Re: More on Top Tier gasoline

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Actually hydrogen is not a good example to use. It has a high RON rating (research method) and a low MON rating (motor method). In an Otto Cycle engine hydrogen tends to pre-ignite and therefore acts like a low octane gasoline.

And as I said before - how you drive will have an effect as well. Someone who almost never drives at WOT is likely to see less of a difference than someone who routinely drives hard.

I was taught that higher octane gasoline had a lower energy content than regular when I was in college - 30+ years ago. However since then I have seen many credible sources saying this is not true.

From

: "Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving. There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify gasoline with a higher-than-average heating value."

Other interesting references:

or It is my opinion that if your car was designed to run on regular, running premium is a waste of money. Although the engine may be able to adjust some parameters to increase performance and fuel economy, the changes will be minor. On the other hand, if your car was designed to run on premium (because of turbocharging/supercharging, a higher compression ratio, or other inherent design factors) then running regular may drastically effect your performance and fuel economy even if the PCM can adjust parameters to protect the engine from excessive pre-ignition.

Regards,

Ed White

Two tanks of the non-brand gas and you already have problems ? I think it's all in your head. hy-vee is not a gasoline manufacturer. They buy their gas from one of the big names. There is nothing wrong with the gas, the only difference could be in detergents. Results will only show up after many many miles, if ever. Buying higher grade gas than what the manufacturer of your car specified is a waste of money. If you really want to feel better , add a bottle of techron or seafoam to your tank every 6 months and buy the cheap stuff. The only gas I don't buy is from small gas stations that don't sell a lot of gas. They might have old gas and cut corners when changing filters in their pumps.

Define "grade".

Gasolines with good additive packages that include good detergents to keep the fuel and combustion systems free of crap--now, those are good grades of gasoline.

Funny thing--the manufacturer of your car doesn't specify what GRADE of gasoline you should use.

I think you mean "octane" instead of "grade". Octane is not a measure of "goodness". It's a measure of the fuel's ability to resist knock and preignition. It's a property of the fuel--like color, it doesn't make the fuel inherently "better" or "worse". It's just a property.

You've bought into the fuel company "premium" hype.

yeah yeah, I meant Octane.

Grade is a term used by the petroleum refining industry to classify types of gasoline. Basically gasoline is pumped into pipelines for distribution, The grading system is a way to determine the value of the product so that exchanges and sales can be made. Octane is the main criteria for determining each grade.

Most people agree that if you go below the octane requirements for a given engine that your mileage will go down and if you purchase gasoline that goes above the octane requirements you won't get any benefit. That seems like a pretty simple proposition but in reality it is a whole lot more complicated. It's complicated by the fact that you really can't be sure what the exact octane requirements are with out careful real world testing. =

I suppose you think there isn't any difference in quality of beef cuts or that there is no such thing as "better" or "worse" when it comes to types of wine? =

Whether high octane is "better" or "worse" depends on what you are interested in. Octane certainly is the single most important property with respect to fuel economy. The reason the price is higher and people pay more for premium is because A) It costs more to produce B) In some vehicles it is cheaper to run using premium. C) regular may cause damage to some vehicles. (note: I'm not saying B) applies to every person who purchases premium and C) doesn't apply to very many modern engines)

Here is a list what J.H.Gary's "Petroleum Refining Handbook" says about the impact of octane on gasoline engines. The assumption here is if everything else would be kept constant this is how these factors affect a typical engine's octane requirements:

Combustion chamber deposits 0-12 RON =

Altitude (air pressure) 3 RON for every 1000 ft. Spark timing 3 RON for every 2 degrees Engine speed 1 RON per 300 RPM Engine Temperature 1 RON per 10=B0F =

Intake air temp 1 RON per 20=B0F Humidity 1 RON per 20%RH

He doesn't say anything about spark plug voltage and gap, EGR concentration, and Air/Fuel ratio, or engine load which also are all known factors that alter the engines octane requirements. =

Engine management and it's sensors are designed to deal with a good many of these factors so for instance timing is used to offset many of the other factors. But sensors that measure these factors aren't perfectly accurate or reliable. Just add up the possible normal deviations and it is easy to see even in engines that are working 100% as designed it is possible to deviate from the norm by more that 2 octane points. And what about the millions of cars that aren't operating 100% as designed?

In isolation anyone of these factors is pretty simple to understand, but when you combine everything together it becomes very complex interactive system. Anyone (including the car's manufacturer) who tells you they can predict with certainty what the effect of purchasing higher octane fuel will have on any particular car's fuel economy at any particular time or place is talking thru their hat. There are just too many different factors beyond the scope of their knowledge for such a statement to be anything but a guess. =

-jim

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You would be mistaken, just as you're mistaken when you compare cuts of beef to gasoline.

yeah. Gee, you're right. Honda's engineers are pretty much stupid, and don't know anything.

Sure. Uh-huh.

No. If you had ask I would respond that Honda's engineers are among the best. But as far as I know all that they say about mileage estimates on their vehicles is something to this affect: "Your actual mileage may vary". It would be pretty pointless for the engineers to enter into a technical dialog with customers about the numerous factors that contribute to the wide range of mileage that their customers get from the same make and model vehicle. I mean look at your response - it appears the only thing technical that you were able to grasp and respond to was the analogy I made between grades of beef and grades of gasoline.

-jim

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Ed, that Car Talk page is a great link. Thanks for providing it. I'm copying part of it into the newsgroup for permanent archiving.

CarTalk.com passage:

It's true that premium gas does contain special or extra detergents, but in our opinion they're of no additional benefit.

Our advice is to ignore any sales pitch about the super-special detergents that come in the premium-grade fuel.

These days, all of the gasoline from the major gas companies contain more than enough detergents to keep your engine clean. Period.

The only reason you might have a use for the extra detergents in premium, is if you have a noticeably dirty engine, and need to scrub carbon and other crud off engine components. (And, if you're doing that, we'd instead suggest that you toss in one of the many fine engine additives.)

You said "major gas companies." Is there a difference in the gas between the big names, and the El-Cheapo gasoline at my local Costco or Stupey-Mart?

There is. A number of years ago, some of the major auto manufacturers were ticked off with the deposits from gas that met EPA detergent standards. In other words, they were afraid they'd take the heat for problems, when their customer's engines clogged up from the twigs and dirt that was getting deposited on their fine handiwork.

So, they set their own guidelines, which they call "Tier 2." All of the gas from the major gas companies meets the Tier 2 standards. The gas at your local Quickie Mart probably does not. The difference? In some tests, after about 10,000 miles, there was a minor amount of crud built up on engine components that ran exclusively on Quickie-Mart gas. Do we think this is an issue? Not really. But, would we advise running your car for 100,000 miles only on Quickie-Mart gas? Not if you're concerned about the longevity of your vehicle. We recommend switching back and forth between Tier 1 and Tier 2 =97 maybe every other tank full =97 to keep your engine running clean.