91 Octane w/Arco or 87 Octane with Chevron and other "name brand" fuel?

If you feel better paying more for premium , go for it , even though Toyota
Says you don't need to

 

One could almost imagine that this detergent-versus-that additive might make a statistically measurable difference in how your car operates over 450,000 miles, but the 87-89-91-93 octane question has been asked and answered.
A lot!

If changing from 87 to 93 Octane increased the mileage by 10-percent...or even 5????
The oil company's would have more TV commercials out there than GEICO and Progressive screaming about this "benefit" and calling people (like me) deniers of this new-found wealth of automotive efficiency.

Instead?
There are NO adds.
None.

That's because if you go on TV and tell people that you will get 50-percent more mileage with a "tornado intake" or a molecular fuel scrambler and you're a "Sham-Wow"-sized company, then they pretty much leave you alone because your adds have more caveats than a government statement about the ACA.
However (comma!!!!!)
If you're BP....or Exxon and you say that there is a measurable mileage benefit to using higher-octane fuel then you have to prove it or the Justice department will be all over you like a hobo on a ham sandwich!

Just look at the Prius community.
There are people tie wrapping pipe insulation to their cars, over-inflating their tires, and drafting off of trucks just to get a few extra miles to the gallon.
If the greedy oil companies thought that they could get away with claiming that their product would even net you ONE MPG extra, don't you think that they would at least tell you about it????
Instead?
No Ads.
Why?
No mileage benefit.

If you put 93 in a Prius????
You won't hurt anything but your wallet.
You won't help anything but your friendly neighborhood oil company.

Good Luck!

 

^^^what has sort of happened over the last 10-15 years, is the auto companies have made engine technology consistent with Regular grade Octane for the most part. Therefore the era of marketing special Premiums has gone away for the most part. I used to like Amoco Clear Ultimate Premium...that was good stuff IMHO. Now we don't even have Amoco any more, let alone their clear Premium.

 

When my 2000 Corolla got into later years, its Check Engine Light got sensitive to gasolines and octanes as such:
Arco - 87 & 89; light on
"No name" brands - 87 & 89: light on
Brand names (Chevron, 76, Shell, etc) - 87: light on
Brand names -89: light off

The results seemed pretty consistent throughout gas stations in LA and San Diego of a given brand and octane, so I concluded that different brands really are different. So for the last few years of Corolla ownership, I stuck with 89 octane brand names, except in emergencies. (After which it generally took a tank or so for the light to go back off.)

For the Prius, I've so far been using 87 octane brand name fuels. I figure that it probably doesn't need the octane push that the old Corolla seemed to, but also concerned whether the difference I'd experienced in brand behavior could point to gunkier vs. cleaner gas? do not know, but after all those check engine lights it's at least psychologically hard to pump some of the "Brand X'es" into the new car. ;-)

 

In my 2008 Honda fit, during cold starts in the morning below 60 degrees, it always took 1 less crank before firing up when using premium over regular; unless I counted incorrectly ever time...it seems to - in at least that case - help the engine start up smoother.

I also have two friends with a second generation Camry Hybrid. One who uses premium and the other regular. Again, subjectively (and recognizing other factors can be in effect), the premium user has a smoother ICE startup every time.

 

Well actually you are not only wasting your money but you are paying more for less BTU's per gallon. Premium gas has slightly less energy due to the anti knock additives. So many people do not understand what premium gas is formulated for. Premium fuel is only needed in high compression engines, reason being the additives are there to deter detonation. These additives actually retard ignition of the flame front that occurs when the fuel air mixture is compressed. In higher compression engines/ high performance engines detonation occurs with the use of regular gas. This is to say the mixture ignites prematurely before top dead center is reached and thus you get engine knock. If you don't have a high compression engine, the additives in premium do you no good at all. In fact the additives actually reduce the amount of energy available as compared to regular which actually has more pure gasoline in a gallon.

I agree with the others that say this subject has been beat to death! If your owners manual doesn't call for premium due to having a high compression engine then you are wasting your money and probably in terms of freshness of the gas in the stations tanks, since most people use regular I would suspect that the regular is fresher than the premium due to turnover.

 

^^^OK but what antiknock additives? There are none anymore ...used to be tetra-ethyl-lead.

 

Here are some Antiknock agent - Wikipedia, the free encyclopedia

 

...but none are used today (at least in USA) because the metallic ones would poison the 3-way catalyst in catalytic converter. WIKI mentions toluene and isooctane but those are just normal gasoline constituents.

 

It seems that many people say that you get no better mpg with 91 octane. I bought my first tank of 91 octane a few weeks back. because someone I work with was challenging to race their focus, and I thought I wanted any extra power I could get. I was supprised to find that my mpg has increased quiet a bit.my recent mpg has been about 52 mpg, this tank with over 400 miles is 60.4 on the MFD which is usually off less than 1 mpg. that is a large increase. Here in oregon we have E10 fuel I am not sure if this is why but it seems to large of an increase to ignore. the temp has come up some. but not enough to reflect the mpg increase. So I will be doing a little comparison. BTW I get all my gas at costco.

I understand toyota says use 87 or higher, I think that means that all 87 octaine gas is safe for the car and it should run properly.

 

I thought 91 would give me the same mpg as 87 until I did it. my mpg came up about 9 mpg. I was shocked. same driving, same psi in tires, temp just a little warmer. my car is getting much better mpg I guess it is the placebo effect. I see you also have a prius c, have you ever compaired 91 to 87 in your prius c? Here in oregon we have E10 so I guess it could be that. I must confess I am not sure but I will be using more 91 and see if my mpg this summer is better than last summer. the difference in cost was 20 cents if I remember correctly.

 

FUEL Additive in US used to make premium anti knock properties desired! Quote from the Economist.

"Another key additive that blenders stir into their brew is ethanol. That is done these days primarily to boost the fuel’s octane rating. A higher octane rating allows an engine to use a compression ratio of, say, 12-to-one instead of a more usual ten-to-one. The greater the compression, the higher the temperature within the combustion chamber. And the higher the temperature, the greater the thermal efficiency and power produced. In a nutshell, high-compression engines designed for performance need high-octane petrol.

Though ethanol has less energy per gallon than petrol, it has a considerably higher research octane number (RON)—around 108 to premium’s 97. It should be noted that this is not the octane rating seen on the pump in America. The RON figure results from a laboratory test done using a special engine with a variable compression ratio."

ETHANOL is considered an additive to guard against knocking and it has less energy per gallon as compared to gasoline!

 

To make your evidence more credible, you could do a full A-B-A test. Meaning, 87 one tank, 91 one tank and then 87 again. The third trial is to better isolate 91 as the sole reason for the change in fuel economy. Otherwise, it could be warmer temperatures as you say. Also I've read that some areas offer Premium with no ethanol. All other grades are E10. That could easily explain the increase in fuel economy.


iPhone ?

 

My thought is this can possibly be explained by a higher energy content of the higher octane Premium.

• the maximum MPG difference I would expect is 10% so you seem a little high.
• You are not guaranteed more energy content in Premium, it is just a possible variation

The 10% max MPG difference I would expect would be between an E10/lower density gaso vs. an E0/higher density fuel. 3% of the difference is due to ethanol and 7% is due to possible variation in the gasoline itself. And PS- others have made this similar observation that you have made.

But regular gasoline E10 contains 10% ethanol as does most premiums are E10 in USA...so ethanol is not generally being used as a lower energy, high-octane booster to make Premium. Ethanol is just like all the other stuff in gasoline, some of the compounds are low energy and high octance, some are high energy and high octane and they mix it all up and get an average octane rating.

Yes it is 100% possible to have a recipe for premium that is lower energy, higher octane. For exanple, E85 is lower energy, higher octane. But generally speaking, the refinery is probably going to put more stuff like toluene in the Premium (which WikiPedia mentions is antiknock at 0.87 density - that's a whopper with respect to energy content).

 

Please go BACK to the station where you got that tank of "premium" and look to be sure that it is not E0 (ethanol free). That is the ONLY thing in the gas that would account for that much of a change in mileage. The difference in OCTANE alone will NOT do it in the engine they you (we) have.
It just won't.

I had a similar increase last week on a 120 mile trip I went on.
The 60 miles there yielded about 53 MPG on the display.
The 60 miles coming back said something like 64.
The roads are pretty flat here and there wasn't much wind.
I have no idea why the difference........but mine was all on the SAME FUEL IN THE TANK.

 

Will you just STOP with the "higher energy content of higher octane Premium", PLEASE.

That phrase is misleading and mostly just plain wrong.

And it pretty much doesn't make any difference what you say farther down in the message; when you lead with that, it sets the (misleading) tone for the whole post.

 

Regular Versus Premium Gasoline

 

One more point to consider. If you buy top tier you can be fairly confident that it does has detergent / additives because its certified. If you buy non-top tier it may or may not be equivilent. Being certified top-tier costs money, and some brands may well meet the same spec but not think its worth it to pay for the certification. For example, I believe Arco, QT, and Costco all claim to add similar additives to keep fuel system clean, but they are not top tier certified. They may well be just as good as top tier, but there is no independent certification.

 

I am in violent agreement that Regular best for most of us. That's what I use all the time.
But I think there can be variations (until I get more data).

 

What exactly makes you think that the "top tier" stations are getting periodic inspections from an independent company to ensure that they continue to meet the standards ??

I have no evidence that they are NOT.......just an uneasy feeling, based on de-bunked marketing claims of the past.