GeneralDisorder Posted January 3, 2004 Share Posted January 3, 2004 Why is it that everyone must run the highest octane even tho they don't need it? Can someone please explain why otherwise intelligent people *refuse* to belive that you should run the lowest octane you can without pinging? The lower the octane, the more combustible the fuel is, and therefore you will get a more complete burn, and better mileage..... just because you have been brainwashed by the fuel companies into thinking higher is better does not make it so..... run what the manufacturer recommends for your engine..... GD Link to comment Share on other sites More sharing options...
beauregaardhooligan Posted January 3, 2004 Share Posted January 3, 2004 GD, the FSM recommends no less than 90 octane for my '84 EA81. You can adjust any motor to run on any octane without pinging. I have experimented with different octanes in FERTHER and it definitley runs better on the hi-test. The mileage is slightly better on the hi-test, which may not off-set the increased cost, but the performance increase makes it worth it to me. The difference is especially noticeable when passing at speed on the hi-way. Link to comment Share on other sites More sharing options...
Stupidru Posted January 3, 2004 Author Share Posted January 3, 2004 Dave, thanks for chiming in...us ea81t owners have to stick together. Fuel economy/octane discussions always bringout the best on usmb. Don't get discouraged, some members are GenerallyMiserable. Did you take any snapshots of your TBRAT yet...I would really like to see it. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 3, 2004 Share Posted January 3, 2004 No less than 90? Good Lord! But that is completely wrong.... The descripincy of the FSM could be due to it's age. There are two ratings of octane for gasoline - research octane number (RON), and motor octane number (MON). These are placed into a simple forumla to come up with what you read at the pump. Right now, that formula is a simple average: (R+M)/2. However - it was not always this way. Back in the eary 80's when your car was produced, the availibility of leaded gasoline meant a different formula for calculating the resulting "pump" octane of the fuel..... Here's a link for ya'll: http://www.csgnetwork.com/octaneratecalc.html It explains some key points such as: 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. Occasional light knocking or pinging won't harm the engine, and doesn't indicate a need for higher octane. On the other hand, a heavy or persistent knock may result in engine damage. Here's another good page: http://www.leeric.lsu.edu/bgbb/7/ecep/trans/b/b.htm said there: Many vehicle owners believe that higher octane fuels are better for their vehicles since they are labeled "PREMIUM." The logic is that since it is a premium fuel it must be better. In reality, the premium label originates from the higher cost to refine and the resultant higher retail cost. Some refiners label their high octane fuels "SUPER." Some owners think that these fuels will make their vehicles more powerful. Only engines with high compression ratios can deliver all the potential energy from higher octane fuels! Always consult the manufacturer's octane recommendation to determine the proper octane requirements for any given vehicle. Generally, engines with compression ratios of 9.3 : 1 or less will safely operate with unleaded 87 octane fuel. Engines with higher compression ratios usually require higher octane fuels. I can give you more links if you like...... and your EA81 is nowhere near 9.3:1 BTW, and 87 octane should be more than adequate. If you do as they sugest, and: For each grade of fuel, use the MPG and cost per gallon to project the fuel cost to operate this vehicle for 10,000 miles. I think you will come up some interesting results.... GD P.S. - Stupidru - lose the attitude - it's not neccesary here, and it looks bad for someone with a low post number such as yourself. Link to comment Share on other sites More sharing options...
riverrat Posted January 3, 2004 Share Posted January 3, 2004 I run 87 around town but on my week end trips to the coast I run a higher octane simply because the riverrat handles the hills,at freeway speed better than with the lower octane.It just runs better out there for some reason.I am guessing less preignition lugging up the hills in 4th I do agree that alot of people are mis guided at the pumps though.My 2002 mercuary cougar came with instructions not to run any higher than 87 so does the 99 exploder I believe. Link to comment Share on other sites More sharing options...
beauregaardhooligan Posted January 3, 2004 Share Posted January 3, 2004 Quote whoever you like, I can demonstrate what I say. Come to G,vl and I'll show you. The proof is in the puddin'. ...and where did you get leaded fuel in the '80s? My Subaru was designed for unleaded. Newer cars with injection and computers can run any octane because their electronics monitor the combustion about 60 times per second and adjust accordingly. I'm not saying it won't run well on regular, I'm saying it performs better on Hi-test, and I can prove it. Link to comment Share on other sites More sharing options...
Stupidru Posted January 3, 2004 Author Share Posted January 3, 2004 You go Ed! Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 I want scientific proof - not demostrations - write a paper and submit it to a journal - how many degrees do you have in physics and chemistry? mechanical engineering perhaps? These are the people I will believe. Maybe you and all the guys who get 100+ MPG from their special carburetors can get together and come up with some degrees in these fields..... 99.9% of all the information in the world is availible ONLY in written form - learn to love it AND use it..... Leaded fuel was availible here in the early 80's. Maybe not where you live - that I don't know.... Here's a quote from the EPA's web site to this effect: Lead has been blended with gasoline, primarily to boost octane levels, since the early 1920s. EPA began working to reduce lead emissions soon after its inception, issuing the first reduction standards in 1973, which called for a gradual phasedown of lead to one tenth of a gram per gallon by 1986. GD Link to comment Share on other sites More sharing options...
dave valiant Posted January 4, 2004 Share Posted January 4, 2004 I am not some mind numbed robot here. I run the 91 because I get the best fuel economy from it. I have run 85,87and 91. I figured that if Im getting the best fuel economy with 91 that it is running as eficiently as possible which I would think would be a good thing.I may be wrong but thats the logic Im runnin with. As far as photos of the Brat I dont have a digital camera or a scanner Im thinking of taking some pictures and having them put on a disk at the photolab and trying to post them.Perhaps someone on the board could give advice.But not now Ill ask on a sperate thread. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 Have you compared the difference in mileage with the difference in price per gallon? You may find a discrepency in your logic there.... One thing that CAN cause you to need higher octane - carbon buildup in the cylinders can increase your comression, and require you to run higher octane to counteract the resulting ping... the increased mileage in this case has nothing to do with engine design, and everything to do with an old engine, and bad maintenance.... GD Link to comment Share on other sites More sharing options...
dave valiant Posted January 4, 2004 Share Posted January 4, 2004 Well I guess I could save a few more pennys per fillup than I already do. I buy all of my gas from Sams club here in Rapid and the last time I filled up the 91 was 8 cents per gallon cheaper than the 87 at any station here. You mentioned buildup causing the compression to increase could be the reason I get better MPG with 91 and the cause of the buildup could be poor maintenece. Were you talking about general maintenence like oil changes or a typical tuneup like cap rotor plugs wires fuel and air filters Ive always kept up on those am I missing something that should be done at regular intervals. I am not trying to be a smart rump roast here I do not doubt that you know a whole bunch more about Subarus than I do but if one of us newbies such as myself were missing something you find obvious why not just give us a little help. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 No - I'm sure you have all the maintenance down just fine. Carbon buildup is a fact of life - it's going to happen no matter what. You can help the situation by changing the oil regularly - thereby prolonging the life of the rings, and valve seals who's job it is to keep oil out of the cylinders. Also - running a *lower* octane fuel will burn hotter, and leave less buildup than running a higher octane fuel - the lower the octane, the hotter, and more completely it will burn. Running a high octane fuel in an engine not designed for it, will only result in faster buildup of carbon, and shorter engine life due to all the crap that isn't being burnt and getting into the valves and eating up the seals. Not to mention the unburnt blow-by that gets by the rings and into the oil, and thins it out, and fills up the filter with disolved carbon - making regular oil changes that much more neccesary. Carbon scores the cylinder walls, and eats the rings up...... basically it's just bad stuff in general. And I'm not saying I know more about Subaru's than anyone here... just relating what I've learned in school, and what I know about internal combustion engine theory of operation. Trying to educate the readers of the board - nothing more. Please - ask away with your questions - I'll be glad to answer anything I can... GD Link to comment Share on other sites More sharing options...
dave valiant Posted January 4, 2004 Share Posted January 4, 2004 Thanks GD that makes a lot of sense. Do you know of any additives that you could use to help get rid of the buildup in the cylinders or at least lessen it a bit. As far as the last part of your reply I said you know more about Subarus than I do not anyone.Ive read your replys to peoples questions most of which I have no answers for. It was a compliment.USMB for life Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 Actually - one way to do it is to run straight water into the intake..... no seriously! If you take the hose, and run a constant stream of water down the carb or throttle body, it will basically steam clean the inside of the cylinders. I doubt seriously that any kind of additive would work as well as the steam cleaning approach. The techron stuff Chevron puts in their gas is supposed to help.... although I have not done any research on what that stuff is, or what it does. Might be worth looking into. When doing the water thing - rev the engine up to a couple grand, and run the water through till it slows down to about a grand. Don't kill it! You want to do this with a warm engine that has been fully heated up Afterwards - change the oil and filter so no water can remain in the oil to cause problems later... GD Link to comment Share on other sites More sharing options...
Nug Posted January 4, 2004 Share Posted January 4, 2004 Techron from Chevron is avalible from auto parts stores, and it's the sh_t. Also, your higher tier gas stations (Mobil, Chevron, Amoco) use the same amount of additives in their regular octane gasolines as in the premiums. So you get the same amount of cleanliness with your lower octane. I like chevron, although my s-10, which is the only reliable vehicle I have right now, would probably run off of piss. Link to comment Share on other sites More sharing options...
beauregaardhooligan Posted January 4, 2004 Share Posted January 4, 2004 "I want scientific proof - not demostrations" A demonstration *is* scientific proof, bring a stopwatch. "- write a paper and submit it to a journal" Don't believe everything you read. I can write down anything I want, that doesn't make it true. "- how many degrees do you have in physics and chemistry? mechanical engineering perhaps? These are the people I will believe. Maybe you and all the guys who get 100+ MPG from their special carburetors can get together and come up with some degrees in these fields....." Now you're just trying to be mean. "99.9% of all the information in the world is availible ONLY in written form" Say what? Where do you get that from? " - learn to love it AND use it..... Leaded fuel was availible here in the early 80's. Maybe not where you live - that I don't know...." Availability of unleaded is irrelevant, you can still get it in northern Michigan. Why do you think they put the nozzle restrictor on my gas tank? It doesn't matter what is used to raise the octane, anyway. Nor does it matter how the rating is determined. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 Don't believe everything you read So why should I believe you over someone with a degree who is also more articulate? It doesn't matter what is used to raise the octane, anyway. Nor does it matter how the rating is determined. That's just ignorance - if you belive what you just said right there, then there is no point for me to continue discussing this further - therefore - you win! I will discuss this matter with you no further. Please - by all means continue to believe whatever you want - makes little difference to me. GD Link to comment Share on other sites More sharing options...
beauregaardhooligan Posted January 4, 2004 Share Posted January 4, 2004 Perhaps I wasn't being clear, but being articulate doesn't make you correct. My point about octane is, it makes no difference what is used make it a higher octane, it is still a higher octane. Also the system by which you rate it doesn't matter. 32 degrees fahrenheit is the same thing as 0 degrees celsius. Call it what you want, it's still the temperature at which water freezes. I'm not going to call you on your ludicrous claim of 99.9% of all info being written down, that has nothing to do with our discussion. I make my claims on experiences I can reproduce. Don't take your ball and go home. Lets talk this out like gentlemen. Link to comment Share on other sites More sharing options...
torxxx Posted January 4, 2004 Share Posted January 4, 2004 good call Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 Now your talking some sense - let me clarify some issues for you: My point about octane is, it makes no difference what is used make it a higher octane, it is still a higher octane. No - because different additives have different side effects - just like takeing medications - some have the same desired effect on you, but different undesireable side effects.... but this is not the real issue anyway. Not even sure how that one came up? Also the system by which you rate it doesn't matter. 32 degrees fahrenheit is the same thing as 0 degrees celsius. Call it what you want, it's still the temperature at which water freezes. Well - your talking about two completely different things - one of which is a linear scale (temperature of water), and the other is actually a combination of two different linear scales averaged together. There are two different octane rating systems, or approaches if you like. One is called MON or Motor Octane Number. To give you some more info on that I just quote: The motor octane rating, referred to as MON (motor octane number), is the best rating to use when selecting fuel for your race or high compression engine. When testing MON, the fuel is heated to 300° F and the intake air is heated to 100° F. The test engine is a single cylinder 4 cycle engine that is run at 900 rpm. Ignition timing is varied with compression ratio. Engine load is varied during test. The other rating system is called RON or Research Octane Number: Known as RON (research octane rating). Tested at 600 rpm with a fixed timing of 13° BTDC. The fuel temp is not controlled at all and the intake air temp is varied with barometric pressure. This is done to covert everything to a SAE standard day, which is 60° F, 0% Humidity, and 29.92 inches barometric pressure. The RON should not be used when selecting fuel for a race or high performance engine. The RON will always be higher than the MON. So as you can see these are really VERY different systems, and as such, you really have no idea what your getting at the pump since the rating there is an average of these two numbers. For any given fuel, there are MANY (infinite actually) ways to achieve any one specific "pump" octane rating. I quote again: This is what you get at the gas pumps. It is average of the RON and MON. It is ok to use this for lower compression street motors, but when you get much over 10:1, you should really pay attention to the MON. The closer the RON is to the MON, the more stable the fuel is. This can be very critical when running 7000+ rpm. Now that said - back in the day there was no such thing as RON - the pump gave you exactly what the MON was - and with the use of tetraethyl lead (basically a liquid form of lead that is very stable), you have much higher "pump" values. This accounts for the FSM claiming 90.... after the ban of lead completely in '86, RON was introduced to help better guage the knock resistance of other additives besides just lead - thus the new "pump" calculation of (R+M)/2.... not a linear scale at all. Now I really am DONE BTW - if I haven't succeded in showing my point with all that, then apparently I'm not a very good teacher, and I'll just shut up. Seriously tho - do the research - read the books - you'll come to the same conclusions. GD Link to comment Share on other sites More sharing options...
torxxx Posted January 4, 2004 Share Posted January 4, 2004 GD you need to change your name to Dr. General Disorder lol Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 4, 2004 Share Posted January 4, 2004 Yeah, yeah - I'm not THAT knowledgable - I know my way around internal combustion is all... (did you know? there IS such a thing as *external* combustion.... ) GD Link to comment Share on other sites More sharing options...
Stupidru Posted January 4, 2004 Author Share Posted January 4, 2004 Hey Mick, how sorry are you for resurrecting this thread? Link to comment Share on other sites More sharing options...
beauregaardhooligan Posted January 4, 2004 Share Posted January 4, 2004 Define it and label it however you want. Put whatever additive in it you want. Bring me your "High" octane and your "Low" octane and I will show you with my car which one runs better. You may save some money with the lower octane, but the performance of the higher rated juice offsets the added cost. It's worth it to me to run a little faster and pull a little harder. Book larnin' is a great thing, but it don't beat practical experience. Have you tried both in your car, with the timing adjusted accordingly? I have. Oh, yeah, external combustion would be called a "fire." A steam engine is an example of an external combustion engine. BTW, ya'll, I would strongly advise against grabbing the garden hose and "running a constant stream of water" into your motor. GDsan, can you define "hydrolock" for us? Link to comment Share on other sites More sharing options...
mcbrat Posted January 4, 2004 Share Posted January 4, 2004 can you say "hi-jack" Link to comment Share on other sites More sharing options...
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