Has filling up at a certain place made a difference?

I ran into something similar. I have had my car about 2 weeks and have driven it about 2000 miles. I was getting about 55 MPG without A/C and about 50 MPG with A/C. I had been using non-ethanol blend (straight gasoline 87 octane) from a small town station near my town. I was going on a longer trip last weekend and was near a big city WalMart with a Murphy Oil station that sells only ethanol E10 blend. The price was so good that I couldn't resist. I filled up with E10 89 octane. I had good luck with that station with my previous non-hybrid car. On my trip is computer said I got about 52 MPG without the A/C but I was running 72 MPH for most of the trip. On my way home I stopped at a small town WalMart Murphy Oil station that I had never been to before. This was still E10 ethanol blend 89 octane. With that tank full I was struggling to get above 48 MPG. With even small hills it was pushing into the PWR range on the HSI. The next fill up was back to my small town station with non-ethanol blend 87 octane. My next trip to work I pulled into work and the computer said I got 58.3 MPG.
So yes, I agree with other posts that I have read, the Prius likes good fuel and it may be worth trying to avoid the ethanol blends. So pick your gas stations wisely and avoid ones that you have found to give you problems like lower MPG.
Also, ethanol is often used to give higher octane numbers so using fuels with octane above 87 may actually reduce MPG. I suspect the Prius Atkinson engine may actually take advantage of the more rapid burn pattern of lower octane fuel.

 

I can see I have some more learning when it comes to the Prius, fuel economy, and which fuel to use.
The reason I say that is today I was near the Walmart/Murphy Oil station that I used to have good luck with for my non-hybrid car. The gas was $3.46/gal so I put in about 6.5 gal to top off the tank (net result of about 5% Ethanol). Per the trip computer the previous tank of 87 octane straight gasoline yielded 53.6 MPG (real fuel used calculated to be 52 MPG). Since topping off the tank with E10, 89 octane from Murphy oil I drove about 50 mile in mixed conditions ranging from city driving to stop and go highway, with multiple sudden stops due to the traffic. I also used the A/C for about 35 of the 50miles. When I got home the trip computer said 58.9 MPG, the highest I have gotten so far! I plan to drive until the tank is closer to empty and fill up again at the same station. I am really curious how the rest of this tank full goes and if a full tank of E10 does better or worse.

 

Fuel quality makes a huge difference. I experimented with all our local fuel brands / blends in my 2010 Prius.
I found my best fuel economy is from our local Cenex store that has blender pumps. Here in ND we do not have an ethanol mandate, so the same blender pump needs to sell a good ethanol free 87 octane gasoline stock, or your choice of E10 at 90 octane, plus E30 or E85 all using the same good quality 87 octane gasoline blended with the amount of ethanol you chose to use . My best fuel economy over many tanks and 4 years driving has been using Cenex E10. Last week we were in the middle of a 700 mile road trip, far from home and had the last bar blinking at us. No Cenex stations were close by, so we were forced to fill at an off brand station . I always reset trip A when refueling, so I have a constant "per tank" mpg record. This off brand rot gut must have been some really crappy gasoline stock, because my normal 54 mpg immediaqtly dropped to 46 mpg. I finally nursed it back to 47 by the time that tank was about gone, where we filled up with my usual Cenex E10, mpg immediatly returned to our normal 54 mpg.
It pays to play with different fuel brands / blends to see what your Prius "likes". In my case, going from the stuff my Prius "likes" to some really crappy gasoline , cost me 8 mpg.

 

The big difference I encountered was last summer a trip to Reno Nevada. I filled up, tank took 11 gallons, with
87 Regular Gas with No Ethanol. After 5 miles or so of driving I noticed an immediate increase of 3-5 mpg over
87 Reg. gas with 10% Ethanol....

 

For reasons I cannot explain with data, I get reliably good real MPGs with Citgo 87 octane (~52 mpg) versus other brands (non winter blends). This is over almost 3 years and 65k miles.

DROID BIONIC ? 2

 

If I get to a Road Ranger in Wisconsin they have a Regular pure!! no 10% Ethanol and it bumps my highway driving 10% .................. I wish Illinois had it by the way I was in Orlando this week gas at Hess was $3.31 back home in Northern Il it's $4.29.................. It's a big Screw job

 

I would worry much more about the quality of the 90% gasoline content that is in E10. 10% ethanol can only reduce the BTU content of your fuel by 3%, yet you claim a 10% difference. Where did the extra 7% economy drop come from ? It comes from the oil companies saving money by using a really crappy sub standard gasoline stock and spiking it with enough ethanol to meet the minimum 87 octane requirement.

The fuel I have used in my Prius for 4 years is from a Cenex blender pump that dispenses a good quality "pure" gasoline at 87 octane, or E10 at 90 octane made with the same quality gasoline with 10% ethanol added. over 4 years and 38,000 miles, Cenex E10 beats Cenex "Pure" 87 octane gasoline by a couple MPG, every time.

 

Ethanol will also absorb moisture which isn't going to help BTU content, but it does help add volume to their fuel tank and keep water out of their tank.... right into yours...

 

You will not see a measurable amount of water in any ethanol / gasoline blend, especially E10. Ethanol will only absorb at most .4-.5 % water before going into phase seperation. Thats 1/2 % of water in only the ethanol portion which is only 10% of the fuel mix. A tiny amount at the very most, and even there the oil co would be in trouble for very sloppy tank sanitation.

 

E10 is all they sell where I live. I try and use the top tier gas because they have better additives which over time keeps the injectors clean. Chevron is very good followed by Mobil and Shell

 

While all of that sounds plausible there are something things you are missing.
All tanks at gas stations must be vented to allow for expansion, contraction, and for air to take the place of fuel being removed. The air that is replacing the fuel has moisture equal to the dew point. Now since the fuel is stored underground it will be at the temperature of the ground, let's say 50degF. Now let's say its a humid day with a dew point of 75degF. As soon as the damp air hits the cold fuel the water will begin to condense on the surface just like a frosty mug. However being denser than gas it will begin to sink to the bottom. But instead of sinking it will instead bind to the Ethanol and detergents in the fuel. There is nothing to keep this from occurring right into phase separation you mentioned.
Now as far as oil companies getting in trouble with tank sanitation, who exactly would they get in trouble with?
Are samples of the fuel being taken from every gas station on a daily basis to make sure transportation, venting and storage issues aren't resulting in less than optimal fuel quality? Of course not.
As far as tank sanitation..... Do they pump the gas station tank dry into a HAZMAT tank before adding the new fuel? No, the contaminants get pumped out, into each and every one of our gas tanks.
And yes they may have filters here and there to try to filter out contaminants but how often do those filters get replaced? What is the level of filtering that they provide? Gasoline especially when blended with Ethanol contains detergents. Once contaminant bind with the detergents they pass through the filters. That's one of the reasons why motor oil gets dark in color. The detergents keep the contaminants in suspension and they pass through the oil filter. The problem with fuel & the detergents keeping the contaminants in suspension is that means the contaminants go right into the combustion chamber and change the burn pattern of the fuel. The bond between the contaminants and the detergents is also broken during the combustion process leaving the contaminants to deposit where the please. Luckily most of the contaminants are broken down or expelled during the exhaust cycle to hopefully be processed by the catalytic converter before being expelled into the air.
Also, is there anything that requires oil companies to throw away stall gas that has sat in storage, often the pipeline, for 3 months or more like we would expired milk? No.
Dry cell batteries, food and other perishable items come with expiration dates. Where is the expiration date for fuel?
Should gasoline be sent back to be re-refined after the "expiration" date has been reached.
Sorry fuel quality is a big deal and we as consumers are flying blind when it comes to having sufficient information about the quality of each tankful. Also cars like the Prius which are trying to sip fuel instead of drink it are going to be sensitive to the fuel being less than what it was designed to regulate and burn.

 

One local service station did NOT pump out the sludge sump in their fuel tanks on a regular basis. It destroyed the injectors in a late model diesel pickup. They paid the repair bill, over $4000 in this case, so yes, they have an incentive to keep their tanks clean.

 

Well putting in 89 is not giving you anything extra just cost more... I use 87 E10 (in may state I never seen straight gas :-( maybe exist but did not see any)

E10 has less energy per gallon so you will need more. Simple as that.

Also you need account for your driving technics are improving (well not sure if this is your first prius or not if not disregard).

Other than that I am not sure what is "quality" gasoline ... gasoline made in a very few places the only thing is different is the additives different "companies" adding (and that not much of a difference). Often area station getting the supply from the same supplier.

I maybe wrong but the only thing maybe an issue how long the gasoline stay at the station tanks.

 

Well oddly enough in Iowa E10 89 octane is typically the cheapest. To get 87 octane straight gas, without ethanol, it costs 10 cents extra. There is no E10 87 octane.

But face it, one of the biggest challenges with doing accurate testing of gas vs. MPG is it takes so long to use up a tank of gas with a Prius.

 

Not true at all, Gasoline is a blended mix of as many as 500 different hydrocarbon compounds, nothing at all pure about it. The quality of the crude oil and the skill and care of the fellows distilling gasoline can make a considerable difference in the energy content and combustability of the finished product. Ethanol is a single 99.9% pure compound that had almost no variability.
Remember that this variable mutts brew of hydrocarbon compounds comprises 90% of E10, while Ethanol is only 10% and very stable.
Of all the fuel blends I have tried in my Prius over the last 4 years, one local company that uses a high quality 87 octane gasoline stock that they blend with 10% Ethanol to make their very good 90 octane E10, produces the best MPG of any ethanol blend or so called pure gas, in my Prius. The tank of really rotten gasoline, also E10, I got on a 700 mile road trip recently, caused an immediate 8 mpg drop in fuel Economy in my Prius, which it gained back 460 miles later with the next tank of good quality E10

Like I said, Ethanol is a single compound , all the same. The gasoline portion of E10, however can vary a great deal. Too many oil co's in the E mandate states use cheap, crappy quality gasoline stock that they blend enough ethanol into to meet the minimum 87 octane standard, then happily blame the mpg loss on Ethanol.

Also consider that an engine does not produce a given amount of power / economy based on BTU's of heat energy alone, it's heat converted to cylinder pressure that pushes the pistons and makes the power. The burn and knock qualitys of fuel can have a dramatic effect on an engines ability to turn BTU's into cylinder pressure to produce power and economy.

The theory that less BTU's in the fuel means equally less power and economy, would only work if a gasoline engine was 100% efficent at turning BTU's to power. The fact is that most gasoline engines are only a little more than 30% efficient at turning fuel into power. A little over 1/3 becomes power, 1/3 is waste heat in the exhaust and 1/3 is waste heat through the engine cooling system. The quality, the ability of the fuel to burn rapidly and efficiently while resisting detonation knock, while producing maximum cylinder pressure, can skew the percentage converted to power or waste heat by quite a few %.

 

I am not sure what is the question the usa has about 150 refinery there several state which has ONLY 1 operational and about 15 states have NONE including mine New York.

So my point was/is that gasoline is not locally baked bread with great variety. Yes there are regions with multiple suppliers but the chances are that any locality is using the same whole sale refinery.

Some has extensively tested whether or not higher octane gasoline produces any higher mpg and if I recall the answer was NO.

And there is a long thread about different blend of EXX gasoline I recall somewhere in the E52 was the cut off point where the Prius computer could compensate, but did not worth it economically to do so ... E85 was not cheap enough.

I have a fuel storage are close where I live I have seen once four different oil-company trucks filled up from the same exact tower. So in theory refineries could make all kind of different stocks. But I do not think local markets (perhaps major metropolitan areas are exceptions) varies that much.

 

It depends so much on the quality of the 90% gasoline in E10. So many oil co's save a buck by blending low octane sub standard quality gasoline with ethanol to meet the 87 octane minimum standard of the lower altitude (non mountain) states. Some / most of that crap has a lower BTU content and poorer ability to burn efficiently.

In 4 years of experimenting with different fuels in my gen 3 Prius, I have found one local company that has blender pumps and good quality ethanol free gasoline, or your choice of 10%, 30% or 85 % ethanol blended into that same good 87 octane ethanol free gasoline. For those who do not have blender pumps or who live in an Ethanol mandate state that does not have ethanol free gasoline, this is how it works. The blender pump is connected to two fuel tanks, one full of good quality 87 octane ethanol free gasoline. The other tank is filled with E85, (15% gasoline / 85 % Ethanol.) This pump will fill your car with pure 87 octane, Ethanol free gasoline, or blend in 10% , 30% or 85% Ethanol into that same good Ethanol free gasoline to give a consistant quality gasoline / ethanol mix to make E0, E10 or E 30, E85.

My experiments using both the E0 ( no Ethanol) fuel from this company, or the E10 made with the same gasoline through the blender pump, blended with 10% Ethanol, to give an 89 octane E10 blend.
Over many tanks(4 years worth) of fuel, the 89 octane E10 has consistantly made right at 2 mpg better than the Ethanol free gas. I have no way of knowing if it is the 2 points higher octane or if the E10 just combusts better in a Prius ?
The fact that we have Ethanol free gasoline avalible and the fact that I can blend this same gasoline with 10% ethanol, gives me a golden oppertunity to compare the difference between pure gasoline and E10 using the exact same quality gasoline. In every case, the E10 of a known quality does a bit better on fuel economy in my Prius.

Joint research done by NDSU and a Minnesota university found much the same results. In a test of 6-8 ? late model cars, running on E0,(pure gasoline) or Ethanol blends, they found some models had the expected 3% drop in fuel economy, some had no difference, and some actually had a slight mpg increase using Ethanol blends, as does my Prius. Interesting that they found that those models that had a MPG increase on Ethanol blends, an E20 blend produced the best results.

 

Just a cursory read but you put 87 octane gas into a tank and get 89 octane gas out, is magic involved?
You get better mpg's with a mixture of ethanol and gasoline then pure gasoline, both 87 octane? As most have a 10% reduction of mpg's when blending ethanol into gasoline(10%) I am dubious

 

No magic involved at all, the Ethanol free gasoline is 87 octane. This same 87 0ctane gasoline when blended with 10% ethanol, produces an 89 octane blend as stated on the pump.( Ethanol is very high octane, (100+) and brings the number up quickly.

How could 10% Ethanol blended with a known quality gasoline, produce a 10% drop in fuel economy when it only drops the fuels BTU content by 3% ?
!00% Ethanol is listed as having 30% less BTU's than 100% gasoline, but E10 is only 10% Ethanol, 90% gasoline, so BTU's are reduced 3%.