It doesn't.

 

Seeing so many drivers finding less mpg I called a couple of cohorts still in petroleum refineries and found that indeed the refineries are producing less energy gas by altering the recipes to get more production. Thats before diluting with ethanol.
With the disasterous drought in the midwest corn will be a premium and if ethanol is still required look for foods and gas toi get very expensive.
I estimate that gas is down to 110,ooo btu/lb from what used to be 113k.
Diluting wikth 10% ethanol kicks it down to about 107k and that will cost about 3 mpg easily. wselcome to the world of the socialist Democrat.

 

I filled up with premium (93 octane around here) and immediately noticed the car was running more smoothly. I'm at about 100 miles on the tank, and according tot he gauge have only used 1/4 tank. The past few tanks I'd be approaching 1/2 tank.

Maybe it's just me, but I think using premium (NO ethanol) is making a difference. We'll see...

 

Good experiment. Just out of curiosity would you share:
1. the brand of gasoline you are experimenting. Please don't change brands.
2. If TX is like most states they have to label the pumps with the statement saying how much ethanol MAY BE in the gasoline. Note its a limit, not a guaranteed amount and it does vary. What is the limit there?
For botgh regular and premium.
How are you going to be sure to refill to the same point each refill. No,you cannot use the dashboard gage.
Since you are much closer to the refineries that serve your area your result will interesting.

Thanks.

 

I'm curious about the composition of 91 vs 93 octane gas. Most stations around here offer 87,89,91 (with 89 being a blend done in the pump), and I'm curious if - given that presumably 91 is also a pump blend of 93 and 87 - there is any meaningful difference between "premium" 91 and "premium" 93. Hmm.

 

way way back in 1972 a movie star that I cant rember got a hold of a chevy impala and converted it to Natural Gas. you could breath the exhaust. Im sure the car didnt go as fast as gasoline, or get the gas mileage. but seriously I dont give a rats ---. If nascar can do it to there 100 thousand dollar car why the heck arnt we. That's early 70 if we switch then where would we as a country be? God only knows. There r gas station that r run by regular folks that make there own alcohol and put the require gas-chemicals in and then sell it to like a Co-op. We need to stop worrying about how the gasoline companies r going to screw us
today and start goggleing. The info is out there in book on you-tube. we can make alcohol out of grass clippings. I'm not a rep. or dem. I think their both corrupt. We r still free, well to a pt. LOL. My life isnt dependent on big oil, because I made the changes that I needed too.

P.s. I'm not saying that americans r dumb, but sometimes we show a serious lack of getting off our ----- and doing what's in our best interests.

 

Shell, fromt he same station I almost always buy from.

15% maximum ethanol, as per sticker on the pump. As far as I know, premium will never contain ANY ethanol.

I always fill to first cutoff, then give it two more squeezes, which consistently equal about 2/10 of a gallon total. I never fill the filler neck, even though you can get more than an extra gallon in there.

 

Just a quick update. Half a tank gone (93 octane from the same Shell I always buy), 174 miles on the trip, whereas at this point, at least recently, I'd normally only have about 150. Fillups have been happening at around 250-260 miles, so if the trend continues, I'll at least break even on the difference between regular and premium due to my increased fuel economy.

I should also add the car is running much better. Just more power, less stumbling.

 

Some premium grades contain ethanol, they have to post it up though.



By the way guys...

That sound you hear? It's steve's head exploding

 

Top Tier Brands will have ethanol in it. E15 is coming to a station near you but its voluntary if you use it. Car manufactures wont honor warranties because its voluntary and some stations owners wont carry it unless they promise they wont be held responsible for any problems. 1 out 5 cars failed the tests that should of passed. Luckily RFG summer gas cant have E15 but starting in Sept. that can change. Also they are trying to get wavers for no Ethanol gas but that is has not passed yet and its on a state to state basis and I believe 38 states have some form of wavers.

 

If that dont this will.
Part 1
Part 2

 

If the pump is labelledd premium will have ethanol. From a chemical stasndpoint, there's no reason why premium can't have ethaznol in the gasoline. Ethanol has enough antiknock to fit the requirement but in truth the mpg will suffer because the heat of combustion is lower.

 

Depending on the composition premium gas is ethanol free but can have ethanol in it. Aromatics and ethanol have similar gravity weights so they will mix but aromatics can hold water which ethanol will absorb and fall out of the gas called fuel separation. Since premium gas will have more aromatics then regular and sits in the tanks longer it has to have more stable ether's or higher alcohols like Isopropyl alcohol which solve that problem of fuel separation.

 

So in short, premium really is PREMIUM, and not just because of the octane rating?

I truly can tell a difference with regard to performance. There's one corner in particular that I hit every morning. It's one of my morning commute "I might not autocross anymore but that doesn't mean I can't practice technique" corners.

Anyway, it's a 4-2 downshift and I like to trailbrake a little just before the apex to scoot the tail around a hair. Blah blah blah, normally the engine will stumble and hesitate a little after the hard change down, even with the appropriate throttle blip (which is damn near impossible with the electronic throttle in this car). But lately it's smooth as glass! Power right on the exit with no hesitation.

 

Premium gas is really a premium product. There is more to it than just octane and as you can see your car runs better. Did your mpg go up too?

 

Adding fuel to rthe fire, though I'm retired I still have cohorts left in oil refineries and they say that the recipes for regular and premium are more different now than ever thanks to the huge increase in gasoline required to serve Americans and no additional refineries are being built thanks to the 'nanny' government we have now. Those recipes have less energy per pound than ever and it shows up as reduced ignition and less mpg properties. Because premium is a small portion of gasoline sales there hasn't been much effort to reduce premium qualities; thats about to change .
That drive for more gas with same refineries is compounded and assisted by the requirements for ethanol added to our gasolines. (wait'll the effects of the drought on cotton ergo ethanol production increases ethanol cost and foods bills at the grocery.) There are more efforts in place to reduce the energy of gasolines, premium included, in order to increase production.
For now you might try the mid level gasoline so you don't have to pay 40c per gallon more but get by on 20c. If things go the way that they seem to be headed you'll need that savings.
Hmmm, more gas of inferiior quality, increased costs at gas stations and groceries, promising stuff they can't possibly deliver, you might get the idea our present government trying to 'get' us.

PS anybody seen the new Ford Fiesta; carbon copy of Fit except its bigger.

 

30.4 MPG. Since there were other factors (lower temperatures, increased tire pressure), I went back to 87 octane this week, just to make sure. So last week was sort of a control in this experiment.

As an aside, I had to take one of my weedeaters in for repair. It was a fuel issue. The mechanic told me practically every small engine he's seen this summer has had issues related to ethanol, mostly water in the system, but also degraded lines, seals and gaskets. He recommended using the off the shelf premixed 2-cycle fuel, and premium for the lawnmower.

 

I only pay .24 cents more for premium. I agree regular has more energy per pound but most of it is lost due to knock and then you have ethanol. E 15 is voluntary so they will lower the price to get people to bit. The experts say 5 degrees of retard equals 1 percent loss in torque but there is 7-10 degrees of retard with regular so there is a lot more. After 5 degrees or retard efficiency drops at a higher rate. They have to raise the octane to meet the mpg quota and ethanol is not the answer. Ethanol Free Premium Coalition

I lost faith in what products they are selling. Bp got caught with their pants down and proved no quality control and also mixing regular with premium when 2.1 million gallons of unleaded fuel was contaminated and made it to 200 stations before the problem appeared. As long as my mpg is consistent I will continue to use premium BP.

 

Some really interesting info in this thread. Thanks!

And now for an update, after filling up with regular 87 octane last Wednesday... 225 miles with between an eighth and a quarter tank showing (which means I probably have about 30 more miles before the light comes on). If that plays out, then by the numbers premium is a better value PLUS makes the car run objectively better.

 

Gas quality plays a lot it mpg. I was going through my papers and found this http://www.pecj.or.jp/english/jcap/j...1-2_koseki.pdf.

The major reason is lower sulfur in premium. It can have between 90 ppm to 10 ppm. Lower ppm means better mpg. I thought because of RFG gas that it was the same sulfur content but its not true. My wife's Civic exhaust had a lot of deposits which I believe is from sulfur from regular gas. Bp ultimate had 10ppm for many years which is a big reason for even better mpg over the year for me.