I like to think we r all so friendly because of the minis being way more rare of a car here than most other forum.
... Ha, ha, that's true jonny, and the fact that If you're not nice here, nobody talks to you... We're like the anti-pirate 4x4. I hate that site. I might troll but never post, you get your A-hole torn out just for saying "HI"... Wedge, I disagree with you!!! Ha, ha, naw...it depends on a lot of stuff. W5, well I like the show. I don't always agree with their conclusions, but I like the topics and the information that they uncover. As far as the octane question, well, you gotta consider a lot of stuff; like what are you trying to achieve? I run 91 in my mini, but that's because I'm boosting. If we're just considering a MPG gain, in any engine, then yes, my opinion is that you will get better millage BECAUSE you can/have-to change the timing to set max-power, pre-ping. In older engines, this is manual, the newer, automatic adjustment by the ECM/ECU. AND, more power (per liter burned) means better MPG. Highway, 80KPH with 87. Now change to 97, change the timing, more power. Same highway, 80KPH, more power to do the same work. The same work done, means less power, means less throttle position, means more vacuum, means less fuel flow, means better MPG... ALSO, I want to cover your increase in heat concept. Talking practical over theoretical. An increase in power, with a decrease in heat...is referred to as an increase in efficiency. What we're talking about here, is an increase in efficiency, to gain the increase in power. Not the other way around. NOW, if we consider the concept based on COST alone...I don't know, I've never made the calculations. The cost of premium VS the cost of basic, with the timing/efficiency changes. In a comparative ratio to the actual MPG. Could you save money by switching to a high octane fuel, and adjusting your timing in a classic car. OR, just letting the ECM do it's thing, in a modern car? Are you in Denver, driving a Prius, or in Florida, driving a winnebago? Conclusion: you gotta do the work to figure out if this is right for you, what you have, and what you are doing with it. For me, well I like the power gain in the boosted 0.657 liter F6A @ 7PSI. So yea, I'm running 91, with the timing adjustment, and that's right for me. We've moved on, to the Somender Singh question. Which is considered as "free octane". A simple concept, but just might save the average guy some $, because it's free. Higher efficiency for a given octane rated fuel. I run meth above 15 degree C ambient, so, this is interesting to me, and could potentially eliminate it's need, or even up the given power with additional timing adjustment and operational considerations. This is just what's right for me, and mine. AND, my opinions. I had found the holly grail site of Somender Singh, from some month ago. I'll see if I can't find that again. May be interesting to some. Fupa's off on his own, so we'll wait till he's done. Dissertation switch....OFF ...op: PS, This thread's been hijacked to hell, but, guess it's all still related to millage. Hope Starpuss doesn't mind...
Man, I don't know what's up, but more and more often, I have to go "cashed"...have a look around... http://webcache.googleusercontent.c...gh/+www.herningg.com&cd=5&hl=en&ct=clnk&gl=ca
This what I have read and learned so far. The only thing octane rating is, is resistance to detonation and heat. The higher the octane, the more heat required to get the mixture to ignite. Hence the reason cars with higher compression engine or turbos require premium. Cars with turbos, etc, and with higher compression tend to have their mixture get much hotter in the combustion chamber before the ignition spark. Using a lower octane gas in a car that requires premium causes premature detonation which is bad since the heat detonates the lower octane gas. Likewise, if you are using higher octane gas in your car, the mixture may not get hot enough in your combustion chamber to burn completely through. This leaves excess fuel/air mixture in your combustion chamber during the exhaust stroke, causing a loss of power and buildup of excess contaminants. Stop using high octane on non high comp or turbo/SC engine, because you're losing power and you're throwing money away. This also burns your valves and over time you will burn through them. As for using high octane gas and nitrous, this is somewhat a paradoxical situation. Nitrous can benefit from using higher octane gas, since the oxidization process induced by nitrous causes the mixture to super heat. again higher octane gas is more resistant to heat, therefore will help prevent detonation when spraying.however, when you're not spraying, you're back into the category above, where it's causing loss of power and excess waste and contaminants. Methanol is completely different than using pump gas. You can't even compare the two. No, higher octane gas does not burn more cleaner, nor does it burn more completely. All the octane rating means is that it is more resistant to detonation and heat. And as for the person who got better mileage with 89 than 87. Assuming your car isn't FI'd then you did NOT get better mileage just because you used higher octane. There are too many other factors involved to do an experiment like that. The only case where this would be is if your car was detonating for some reason, but you'd get a CEL if something was that majorly wrong .Also, the whole "well premium gas has more cleaners in it to help your car". wrong. government regulations prevent this. the only difference is the additive used to increase octane rating. Once again. Higher octane gas is more resistant to heat and detonation. (this also means it takes longer to burn, which is WHY if you DONT have a car set up for premium you'll eventually burn through your valves). If you are going to run premium you have to tune for premium. you would have to advance your timing 2 degrees and retard your exhaust valves in order to allow the mixture to burn through completely before the scavaging of the chamber. As for using 100 octane gas in your car, I'd advise against that in a very cautious sense. The additives in higher octane gas worsens the effect you're seeing here, even if you're using nitrous. Turbos can use it if they crank up their boost to the point that they'd benefit from it. However, most don't do that unless they've been tuned for it, because running high octane gas and high boost without being tuned is a very dangerous combination to gamble with. Oh and I found out the thing with the injectors. The additive that they use to give gas its higher octane can cause premature injector failure, injector misfires, etc, if your injectors were not made for that kind of fuel. This is an extreme case and few and far between, but it can happen, and does happen. I have to go back and look, but the additives cause buildup on the injectors, leading to the above said failures. However, this is not always the case, so really, it's hardly worth mentioning. This was in a pdf i found at the american petroleum institute. here are some excerpts. i believe this was also hilighted on the service advisor web site. WHAT IS OCTANE RATING? Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions. I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK? It did in older engines using carburetors to regulate air/gas mix they cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution. 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. Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only. 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. DOESN'T HIGHER OCTANE GASOLINE HAVE MORE CLEANING ADDITIVES THAT ARE GOOD FOR MY ENGINE? No .US Government regulations require that all gasoline contain basically the same amount of additives to clean the injectors and valves. The only differences are the type to help create the different octane ratings. All gasoline burns at the same rate, it is the additives that create the different octane ratings for the different types of engines. http://auto.howstuffworks.com/question90.htm And here's from the federal trade commission. http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm Cars that do not have higher compression have a lower temperature of the mixture before ignition. (this is basic physics... the more you compress air/matter the hotter it gets) So in a car that does not have higher compression,for exemple honda builds cars from the factory with the appropriate timing for the recommended octane. Higher octane gas burns LONGER since it is more resistant to detonation and heat. So the time it takes to burn through the mixture on 87 octane is LESS than what it takes to burn through a mixture with 93 octane if your car is setup for 87 octane (like the civic) the 93 octane will not have completely burned through the mixture by the time your combustion chamber has opened the exhaust valves and is scavanging the mixture. This gives the still burning mixture the not-so-great opportunity to burn through your valves since it now has an out and a re-introduction of oxygen via the open exhaust valves. This is what causes the buildup of crap on your valves and other parts which can lead to damage down the road. Also because the mixture did not finish burning, some of that fuel or unburned mixture can go through your exhaust and then settle in your catalytic converter if equiped, causing you to fail emissions and/or damage your cat. So there are 2 keys to having a car that can run premium effectively without these issues. number 1, higher compression, which causes more heat, allowing the mixture to burn more efficiently and more thoroughly with less leftover contaminants. Number 2, advanced ignition timing and retarded exhaust valve timing, allowing the mixture more time to burn with closed valves going from 87 to 89 octane isn't too bad, but going from 87 to 93 can be harmful in the long run and cause a loss of power in the short run. (if your mixture burns all the way through, it gives you more power obviously) like in your S/C spaner. Just for the record, octane rating is this: pure iso-octanol (the harder to get of the two forms of octanol) is considered to have an octane rating of 100. 87% iso-ocatanol and 13% n-octanol has an octane rating of 87. Every other compound is then measured agianst 100% iso-octanol, for instance methanol, has an octane rating of 104, so it is 104% harder to ignite than iso-octanol. You see this has little to do with carbon build up. Really it is more like the additive they put in to the fuel, try changing gas stations. But from what I have seen of other peoples pistons, it isn't abnormal. What a company can do is take a low grade fuel, like say 80 octane octanol, and mix 5% methanol like Sonic stations (which has an octane rating of 104) and get 87 octane. These addative have are more likely to cause carbon build up. Some of these addative are to raise the octane while other are for the enivroment. Also keep in mind, methanol is bad, not for your engine but for all the plastic lines and O-rings, Shell uses methanol in their gas. This is text book stuff, yes I seen those text books. In the end, just use what gas your manual cars for. Detergents are nice, but your car doesn't require them to run nor will they give noticable power or anything of that nature nor will they clean you engine more (well maybe a little, but you'll never notice the difference). This is all I have so far on octane sorry it was long. Disertaiton switch off
Information bomb. A little much in one go but I read through it all and I appreciate you taking the time to share. I agree with a lot of that, strangely, the most important consideration factor was not mentioned though. Density Altitude. Ambient temperature and pressure. Touting the benefits of the EFI negates it's consideration maybe, but not its' inclusion and understanding. It's the biggest factor. The benefit to the study of, is consensus of the subject. Eventually... Back to the original question though. Can you get better millage by running higher octane rated fuel? Perhaps a more meaningful answer would come from a better worded question. Can you get better millage from working with higher octane rated fuels?
