There are a few fallacies with the last post too. It would take several pages to explain in detail, so I'll just leave it at that for now.

The bottom line is that pump premium fuel has no downside, unless one needs to pinch pennies. Guessing wrongly in the opposite direction can have huge and much more costly consequences.

I wouldn't dream of putting anything less than premium in my supercharged Corvette, my blown+nitrous dragboat, or my Harley. We put regular in the Jeep, the Nissan, and the lawnmower.

 

This is from the Consumer Energy Center and the link below is from Scientific America

REGULAR VERSUS PREMIUM GASOLINE
Regular Gasoline Has As Much Merit As Premium Gasoline
"Put a tiger in your tank," says a classic advertising tagline. In today's motoring world, what kind of fuel grade will have the power to place a beast in your gas tank?

The answer, according to experts who study fuel efficiency in detail, is both regular and premium gasoline. And it would be a waste of money to favor premium over regular, especially in these times when gasoline prices are high, according to the experts.

Virtually nothing is gained by filling up with a premium or more expensive grade of fuel than the vehicle manufacturer has recommended, the experts say. And many of the same experts explain that drivers may not lose much performance from their cars by using a lower grade of fuel than recommended by the car manufacturer.

There is little difference in energy content of regular versus premium gasoline. They both contain about 111,400 British Thermal Units of energy per gallon.

The price difference, however, between the fuel grades is anywhere from 20 cents to 40 cents, depending on where you live in the United States. The experts' consensus goes against the long-held belief by thousand of drivers who fill up with premium only, or on every third or fourth trip to the pump. The idea is to fill up with premium every so often to clean out the engines or rev up the performance of older engines.

But according to the experts, this practice is like tossing quarters in a wishing well, since most engines are designed to operate on relatively low-octane regular unleaded gasoline.

Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.

The American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command.



For more about this subject, see the excellent article "Fact or Fiction?: Premium Gasoline Delivers Premium Benefits to Your Car Exploding the myth that premium gasoline delivers better performance in the average automobile" by David Biello on Scientific American's website at: http://www.sciam.com/article.cfm?id=...tion-premium-g

 

Uh oh. It looks like the information either didn't come from true experts, or some of what the experts said was incorrectly paraphrased by whoever summarized their conclusions.

It's true that BTU content is roughly the same for the various grades of fuel. But that doesn't mean that the grades can be used interchangeably. What you get with premium gas is greater detonation resistance, and usually a better detergent package. Detonation is a major cause of engine damage.

Many modern computer engine management systems can sense detonation, and adjust parameters to control it and prolong engine life. They do it by reducing power or fuel economy. If an engine is designed around a low octane fuel, these adjustments seldom come into play. But as far as I know, the Harley engine management system doesn't include detonation sensors yet, so the ability to compensate for low quality fuel is very limited.

On top of that, Harleys (except for the V-Rod) are air cooled, so temperatures can't be controlled very accurately. A fuel which is adequate under most situations may not be adequate to protect from engine damage when the motor gets a little hotter than usual.

One big challenge with understanding detonation is that people often don't realize when engine damage has been caused by it. It can cause everything from accelerated wear (fewer miles before needing a rebuild) to banging out the bearings on the bottom end.

(Note: I edited this post from the original version to tame it down.)

 

I love seeing these posts. People are passionate on both sides. I lean towards the use what the MoCo recommends, which I believe is mid-grade. I'd rather spend my money on chrome then premium fuel, which has, IMHO, no benefit other that the bragging rights of "I only use premium in my sled".

 

Absolutely correct! Yes I have learned something and yes I know what's up!!! Not from what I think but from what is real. Detergents have been put into all consumer fuels nowadays. More so with some fuel brands then others. Also all vehicles that use an ECM to control timing and spark are capable of using either fuel rating by reducing spark timing on ignition. This degrades in performance if it is needed. However the theory of octane remains the same. It is what it is for. Period. Just like with a turbocharged engine....Boost is not necessarily a good thing. It is merely a measurement of restriction. Flow is where it's all about.

 

OK then. Gas is gas. Detergent gasoline is detergent gasoline. Don't do a search on "top tier" detergent gasolines.

 

That's because it's running richer. Rich will run cooler but not efficient. Lean will make the most power but run hot and run better chance of hurting the motor.

(Warp Factor) If have no clue where to start with your comment?

 

Here, read this! http://en.wikipedia.org/wiki/Octane_rating

 

A lot of interesting points out there. I learned a lot about fuel thanks for posting.

 

We have premium "pure gas" avail where I live. I use this whenever possible. When I travel I use a smart phone app downloded from PureGas.org that is updated daily and advises where you can get pure gas(non-ethynol) by state/city. A few cycles of the key using non-ethynol premium, you will be impressed by the performance gained. If pure gas is not avail I run premium name brand gas from a high volume station. I prefer Shell, Chevron and Sunoco in that order. Also once a month, I add 4 oz's of Chevron Techron fuel system cleaner to the fuel tank.