High octane gas

I find it very hard to believe that Toyota would recommend using gasoline (87 octane) that harms the catalytic converter.

 

I'm stubborn.
Remember?

~Andrew

 

An earlier post mentioned the Magliozzi bros (Tom and Ray (or Click and Clack)) saying that there's no point running higher octane, but they didn't mention that the brothers also state that running a higher octane fuel than the one intended for your car increases pollution.

See
http://www.cartalk.com/content/columns/Arc...0/April/08.html or
http://www.cartalk.com/content/columns/Arc...996/May/07.html or
http://www.cartalk.com/content/eco/tips.html#4

 

One down and one to go :mrgreen: 8)

 

I'm just not sure about this.

My reasoning for continuing what I am doing is that I tend to have a fuel economy number that is as good or better than the EPA rating.

I change my oil every 2500 miles, use injector cleaner, clean the filter and airbox, inspect the throttle body, maintain good tire pressure, and buy expensive fuel.

I buy from only gas stations that have high customer volume and that maintain a good level of cleanliness at the pumps and the rest of the station. I never purchase fuel from a station if I know a fuel truck just filled the tanks there because I fear getting any traces of silt in my fuel.

Since I don't know which fuel is better for my car (and no one has official proof), I just take a guess and hope that it's the right one.

Here's what I want to do...

I want to see if I can get a mechanic friend of mine to perform a little emissions test with me. I will do an emissions test with 87 octane running through my car, and then I'll do one with 93 octane. I'll post the data for you all to see.

Somehow we'll get to the bottom of this.

~Andrew

 

Since you want to be utterly convinced that you are wasting money we will have to chip away at this one step at a time. Lets start with the API. Keep in mind that the oil industry makes a lot more money on premium than on regular when you read this, and that your Prius is not knocking and that it is not a high performance/high horsepower autobahn burner. We'll go on from there over time.

Long URL CLICK ME!!

 

OK, now lets look at someone else's expanation, in case we are doing a poor job of getting the point across to you

http://www.cheap-auto-car-insurance-quotes...de_gasoline.htm

 

And another one that is just so much more eloquent than I am

"However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.

...

WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?

You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system.  It can also collect in the catalytic converter.  When you over stress any system, it can malfunction or not do what it was designed to do properly.  In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline. "


Read the complete explanation here:
http://theserviceadvisor.com/octane.htm

 

Now we get the FEDS involved, don't mess around with these guys

Facts for Consumers
The Low-Down on High Octane Gasoline

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual.

http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

 

So how about a published mechanic?

http://www.bellaonline.com/articles/art8084.asp

 

Of course, About.com has to get their two cents into the picture!

http://chemistry.about.com/library/weekly/...aabyb100401.htm

 

I think this paragraph from the article is most pertinent (my highlighting). Certainly no one will claim that the Prius engine is either large or powerful:

Cars that have bigger and powerful engines need high-octane levels in the gas. This is due to the fact that the engine is under high pressure and chances of knocking increase. However, if we use premium gasoline in a car which does not have a high performance engine, the fuel might not burn properly, since premium gasoline is harder to burn. This will lead to carbon deposits on the engine leading to engine clogging. This would further reduce the miles per liter and can prove very harmful in the long run. It may also increase emission levels and can cause deposits on the catalytic converter. This would be a big price to pay for a fuel that costs more and believed to be a better one.

 

Bruceha,

I think you've put your finger on one of the most important points. The compression ratio of the Prius is only 8:1, right off the bat, that tells us engineers that this engine is destined for a regular grade of gas.

There is an anomaly in that Toyota has the compression ratio listed as 13:1 in some material. Normally I would look at that and freak out as it is so high that I would not be certain that even premium would have a high enough octane rating to prevent detonation (AKA knocking, AKA pinging).

Fortunately this must be some marketing person at Toyota getting a little over zealous. 13:1 is actually the expansion ratio and all is well with regular gas.

Bob.

 

I'm still wondering if anyone has anything to say about pages 202-204 in the owner's manual. It says things like...

"Toyota recommends the use of cleaner burning gasoline and appropriately blended reformulated gasoline. These types of gasoline provide excellent vehicle performance, reduce emissions, and improve air quality."

"Select unleaded gasoline with an octane rating of 87 (Research Octane Number 91) or higher."
I'm taking this to mean that the emissions and car longevity research done by Toyota was done with 91octane fuel. Please correct me if I am misinterpreting this information.

Please remember that I realize I'm being stubborn and not making the switch to 87, but I would still appreciate any incite or comments about this topic.

Thanks,

~Andrew

 

The Links provided already explain the difference between the US Pump Octane Number and the Reasearch Octane Number (RON).

Quote:

Gasoline pumps typically post octane numbers as an average of two different values. Often you may see the octane rating quoted as (R+M)/2.

One value is the research octane number (RON), which is determined with a test engine running at a low speed of 600 rpm. The other value is the motor octane number (MON), which is determined with a test engine running at a higher speed of 900 rpm. If, for example, a gasoline has an RON of 98 and a MON of 90, then the posted octane number would be the average of the two values or 94.

High octane gasoline does not outperform regular octane gasoline in preventing engine deposits from forming, in removing them, or in cleaning the engine. Consumers should select the lowest octane grade at which the car's engine runs without knocking.

 

Great explanation Danny, but I want to empasize a few points.

Using a higher grade of octane than is necessary:
- lowers fuel economy (because not all the fuel is burned before the exhaust valve opens)
- can damage emissions system components (unburned fuel leaving engine)
- costs more (economic damage)

There are references for these items in my previous post.

Bob

 

Hi Andrew,

Don't worry, we understand that you are being stubborn and don't want to switch to 87. If you didn;t care at all, you wouldn't have posted anything here. We know the correct answer, we are just trying to find a way to illuminate the path in case you choose to take it.

I appreciate that you clarified where your misconception comes from. bruceha_2000, Tempus and Danny and others have help to contribute to a big picture of octane level and Prius ownership.

What we should do is ask you a few questions to make sure that we are all on the same wavelength.

We are all in complete agreement with the Toyota manual. When we say 87 octane, this in our minds translates to regular, not mid-range and not premium. In the manual you are looking at, it is actually saying to use regular octane rated gas.

Does this make sense to you?

Thanks,
Bob