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Hi Octane fuel in regular engines

Hi Octane fuel in regular engines

Hi Octane fuel in regular engines

(OP)
Why do they recommend hi octasne fuel in regular engines?
They say it will clean out the cylinders/carb. Others say for an engine designed for regular fuel(unleaded) it is just a waste of money. Does the higher compression engines actually burn this higher octane. How high has the compression ratio to be?

 

RE: Hi Octane fuel in regular engines

Hi octane fuel, in and of itself, will not clean out the cylinders (AFAIK).  It will, however, allow for a highr compression without knocking. If your engine is designed for low octane fuels, then yes, your money is mostly wasted by going with something of a higher octane.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Hi Octane fuel in regular engines

High octane fuel from some gasoline distributors contains higher levels of additives/cleaning agents. This is because higher compressions engines are more susceptable to knocking even with a higher octane fuel if there is any carbon buildup.

Putting a tankfull of higher octane fuel in a car may help clean deposits even if the car does not require the higher octane. But it's better and cheaper to just add a bottle of additive to your tank.

RE: Hi Octane fuel in regular engines

Bam55

There is so much hogwash about on this subject it is ridiculous.

Octane rating is the ability to prevent knock. High compression causes knock by igniting the fuel prematurely or spontaneously across the chamber instead of as a progressive flame front.

You only need just enough octane to avoid detonation or knock under the most adverse operating conditions you will encounter. Any more is wasted.

Any correlation between engine cleaning and octane rating is purely coincidental or due to other additives that may be added to support the premium claim and price. In fact, the most common octane boosters currently used in premium pump fuel are aromatic hydrocarbons and these tend to leave more carbon deposit than apathetic hydrocarbons. Alcohol is also sometimes used as an octane booster. It burns cleaner than the apathetic hydrocarbons.

The cheapest way to remove deposits is to do a power run with a fine stream of water aimed into the throttle bores. A windshield washer hose works fine. Just be careful not to run the water while the engine is not running or you risk damage from hydraulic lock.

Modern engines in good condition that are often run long enough to spend reasonable time at normal operating temperature and occasionally at highway speed, and tune run on good fuel of sufficient, but not unnecessary octane rarely if ever need cleaning.

The following links are a wealth of information on this subject.

http://blizzard.rwic.und.edu/~nordlie/cars/gasoline.html

http://naca.larc.nasa.gov/

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Hi Octane fuel in regular engines

Quote:

There is so much hogwash about on this subject it is ridiculous.

Thanks, Pat.  You saved me a bunch of typing.  I will never understand these urban legends...how the heck do they just keeeeeeep on going and going and......

Rod

RE: Hi Octane fuel in regular engines

The brilliant marketing on the part of the oil companies since I was knee high to a grasshopper of calling low octane fuel "regular" gas and high octane fuel "premium" gas.  You still see this today, often times referred to as "super" unleaded.

RE: Hi Octane fuel in regular engines

(OP)
OK Thanks,

Thats the kind of information I needed for reassurance.

Motto from this: Why make things complicated?

RE: Hi Octane fuel in regular engines

If you need proof about whether premium fuel helps clean an engine or if it helps an engine designed for low octane fuel perform better, the FTC has gone after oil companies for making these unsubstantiated claims and the oil companies could not prove their claims.

About ten years ago the FTC went after Exxon because they made unsubstantiated claims that their 'premium' high octane fuel would make the engine cleaner and reduce maintenance costs.  Exxon could not prove their claims, so they had to produce ads telling customers that most cars did not require premium fuel, and unless your car specifically required it, using premium fuel would not help.  http://www.ftc.gov/opa/1996/09/exxon1.htm

Amoco agreed not to say that their premium fuel would improve engine performance or clean your engine after the FTC went after them.  They agreed to this because they could not provide scientific proof about their claims.
http://www.ftc.gov/opa/1996/02/amoco.htm

Bob

RE: Hi Octane fuel in regular engines

I agree with everything that has been said before, but my 1999 Honda Accord definately has more wide open throttle power when using premium gas (based on "The Butt" dynomometer).  I attribute this to the ping sensor not backing off the ignition advance when using premium fuel.

RE: Hi Octane fuel in regular engines

UK testing

http://www.thorneymotorsport.co.uk/gcs_article.php?artid=64&;typelink=http%3A%2F%2Fwww.thorneymotorsport.co.uk%2Fgcs_article.php%3Ftype%3DNews%26subtitle%3D0%26title%3D0%26text%3D0%26toc%3D1
may not apply to regular engines and may only benefit certain engines

My understanding with UK fuels that a few years ago the so called cheaper Supermarket fuels although same Octane used less additives compared to a branded fuel.

RE: Hi Octane fuel in regular engines

I'll bet there are some of you, that should you try hard enough, could "prove" to your "butt dyno" that the "fuel magnet" will make your car run, better, faster, get better fuel mileage, etc. ad naseum! You can even buy a little stainless steel "Q-Ray"  bracelet for only two payments of $49.95 that will make life "so much easier"...Sorry, the "butt dyno" won't work on this one.--- Guys, ya just gotta stick with the folks that do this stuff for a livin'. Maybe you should keep an eye out for that long lost relative that left unclaimed "millions" in an account in Nigeria.

The trouble with 'butt dynos' as I see it is 'constipation'!

Rod

RE: Hi Octane fuel in regular engines

Or more accurately the evidence of a lack of constipation in the bull pen.

Premium fuel will give more power and mileage for high compression engines with knock sensors as with lower octane fuel, the knock sensor will retard the spark to stop knock.

This has all been covered before. The inbuilt google search engine will find it for you so we do not need to go over it all again, and again and again etc etc.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Hi Octane fuel in regular engines

One thing that hasn't been mentioned in this thread - high octane fuel is created with additives that displace gasoline with the end result less BTU/gal. Again backing up Pat - "You only need just enough octane to avoid detonation or knock under the most adverse operating conditions you will encounter. Any more is wasted."

ISZ

RE: Hi Octane fuel in regular engines

I thought Toluene had more energy but ethanol less.

RE: Hi Octane fuel in regular engines

I think you are correct. Ethanol definitely has less. I would expect toluene has more due to the double bonds, but my chemistry has gathered 40 years worth of dust.

I provided the link so the OP could do his own research.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Hi Octane fuel in regular engines

No, toluene has a slightly lower calorific value than gasoline, by weight, but is much denser, so by volume it has a higher energy content. The main contributor to CV is the hydrogen, all the carbon really does is provide a good way of storing hydrogen. That's why the shorter hydrocarbons have higher CVs. Toluene 'wastes' links by double bonding to carbon, rather than storing more hydrogen.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Hi Octane fuel in regular engines

I understand that fuels sold in UK except Shell Optimax (V power) Tesco 99 (Ethanol) and perhaps BP Ultimate (noticed run on using this), are basically and often literally, exactly the same base product in to which each company puts in their own additive package. i.e you will see all kinds of tankers filling up at a Shell distribution site, Texaco, Esso, BP, Sainsburys, Tesco etc. etc. and they all fill up with exactly the same base fuel, i.e. they all share distribution points in order to reduced transport costs, but each company will add its own additive package at the filling gantry. Whether some additive packages are as good as others may be debatable!

I understand that Optimax is produced from a completely different base product than all other gasoline products available. The base fuel used is more highly refined than normal gasoline, hence the superior performance. Also the additive package used amongst other things is extremely effective in cleaning the engine inlet tract and combustion chambers. When used in engines that have previously only used "normal" gasoline, Optimax cleans these components to an as new condition!

Optimax was also subject to "overadvertising" but the claim was not upheld effective detergent additive,
http://www.asa.org.uk/asa/adjudications/non_broadcast/Adjudication+Details.htm?adjudication_id=37402

An additional advantage is that, due to their different composition, "premium" fuels are typically two or three percent more dense than "normal" fuel, which means that each litre contains two or three percent more mass of fuel, and hence two or three percent more energy. All other things being equal, that automatically translates into a two or three percent improvement in fuel consumption (miles/gallon or litres/100 km).

http://fuelsaving.info/fuels.htm
I also understand Optimax to use Toluene in their fuel

Toluene is denser than ordinary gasoline (0.87 g/mL vs. 0.72-0.74) and contains more energy per unit volume.

http://www.elektro.com/~audi/audi/toluene.html

The other additive that is being advertised with Texaco fuel in Ireland is Techron
http://www.chevron.com/products/prodserv/fuels/techrongas/

Then with the Dyno testing the Tesco 99 Ethanol fuel produced the goods.

Perhaps a grain of truth but not value for money?

RE: Hi Octane fuel in regular engines

Quote:

An additional advantage is that, due to their different composition, "premium" fuels are typically two or three percent more dense than "normal" fuel, which means that each litre contains two or three percent more mass of fuel, and hence two or three percent more energy. All other things being equal, that automatically translates into a two or three percent improvement in fuel consumption (miles/gallon or litres/100 km).

Hmmmmmmmmm?

Rod

RE: Hi Octane fuel in regular engines

It is more likely to translate to 2 to 3% rich mixture unless the fuel metering system corrects at that level.

Carbies certainly won't EFI mostly will in increments of a size I don't know, but I am sure someone else here will know.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Hi Octane fuel in regular engines

Well, since I'm sorta 'anal' about this...and mostly to the OP's original question...

2001 Lincoln LS V6 purchased new March 20, 2001.

Premium or 91 octane recommended by OEM and used from March 2001 until May, 2002---
Regular or 87 octane used from May, 2002 until present---

106 miles daily during the week for 90% of the cars life (wife's car, to work and back, now at something near 145,000 miles and counting, still on OEM sparkplugs and just passed it's first mandated California smog check)---
Fuel mileage has NEVER varied outside the min/max of 21/22 mpg...EVER!  I've kept track of lots of my cars in the last 49 years and have never documented notable variations in fuel mileage using "premium" v "regular", carbureated or fuel injected, supercharged/turbocharged, automatic/manual trans, unless the engine in question was modified to the point where "regular" could not be used under any conditions.  This is "strictly street" stuff and, obviously does not include my race engines or cars which typically use ~110 octane race fuel.

There are obviously some caveats in this statement...In the '60's "premium" could be as high as 100+octane and regular could be as low as 62 octane (depending on where you were in North America)...Some of the Detroit offerings had high compression engines that just barely operated on "premium", granted...That is not the point, that was 'then' this is 'now'.  I'm just gonna need a lot more "documentation" before I just sign off on another "urban legend". 2%---3%---sorry, I need more
than casual 'guesstamation'!

Rod

RE: Hi Octane fuel in regular engines

Rod

I'm not convinced by that statement. An original test when Optimax 98 arrived in UK (now Vpower 99)showed no improvement for a Clio

http://fifthgear.five.tv/jsp/5gmain.jsp?lnk=601&featureid=143&pageid=273

Conventionally, enrichment for maximum power air/fuel ratio is used during full throttle operation to reduce knocking while providing better driveability; perhaps the more dense Optimax   may gived the "claimed" better response.

RE: Hi Octane fuel in regular engines

I'm sorry, Knap.  Which statement?  I think the consensus here, as I see it, is that using premium or at least a 'better' grade of fuel than the engine requires is a waste of money.  As Pat puts it, run the cheapest grade of fuel that gets the job done.  I see no gaines, either power or economy, in using the high priced premium or mid grade fuels (which are just a blending at the pump, anyway) when the car will operate with 'regular'.  I have pointed out that in some cases,eg, early muscle cars, need premium, that's fine...they do not, however, need 110+ race fuel (I see this $5+/gal stuff used by local kids on the street...I just scratch my head.)

Rod

RE: Hi Octane fuel in regular engines

Rod

This statement

    An additional advantage is that, due to their different composition, "premium" fuels are typically two or three percent more dense than "normal" fuel, which means that each litre contains two or three percent more mass of fuel, and hence two or three percent more energy. All other things being equal, that automatically translates into a two or three percent improvement in fuel consumption (miles/gallon or litres/100 km).

RE: Hi Octane fuel in regular engines

/If/ you are on closed loop

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Hi Octane fuel in regular engines

From GPSA data table: BTU/gal (UHV)

tolulene 132658  
iso Octane (100 Octane) 119396
normal octane (0 Octane) 121428
benzene 132671
ethanol 84511
methanol 64744
straightrun gasoline (about 75 octane) 120000
iso butane 96 octane 90905

RE: Hi Octane fuel in regular engines

Rod,

It depends on what "those street" kids are running under their hoods.  If they're running high compression pistons, or more likely heavy boost, the high octane keeps them from blowing up.  These days it's easy enough to turn an electronic dial on the blow-off valve to go from using high-octane pump gas (93) to super-octane (110+), so they can keep a high-boost blower under the hood but still have streetability when the good stuff isn't available at the pump.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Hi Octane fuel in regular engines

Kind of a dumb article...

First they test with fuel 'A' with a standard RON for the baseline.  Then they change to fuel 'B' with a higher RON, but modify the maps at the same time (great comparison!).  Then they increase the boost for the third test.

Just what are they comparing, the engine's ability to use more power with a proper tune?  If they wanted to impress me, they'd show me some power gains with a change in fuel and no change in maps or boost.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Hi Octane fuel in regular engines

Knap.
I am not at all convinced by that statement either.  I think it is totally bogus, or at least biased by 'fudging' the tests results. You know the cliche about 'statistics'?
As to the BP article---Am I to believe that if I put 102 in my 1930 Ford (<5:1 CR) it will boost my horsepower by 60 hp?

Dan.
I agree.  However, trust that I have sufficient experience in this area to be able to tell the difference between the 'real deals' and the 'street squids'.  I live just three blocks from the local high school and I see some pretty  strange mods on the street.  I have talked with some of these kids on occasion, especially when I'm filling the jerry cans with a race car in tow.  They 'appear' to comprehend my reasoning when I tell them they are wasting their money on the 'race' fuel (Who can really tell, though). It is also quite common to see the dirt bike guys using VP and Sunoco ~110 in stock dirt bikes. The 'word' is that it gives them extra hp.  Re: above statement about the BP article!

Rod

RE: Hi Octane fuel in regular engines

Gee, I used to do the same thing in the dark ages by recurving the distributer, bumping base timing 2-4 degrees and using premium.  Actually did see reduced ETs and better mpg.  So I guess the higher octane works.  Oh, did I mention recurving the distributer and bumping the base timing?

RE: Hi Octane fuel in regular engines

Picky, picky, picky.  There's always one. I'd give ya a "pale pink" star if I my feelings were not hurt!!! Your obfusgating the issue. ;o)

How's the kids...still doing the 'ambulance' thing?

Rod

RE: Hi Octane fuel in regular engines

Rod - first daughter married a Navy man, he went to the Seaman to Admiral program and I administered his commisioning oath.  I now have two granddaughters and the daughter is going for her LPN (15 months).  Daughter #2 is now doing the EMT thing, including passing the emergency vehicle ops course - good for a 15% insurance discount.

RE: Hi Octane fuel in regular engines

Here's my question.

I drive a Mercury GM with a 4.6L V-8 engine, factory stock, second set of plugs and have put about a half million miles on 3-4 of those things in the last 15 years.  I like'em.  I don't think the engine has a knock sensor, or at least if it does, it doesn't work too well, because in the summer month especially that engine will ping just as long as you want to keep your foot on the foot feed at that position.  I don't like to drive it pinging down the road.  I do often put the next grade up in or at least do it on an every other tank basis, as I am basically in agreement with the consensus that higher octane fuels are a waste in engines not designed for them.  But I do notice a ever so slight improvement in the mileage when I do it.  It may be that now that the engine is not pinging itself down the road it is delivering more horsepower to the wheels, which is what I want it to do anyway.

I also have some engineering experience in fuel pipeline stations where the tanker trucks load, and I have many times seen the tankers from all brands all filling from the same tank filled from the same pipeline and have talked to the drivers as they did the additive thing.  That to me is suspect, as drivers are as human as the rest of us and if his wife beat him that day before he left for his haul, he might just forget to add the package, or might do it twice.  What about rainy days when it is coming down in buckets-does he bother?  Who knows and where is the quality control guy checking him-I never saw one.  How good does it mix?  Did he add it before he filled so that he got good mixing, or put it in when the tanker was full as an after thought?

In my former life, I drove lots; sometimes requiring several fill ups a day.  As a practicing ME, I think I have the ability to understand the variability of fill up levels and take into account the variations.  Mostly, however, since I am basically lazy and don't count time standing at a gas pump as productive (not to mention the frustration of having to try to figure out how to operate modern pumps-the guy who designed kitchen microwave controls and television clickers designed the gas pump controls) I fill it to the brim.  Multiple click off's until it is full and won't take any more (even with the occasional rocking the car).  I also note whether the car is on a mostly level surface, or if it is tilted in any manner.  I know just about how much it will take to get to the first click off and just about how much I can 'stuff' into it by working at it.  Those of you who drive your cars lots of consistent miles know what I mean.

If I had a dollar for every time I had filled a vehicle, I'd be long retired.

That all said, every now and again, the mileage will suddenly jump noticeably.  While on a good day when I am driving decently, mostly turnpike driving, not much in town driving, no excessive speeding (rare, but I can do it) I get a steady 22-23 MPG (I have the power package with a different ratio rear end so I get less than the std. GM.)  

But from time to time, not often, but often enough to raise up a question in my mind, the mileage will jump to the 24-25 MPG range, and I didn't do anything in particular to obtain that.  Remember determining this is always after the fact on the next fill up.

Anybody got any idea what might bring this on????

I have a theory.  My theory is that if a jobber has an excess amount of higher octane fuel in stock that he has to move, that he might drop it into the 'regular' tank and sell it at 'regular' prices just to turn his inventory.  I can't prove it, but I have never come up with any better explanation of why the random increase in fuel mileage.  It certainly wasn't anything I did.

Usually this happens to me in a situation where I can't go back to the station where I go the 'hot' load and try to repeat the results.

I'd be curious to hear the experts on this.

Pat-I got into this thread late, but gave you a star for your first post in it.

rmw

RE: Hi Octane fuel in regular engines

rmw...
I couldn't have said it any differently.  One thing I do is take several tanks in a row and average instead of doing it every time.  Actually, that's how I kept from going to sleep on the road, I did math problems in my head (along with the day dreaming and general daily 'worry') to project costs, etc.  I'm sure your familiar with that.

One of the caveots in all this is "use the lowest grade that your engine requires"...If that baby is pinging (pinking) then, either retard the timing or go up one step in the fuel grade.  I know you like the big Mercs (from earlier posts) so I am a bit surprised you don't have the pinking problem solved.  Sure, it may cut power a bit, but fuel mileage does not usually change.  Hey, it's a land barge, anyway. winky smile

I worked at many of the L.A. area refineries and have seen Texaco trucks loading at the Union 76 dock and observed the "Out to Mobil" lines at the Texaco tank farm, etc.  I also asked about this and the driver just shrugged and said all he did was 'load it up and deliver it'...no additive, no 'nothing'!!!

Rod

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