Anyone used premium fuel????

orenji, a lot of detailed explanation on octane can be found at Ask.com and a lot of other internet sites.. You are very right in noting that using a too low octane rated fuel might harm an engine however there is NO power or mpg benefit gained from using a higher octane rated fuel than the owner's manual prescribes. I believe Dan is suggesting that delayed combustion in which an engine is not set up for might cause less than proper/planned ignition which might harm the engine over an extended use....please note he used "might cause..."
My question is Why use high test fuel if the manufacturer does not call for it in the owner's manual?
From Ask.com :
"Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power."
Most engines are designed and tuned to run efficiently on USA typical regular 87 octane.
One would probably do no harm to an engine if one uses "premium"...only unnecessary harm to one's pocketbook.
How would Dan's position of discouraging unneeded use of premium fuel harm the public ?
I don't understand.

 

The octane rating has no direct relationship to the energy content (BTU's) of the fuel. It could be said to contain more 'activation energy' but that only indicates exactly what an increase in octane rating does - allows the fuel to be compressed more before detonating, allowing a car that can take advantage of that to make more power. If the car is not tuned for that however, the fuel will provide no benefit. There are not any more btu's in Super vs. Regular. Now what else any given fuel is blended with may change that equation, but it's not directly related to the octane rating.

 

I was in total agreement with the Ask.com person until he/she said fuel efficiency is a misconception. I believe (I posted an old EPA article) it used to be true that EPA/SAE used energy content of test fuel to adjust MPG reading of test cars using test fuels. What I don't know if that same adjustment is still made by EPA/SAE. This would tend to suggest energy content does impact MPG.

It definitely true that premium is not guaranteed to have higher energy content, but it might have more energy content. I am not recommending premium, rather trying to undertsand how much variability is in fuel and the extent to which a Prius might see as much as 10% MPG difference due to fuel variability.

 

Now you are spreading misinformation.

What I wrote is no my theory, nor is it my thoughts. It is fact, and if you do your own research you too will see what I write has a lot of merit.

Using an octane higher than an engine is designed to run with is a waste of money, and gives false hopes to the driver that doing such a stupid thing is good.

If you understand what octane is, what it does, you too will see the error of using premium in a car that calls for just regular.

Octane slows down the combustion, effectively retarding it. This can be a great thing if the engine is designed to take advantage of those properties.

Using too high of an octane can cause incomplete combustion, that over time can cause faster engine wear, and cause unexploded fuel to combust later in the exhaust manifold, or catalytic converter, or muffler (BACK FIRE). Over time this can do severe damage to a car.

 

octane does not add power, does not improve performance. Higher octane gas ignites at higher levels, and accordingly better allows an engine to deal with heat by preventing pre-ignition (pre-ignition causes knocking or in the case of performance engines may cause piston or valve damage).
....so race gas is 113 octane - not to add power - but to allow performance cars to contend with the heat created by running high levels of power.

-so adding some boost juice will not hurt the car, but it really is not adding any power either.
In California heat, high octane helps control pinging better. I have seen it and believe it.

 

But there just is NOT. Sometimes they even add an "inhibitor" to achieve the higher octane......like tetraethyl lead.....that does not burn and has basically a ZERO energy content. Thus it is more likely that a higher octane fuel actually has less "energy content".

Now......if the regular has ethanol and the "premium" does not, that is a whole different discussion.......but it's about the energy content of ethanol, NOT about energy content versus octane.

 

...all I am saying: just as ethanol has lower energy content, the gasoline energy content also varies. So you have two variations: ethanol plus the base gasoline. For example, in winter they put lower energy content butanes in for example.

However, just as you mentioned E0 for example is one way to get higher energy content. I also believe EPA reformulated gasoline (what we have) is lower energy content (gasoline portion) than non-reformulated gasoline. Therefore I might see a pretty good double whammy energy content boost if I filled up with E0 outside of my EPA region -- whereas I have to drive an hour away to even get E0.

That leads to the next question: even if I learned how to buy higher energy content gasoline, I am not even sure the Prius cares about it. But I think the general correlatons (eg; for ethanol) do suggest energy content is a factor.

 

I'm going to keep it real simple, just like Toyota recommends.

Regular Gasoline...Top Tier Stations.

I don't think a higher octane will hurt. But I don't think it will help either.

I have some concerns, of consistently using a higher octane because the Prius engine is a Atkinson Cycled combustion engine. Which if my "Google University" degree is valid, combines all the strokes of regular Otto Cycled engine in just two revolutions of the Pistons. Seems to me, from what I've read the whole point of an Atkinson Cycled engine is to use less fuel, and create less combustion. (More Efficient-Less Power).

If the engine is cycled to operate with "less combustion" why would I want to use a higher octane that creates an explosion at a higher compression rate?

I don't know if that would hurt or help...but I'm just sticking with the "cheaper" octane Toyota recommends, and I'm going to be happy I don't own a vehicle where premium fuel is required.

 

If you turn to the last page of your owners manual, it states the following:
"Unleaded gasoline, Octane rating 87 (Research Octane Number 91) or higher.
If using Premium or Super gas rated at 91 was bad, TOYOTA would not be saying to go higher than 87. 87 is the lowest Octane to use. I will take what they say as they know their engines best.

 

Hum....so why does a 90 horsepower Fiat 500 motor require 91 Octane, as well as the Smart Car and Mini Cooper? These are certainly not high performance motors. Again if you look in your Toyota manual it states use 87 octane or higher. 87 Octane is the lowest Octane one should use.

 

You can go higher...but why?

And YES...Toyota knows their engines the best.
I spent a considerable amount of time in Prius Chat before the release of the then at the time "New" Gen 3 Prius. There was quite a lot of angst, and worry and waiting to find out what the recommended Grade Gasoline was for the newly arriving Prius.

The Toyota Prius team even got involved. The final word that came down...the new Prius runs on regular.

Can you go higher? Certainly. With gas additives, fuel injector cleaners and other products, PLUS owners like yourself that like to imagine a benefit of running higher octane, Toyota isn't going to design an engine that is going to self-destruct or explode if a tank or more of Mid-Grade or Premium gasoline is used.

But the recommended octane level is "regular" or 87....you can go higher..but why?

If "Premium" was the recommendation, then the wording would be "Use Premium"...

It's disingenuous and a misrepresentation to suggest that the recommendation from Toyota ISN'T regular. Because it is.

There are NUMEROUS threads bearing this out.

Here's one of many.

Why premium is wasted in a Prius | PriusChat

 

Because they are designed that way - the Fiat 1.4l for example has a compression ratio of 10.8:1.

Whether the engine is a 'performance' model or not has nothing to do with it - it all comes down to the design. Yes, performance engines are more likely to require premium because they are generally making more power for their size and there is some expectation they will be driven harder.

Anything higher than 87 in the Prius will just be emptying your wallet faster.

 

Marketing of a vehicle that will run on 87, and driving a vehicle in the real world on 87 are two different things. Manufactures need to design vehicles that will sell and a vehicle that does not need 91 octane is easier to sell. But in the real world, driving conditions and quality of gas can all take negative affects on an engine, that is why there are knock senors. However knock senors don't always function as they should. Which over many years will harm the engine. For the small cost difference I will continue to use 91 octane as I do on all my cars, and have never seen any negative affects from doing so, and have never had a fuel related part repair.

 

The difference is that, running 87 in a vehicle that requires 91 means that you are relying on the knock sensors all the time. In a vehicle designed for 87 running 91 you aren't using the knock sensors, and if you have knock, it's because something is wrong, in which case the small safety margin provided by 91 is no guarantee it will prevent any damage.

Premium is generally about .40/gallon more than regular - meaning for the average car, you're pouring hundreds of dollars of extra money into the fuel companies pockets every year for no benefit. Over the years that will pay for a lot of 'fuel related' repairs! (Not to mention those are extremely unusual in most modern vehicles - especially any type that could be related to fuel choice)

 

Yes, for their size, they absolutely ARE.
It is the compression that is important, not necessarily the "performance" but the two usually track together.

As in most contentious discussions, both sides are going overboard here.
It is perfectly OK to use a higher octane fuel once in a while.
One tank full will NOT cause any problems.......except for your wallet.

Continuing to use it ALL THE TIME is just stupid. It gains you nothing, costs you more and there is a tiny chance that it might actually cause some damage over time.

 

Total BS. You are just being dense and stubborn......which is absolutely your right, as long as you don't
try to convince others that it is somehow "right".

A new station opened here last week. A Race Trak, I think.
It has THREE nozzles on every pump.
One for Diesel, one for the normal 3 tier E10 grades and another for E0.
Regular = $3.40, Mid =3.60, Premium = 3.80, E0 =4.00.
Masters of marketing, I say.
Even though the E0 will have slightly more energy content, it certainly is NOT enough more to justify the extra $.60 a gallon.......but if paying more somehow makes you happy, that should suit you just great.

 

By what criteria would you say that? HP/displacement? Compression ratio? Just a random Internet comment?

Contrast those engines to other Otto cycle engines of similar displacement that recommend Regular.

 

#Freedomofchoice

 

Hey fellas

I always use 91 octane in my prius because the small motor can use the extra boost. However, in my 2012 nissan gtr, I use 89 octane because it's such a beast and doesn't need any octane boost. And it runs circles around every other car

 

Anyone used premium fuel????

Yup.
Every time I've ever owned a vehicle that requires it.
Sadly?
I'm a person of humble means, and so currently I only have an 06 Harley VRSCD that requires premium fuel.

Put Premium in a Prius?
It won't really hurt anything....but....why???