Re: Basic question: 96 Camry V6 Octane

On Mon, 30 Apr 2007 19:43:43 -0700, Zito wrote:


I'm sure the recommendation is 87 or 89. Most cars run well on 87.
I use 93...
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Why? It takes more oil to make a gallon of 93 compared to 87 or 89 (it takes more energy to refine it). And it costs more. And, cars generally don't run any better.
Jeff
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On Tue, 01 May 2007 03:22:12 +0000, Jeff wrote:

My cars run better, get better fuel economy, don't knock, and generally do 10% better with 93.
My Tercel managed 15% better with 93. Over the time I owned the car, I spent ~$240 LESS using 93, based on the difference in milage between *89* and 93. (from 38 MPG to 45 MPG). My Hachiroku does 4 MPG better, my LHS did 2, and my Supra...Who Cares? The car runs good.
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Congratulations. Every report that I have seen that compared cars running 87 octane vs. higher octane for cars requiring 87 octane had similar performance as far as HP and mileage with 87 and 93. You must be doing something special.
http://www.epinions.com/auto-review-43B8-1817227-38951724-prod3
Jeff
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On Tue, 01 May 2007 03:57:09 +0000, Jeff wrote:

I don't believe this at all:
"Mine actually gets about 5 mpg less if I fill it with 93 or 94. Now that is strange."
I'll say. I run 90,91 or 93 in all my cars since 1980, and they all have done better than on 87. When prices get high like they are now I switch every other half-tank, from 89 to 93. This gives me 91. Good for me.
I always notice a difference going to 89, and won't even touch 87.
The cars in question are (were)
1980 Corolla SR-5 (3 MPG difference) 1985 Corolla GTS (4-6 MPG difference) 1987 Corolla Sedan (6 MPG difference) 1985 VW Jetta (don't know the difference) 1988 Honda Accord (5 MPG difference) 1995 Tercel (6 MPG difference from 89 to 93) 1985 Celica (4 MPG difference) Supra (who cares?) Scion tC (what's 87 octane gas?)
A 25 year track record works for me...
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I keep a gas purchase log for all of my vehicles. Over the years I've done the premium/regular comparison many times. I have never been able to detect any significant difference in fuel economy. I've had several vehicles with knock sensor and the claim was that if you used premium, the PCM would adjust the engine parameters such that you would obtain slightly better fuel economy and slightly more power. I have no way to evaluate the power because the increase was relatively minor (3% to 5% - hard to detect without measuring equipment), but fuel economy changes should show up over a long period of time. I've never seen them. I know they should be there, but their is no way they can be more than a few percentage points. I suppose if you have a car getting 25 mpg, a 5% increase would be detectable (26 mpg), but you need careful records to determine this.
Logically, I can't see why you would expect a large increase in fuel economy by switching to premium fuel - assuming the engine runs ok on regular. Most PCMs only vary the ignition timing to adjust for fuel type. While this does affect mileage, the effect at part throttle is small. For conservative drivers, the difference is probably miniscule, since even when running regular, they rarely stress the engine enough to force the PCM to retard the timing. Without changing the compression ration, I think the chances of measuring 6% or greater differences in fuel economy are nil. With premium costing around 7% more than regular, I think buying premium because of a possible increase in fuel economy is bad economics. On the other hand, if you are using your vehicle to haul a heavy load, towing a heavy load, or driving at sustained high speeds, premium might be worth the extra cost IF you have a car that can adjust the engine parameters (and most modern cars can - although to varying degrees). And of course if you have a car where the manual says premium is required, that is what you should use.
From http://www.usatoday.com/money/autos/2003-07-30-premiumgas_x.htm :
"No data show that engines designed strictly for regular run better or longer on premium.
"The Federal Trade Commission, in a consumer notice, emphasizes: "(I)n 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."
"There is "no way of taking advantage of premium in a regular-grade car," says Furey.
"There is no gain. You're wasting money," insists Jim Blenkarn, in charge of powertrains at Nissan in the USA.
"No customer should ever be deluded into thinking there's any value in buying a higher grade of octane than we specify," says Toyota's Paul Williamsen, technical expert and trainer."
From http://www.chevron.com/products/PRODSERV/fuels/bulletin/motorgas/8_q-a/#21 :
"21. Will premium gasoline give better fuel economy than regular? Will one brand of gasoline give better mileage than another?
Gasolines with higher heating values give better fuel economy. Differences can exist, but they will be small compared to the benefits to be derived from the maintenance and driving tips in the above answer.
Traditionally, premium has had a slightly higher heating value than regular, and, thus, provided slightly better fuel economy. The difference - less than 1 percent better - is not large enough to offset premium's higher cost. The difference is likely to be less or nonexistent between grades of reformulated gasoline.
There can be differences in heating value between batches of gasoline from the same refinery 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 the gasoline with a higher heating value.
Also see:
http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm http://www.edmunds.com/advice/fueleconomy/articles/106293/article.html
Ed
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C. E. White wrote:

Ed,
What do you think about this, from a 2004 Highlander manual for the V6 engine:
"3MZ-FE engine: Select Octane Rating 87 (Research Octane 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 (Research Octane 96) or higher is recommended."
I have tried all three grades of gas, and there is not a conclusive difference among them. so what does Toyota mean?
BC
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It seems pretty clear to me - Toyota expects the engine to provide slightly greater maximum power and slightly better fuel economy if you use premium fuel. My belief is, that if you are a conservative driver and you are not doing anything special, you will not likely see a difference. On the other hand, if you are a more aggressive driver, or you are towing, or carrying a heavy load, you might see a difference.
Here is my train of thought - The PCM doesn't know whether you are using regular or premium fuel. It changes the engine parameters based on things it can measure. Your engine has knock sensors. These detect pre-ignition (knocking). They are far more sensitive than your ears. When knocking is detected, the PCM changes the engine operating parameters (chiefly by retarding the ignition) to reduce / eliminate the spark knock. Retarding the timing also reduces maximum power and fuel economy. The amount these are affected is determined by the amount the ignition is retarded. The PCM is continually readjusting the timing to attempt to maximize the fuel economy. People who accelerate gently and aren't otherwise stressing the engine aren't as likely to provoke spark knock even when using regular fuel. Since the ignition is retarded in response to spark knock, conservative drivers may already be running close to the maximum advance that the PCM allows under any condition. So they are unlikely to see any difference if they switch to premium fuel. On the other hand, aggressive drivers, or drivers who stress the engine (towing, hauling heavy loads, etc) might see a big difference (big being 5%) in fuel economy. This is because they are constantly operating the engine in a manner that induces spark knock when running regular fuel. Because of the spark knock, the PCM is usually running the engine at the minimum spark advance allowed (fully retarded). When these aggressive drivers use premium fuel, the spark knock decreases, so the PCM can now go to maximum advance. This allows maximum power and fuel economy.
For your Highlander, if you want maximum power, you need to run premium. This will allow the PCM to adjust the ignition timing to the maximum advance where the engine will produce the most power. The difference is probably in the 5 to 10 horsepower range. But do you often drive at or near full throttle? If not, you are never going to see much difference in power. If you are a conservative driver, I doubt you'll see much difference in fuel economy. However, if you are a more aggressive driver there may be an increase if you use premium (3% to 5% is what is usually quoted). Your Highlander will run just fine on regular. If you are really curious, start keeping a gas mileage log book. Use premium for a couple of months and then switch back to regular. You need to do many tank fulls to get an accurate idea, and of course if you do something extraordinary (like take a long trip) in the middle of the comparison, the results can be meaningless.
Ed
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C. E. White wrote:

That's a clear explanation, Ed. Thanks.
BC
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I did some testiing over a couple of years with my Honda, comparing 87 octane with 91.
If anything, there was either no change in mileage, or a 2% reduction with 91. And that 2% may have been related to the lower temperatures I experienced during part of the test.
Some say higher octane gas contains better additives, specifically more detergents as partial justification for the higher cost. If true, this would contribute to engine cleanliness.
--
Tegger


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That used to be the case in general, prior to 1995 when the feds mandated a minimum level of detergents in ALL fuels.
Now you'll find that Shell (for example) puts more than the minimum detergents in all their grades, and their 93 octane fuel contains 2x detergents than their lower octane fuels.
So if you need to clean out your fuel system, run a few tanks of Shell 93. Once it's clean, run Shell 87 to keep it that way.
http://www.toptiergas.com
Some other major retailers operate similarly.
You can bet that the no-name and grocery store shops meet minimum federal standards--period.
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On Tue, 01 May 2007 08:44:33 -0400, Elmo P. Shagnasty wrote:

When I was working in VT I was using Shell. They don't add Ethanol like in Mass. When I fill up in Mass I use Gulf. Because it's convenient.
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Top explanation ed.
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wrote in

Everybody usues ethanol now. They've all been strongarmed into it by the Feds. The modern alternatives are MMT and MTBE, both essentially prohibited.
Go check out the MSDS sheets for the various companies' gasolines.
--
Tegger


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Actually, I think ethanol use varies greatly by geography. At least for now in NC, we don't have to use the stuff. A few years back our winter gasoline had either MBTE or ethanol, but they finally stopped making us do that. I know some states (Minnesota for sure) require 5% ethanol in all gasoline.
Mobil has a decent FAQ at http://www.mobil.com/USA-English/GFM/Products_Services/Fuels/Gasoline_FAQ.asp (or http://tinyurl.com/h6xan )
There is a fuel requirements map at http://www.mobil.com/USA-English/Files/US%20Gasoline%20Map%20100102.pdf (or http://tinyurl.com/2bdmk8 )
The map shows that much of the northeast coastal areas require ethanol in the gas.
Chevron also has good information on gasoline at http://www.chevron.com/products/prodserv/fuels/bulletin/motorgas/ (or http://tinyurl.com/yucftl )
Ed
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On Wed, 02 May 2007 08:54:18 -0400, C. E. White wrote:

Mass requires Ethanol, VT does not:
http://www.mobil.com/USA-English/Files/US%20Gasoline%20Map%20100102.pdf
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wrote in

Eh, I f***ed up. What can I say?
My province just mandated the use of ethanol. Minimum 5% now, rising to 10% in three years.
Envirowackos. Eco-fascists.
--
Tegger


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On Wed, 02 May 2007 16:56:45 +0000, Tegger wrote:

That's OK. I made a mistake, too. Once. ;) (I think it was buying a VW. Either that or getting married..EITHER time...)

Interesting. I started filling my Mom's car up where I get my gas, and she asked me what I put in it (knowing I pay the extra $$$ for 93 Oct...)
I told her the 87 Oct at the station downtown. She said the car ran a lot better and "takes longer for the gauge to go down." They run 10% Ethanol there...
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BWAHAHAHA, that was good one

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Don't forget the farm lobby. Last year I sold corn for around $2 per bushel. This year I have already contracted to sell it at over $3.50 and I am worried I signed up too soon. Last year my profit on corn was negligible. This year I might actually make money.
Ed
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