Premium (no ethanol) vs. E10

Bob Wilson's current thread on this may be helpful:
Why premium is wasted in a Prius | PriusChat

 

Bob has done a lot of research on this issue - you should probably repeat your question in that thread.

 

It is math, E10 gets some percentage less MPG than E0, usually 3% but you can test yourself.

E10 gallons * E10 price * 1.o3 = E0 gallons * E0 price

as an example 10.3* $3.01 = $31.003 versus 10 * $3.40 = $34.00

So with gas near me, it will cost $3 a tank to save 3/10 of a gallon with E0 and go the exact same distance.

But first you have to know how much better your car does on E0 premium, I suggest fuelly.com, so you do not have save records

 

OK I did *sort-of* answer the question on Bob's other thread, but let me make it generic:

US EPA says E1o is 3% less heating value, and EPA also says gasoline density variation (which corrleates with heating value) could be up to another 7% correction factor, for a grand total up to 1o% MPG total difference.

The lowest MPG case is E10 blended into a low density gasoline. The highest MPG case is E0 of a high density gasoline. So now you need to know the density difference between your 87 octane and Premium, to see if there is any theoretical advantage for the Premium. You could also guesstimate 5-10% better MPG and see if you are willing to pay for it.

Meanwhile I am trying to think up a floating ball simple test for gasoline density. Also keep in mind your vehicle may not actually *see* a benefit for better energy content fuel, but at least if only we knew what the heating content was, we could see if it matters.

 

Just noticed the thread and it is a good question. My testing showed all but three brands of premium had the same energy content as all brands of regular. I didn't find a 'crappy' brand of regular as they all looked the same. So let's do some partial fractions:

• 114,100 BTU/gal - regular unleaded gas, Gasoline gallon equivalent - Wikipedia, the free encyclopedia
• 76,100 BTU/gal - E100, Gasoline gallon equivalent - Wikipedia, the free encyclopedia
• 110,300 BTU/gal - E10, (90% * 114,100) + (10% * 76,100)

So you're looking at ~3.3% better mileage with straight premium.

Excellent question.

Bob Wilson

 

^^^I agree with Bob and this is exactly what Consumer Reports would say: no benefit for Premium over Regular.

However, energy content may matter, so some provisos:

• In your case there is potential 3% MPG benefit for Premium due to lack of ethanol in Premium
• Although there is no benefit for Premium over Regular, there is a potential benefit for gasoline which has higher energy content. The problem is you have no way to know that unless (1) energy content is posted somehow, or (2) you at least have to measure density and ethanol content, or (3) do some accurate test drive work like Bob is doing to see if you can observe a difference.
• Of course, even if you measure an energy content difference Premium vs. Regular on any given day, it could be different the next day if the station got new batches of fuel. Again this is why CR would say forget about it. But I would presume some stations may have fairly consistent quality, while others may not.

 

This was my assumption when I started my 2007 gasoline testing so when I found three brands were higher than the others, I went back and retested them after the initial survey. There was at least a 3-4 month interval as each test entails running the tank dry after just partially filling the tank with 5 gallons. Normally I'm running about 2-3 weeks per tank so it still takes a while to complete one survey of the locally available brands.

With the exception of Costco which was only tested once, I stayed with name-brand stations. Again thinking they would have a commitment to consistent product. Curiously I remember some skeptics saying 'all gasoline is the same' and that may be true in some areas. This is why is it critical to always identify the city where the gasoline is sold.

Nationally, there are five major petroleum districts as defined by the Energy Information Administration. They follow historical, WW-II boundaries so I'm not so sure they map to today's distribution. So I would simplify it to:

• Gulf Coast
• East Coast
• West Coast (may have two division, California and 'the rest')
• Upper Midwest
• Mountain West or high plains

In reality, I would like to see sales maps from the different refineries but this is probably getting too close to 'proprietary information.'

Bob Wilson

 

^^^yes it is a misnomer to say all gasolines are the same.
On a molecular level they are all wildly different.
But all the ICE engine cares about is octane so that's the spec.

 

Dear C4 member:
I learned about ethanol-free gas when I drove my Camry and used it to drive from one state to another. I got better mileage using this. I bought my Prius in July and decided to only use ethanol free gas, even though it required me to drive a little more to get it. Here in Florida, there aren't many stations that sell it. I pay more per gallon but I don't mind, as I usually "top it off" when I am in that general vicinity. I usually get somewhere between 50-60 mpg all the time-city or highway driving. I only use ethanol free.

You can find it via search engine to locate gas stations that carry it. For my trips, I plan ahead to find stations along the way and even call ahead to see if they are open on my travel days.

In auto ads, the dealers claim a certain mpg per car, and those stats are based on ethanol-free gas usage. They don't tell you this. In fact one of the sales people told me this wasn't a good idea. Boy, was he wrong! I will never use ethanol gas in my car. I also use 87 octane. No need for higher octane, you're wasting money.

 

You raise an interesting question Charlie: how does EPA quote MPG for cars?
It appears EPA uses a very high energy content test gasoline - E0 and I believe relatively high density gaso.
Normal gasoline at the pump could possibly be up to about 10% lower MPG compared to EPA's test fuel (paraphrasing from an old EPA report). However, EPA obviously knows how to adjust MPG data for energy content of the fuel, so I do not know if EPA makes this adjustment before announcing MPG figures.

>> I wish EPA would clarify what energy content gaso and alcohol content they are quoting for MPG.

PS- Gasoline energy content differences alone could explain why Consumer Reports sees 5 MPG less on a Prius (for example) assuming CR is filling up at a real-life pump in my area.

 

I have never, ever, seen 87 octane that doesn't contain ethanol. That's the topic of this thread...you need to buy the 92 octane to get E0. Where are you buying your gas?

 

Pure-gas.org gives a listing of ethnaol free stations. In my area I would have to drive an hour to find it. Even if I drove the 1-hour to find it, I may not buy it often because it is a minor band name that I do not trust the additive package. In my area, even Premium has 10% ethanol, so there is no E0 option. The OP lives in Canada which is different regulatory story.

 

If I wanted to buy no name gas, I could get gas that CLAIMS to be E0, instead I buy Shell that CLAIMS to have "up to 10% Ethanol". They look the same, so I have to ask myself do I trust a 'brand' I have never heard of or a monopoly as evil as Royal Dutch Shell?. I have no faith that the E0 is 0% ethanol, I have no faith that the E10 is not 5% or 15% ethanol.

In the end I buy what is popular as gas that sits is called 'bad gas' and I do not want gas that has been in the tank a couple weeks. I buy what is on my route, as gas I have to drive out of my way to get is making me use more gas, and I buy cheap gas, I want to reward lower prices with more volume. (more volume means fresher gas)

 

The energy difference of E10 85 vs E0 97 is VERY NEGLIGIBLE.

The octane rating specifies how hard it is for liquid fuel to ignite under pressure.

And the Prius ECU is programed to change the A/F (air to fuel) ratio to accommodate 10% ethanol.

My guess is this:

You will pay more by using E0-97 gas and get the same performance/milage as E10-85 gas. This is largely because your ECU will adapt to the ethanol blend.

 

...you are philosophically correct. However, you might be technically right or wrong about saying the Premium has negligible energy content difference, since there are normal variations in energy content, including ethnaol E10 3% debit. Premium E0 could have maybe about 10% more energy, or alternately Premium E0 could have -4% less energy. The consumer has no real option but to assume zero energy content difference, so that's what you are saying.

As Prius owners, however, we can plainly see that 50 MPG figure in our display every minute, and we can see more than anyone else that variables such as fuel energy can impact MPG. So we tend to be very sensitive to factors that could improve MPG. Eg; why can't I buy a E0 with higher energy 10% better MPG? Well the answer is EPA mandates a low energy content base gasoline plus E10 reformulated gasoline in my area. So then you need to ask: is that the correct eco-policy for today's vehilces?

 

There is a difference between Economic Policy and Environmental/Ecological Policy. If you mean that if the EPA mandates in line with the most favorable Economic policy, then my answer is that the mandates are unfavorable.

However.. If the question is if the EPA mandates are the best for the Environment, then the mandates in tune and favorable.

Periphery nations are now undergoing rapid industrialization. This means that countries like India and China are beginning to demand more and more fossil fuels. Since out oil supply is already running out, the stress on the market from near infinite demand will eventually make oil unaffordable. In order to ease the transition the EPA has decided to mandate a percentage of ethanol in fuels.

I think that we need to move in the direction to biofuels and in the meantime sacrifice economic policy in favor for a smoother transition to renewable energy.

That and I get my waste vegetable oil for free from a Mexican restaurant and a Chinese Restaurant. I'm just collecting the oil right now until I finish my Mercedes E300 mod.

So is the EPA Mandate correct for today's vehicles?

Yes: It forces the big cats (oil cats) to loose weight, it forces mechanical entering advancements (Flex Fuel ECUs), it prepares the market for a not too distant biofuel future, guarantees less NOx emissions, and keeps tree huggers like us happy.

Is the EPA Mandate correct for our economy?

Maybe: They give us lower MPG's, we waste our money in performance robbing catalytic converters, gas prices increase due to extra eco taxes, they ground our cars if we blow too much green house gases, etc. BUT: They are preparing us for a future where oil will be unaffordable.

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Excellent post Bob.

However, in Oregon premium (92 PON) fuel has roughly the same ethanol content as regular (87 PON). This means the energy content variance is negligible between regular and premium in Oregon and Washington.

FYI- Mid-grade here (89 PON) is merely a mixture of 60% regular and 40% premium. A frugal person can often get mid-grade fuel cheaper by pumping premium first and then pumping regular. The break even point at today's prices is about $0.10/gallon for each step up in fuel grade. Any higher, and you save money by mixing yourself.