (years & decades) averages, I assumed George W. was using long term average. Possibly, George W. was NOT using long term average. Most certainly, George W. has experience with 87 octane E0, ONLY for the last 3 tanks of 87 octane E0. The first tank, had residual 87 octane E10 in the tank & the following tanks with even less percentage of 87 octane E10.

 

Looked up pure-gas.org YOU HAVE TWO stations with 87 octane E0 in San Antonio (with less-than-hurting prices?). I have to go a long ways for 87 octane E0 & longer still to get less-than-soaking prices!

 

It isn't 'lying' when he provided a reference supporting it, even it it was different than the many other references I find.

There is a lot of variation, and many different published figures, for the energy content of the underlying gasoline. I believe that is where the 1.8% vs 3% difference comes from.

 

I'm editorially fascinated, lol.

 

I hear what you are saying. My readings are taken based on actual usage over the short term, since discovering this thread.

I calculated the mpg based upon odometer at re-fill, not the Prius was guesstimating. My 40 mpg are not typical with norming city driving, but have become typical with hours of parking-lot idling. Since going to the Ethanol-Free, the parking lot idle mpg has increased almost to the point where it is similar to regular city stop-and-go use.

 

With Unleaded Regular @ $2.49, compared to 87 Ethanol Free @ $3.00, the extra 25 miles per tank isn't worth the additional $5 in cost.

 

He stated before you posted that it was a difference over 3 fills. The switch between seasonal blends happens on May 1st. Unless they have heavy use on the car, the comparison has winter and summer blends as a variable.

A really quick search gave 1.7% difference in energy content between winter and summer gasoline blends. So we have variables in play before ethanol even gets added or not.

 

A 20% price bump, for swapping 10% ethanol for the same amount of gas? That makes sense if you perceive ethanol in gas as a 10% detriment. Which sounds about right.

 

So just to be clear your methodology is flawed AND you are damaging your Prius.

Methodology: You should run it however much you want and then FILL the tank to cut off. Next tank do the same. Calculate the mileage based on miles driven against fuel used for fill up. The way you are doing it now assumes the DTE=0 always occurs at the same point. THEN you look for a station. The total driven distance is most assuredly not the same. Maybe it washes out in the noise after 100k but it's not controlled the way you are measuring it now. Another concern is that odometers are notoriously inaccurate. So unless you have calculated the inaccuracy the reported mileage is also off. True it will be off for whatever blend you use but it will be off.

Damage: You should NEVER EVER EVER run a tank to "empty." The fuel pump sits in the tank and is cooled by the gas. So when you are down at DTE=0 your fuel pump is not being cooled. In addition any contaminants in the tank will settle to the bottom. You really don't want those in the fuel system.

 

Do you have evidence for this? Most readers here have found otherwise. And past class action lawsuits for warranty fraud, going after car makers with allegedly overreading odometers, have pretty much abolished the errors in that direction. I received the legal notices on two past cars of different brands, neither of which actually had the alleged behavior. But the makers still provided a 2% warranty extension for miles as part of their settlements.

Sorry, but DTE initially at 0 miles and 1.9 gallons left in the tank, is most definitely not "empty." And the fuel inlet is always at the bottom of tank, so it should be dealing with whatever debris settles there all the time, not just when the fuel level gets low.

And PriusChat's Resident 'Mr. Curious Engineer', Bob Wilson, intentionally ran his first two Prii completely out of fuel more than 50 times as part of his many technical and fuel tests (completely draining one fuel before loading a different variety). and reported having no fuel pump failures whatsoever. If he had no trouble actually running dry that many times, than others such as ETC(SS) who fill up with about 2 gallons remaining should be home free.

This sort of frequent low-fuel scare-mongering from newbies, not backed up by real world examples but even running counter to a significant amount of first-hand experience here, is getting tiring. The real issue of running low fuel is not fuel system failure. Rather, it is the common human error of forgetting to refill in time and getting stranded, or in getting caught in unexpected circumstances and being unable to get fuel when needed.