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Car Forum / Honda Cars / June 2005Which Gasoline Grade is Best for Honda Hybrid 2005?
Hello! I recently bought a Honda Civic Hybrid 2005 and its User Manual says that "Gasoline Grade should be 86 or higher", which means any grade above 86 which could be "Regular 87", or "Mid-Grade 89" or even "Premium 93" can be used, as I understand. If I use "93 Grade Gasoline", will it do any harm to the engine? What are the pluses and minuses in using the "93 Grade"? What would you recommend and why? I thank you for your time and will appreciate your advise. Regards, SG > Hello! > [quoted text clipped - 9 lines] > Regards, > SG Just use the "Regular 87". Using higher octanes won't harm the engine, but it will definitely harm your wallet. > Just use the "Regular 87". Using higher octanes won't harm the engine, but > it will definitely harm your wallet. Higher octane fuel, in fact, will lead to *less* gas mileage for that car. >>Just use the "Regular 87". Using higher octanes won't harm the engine, but >>it will definitely harm your wallet. > > Higher octane fuel, in fact, will lead to *less* gas mileage for that > car. not necessarily. depends how smart the engine management system is. in the "old" days before knock sensors and crank angular velocity measurement, igniton timing had a fixed map. with the above sensors, you have a base map, but also an algorithm that monitors these two other factors and from that, it can calculate in real time a set of new ignition characteristics to take maximum advantage of any particular fuel. i would hope that the expensive "super econo" car's management would be this smart. > > Higher octane fuel, in fact, will lead to *less* gas mileage for that > > car. [quoted text clipped - 7 lines] > fuel. i would hope that the expensive "super econo" car's management > would be this smart. No, it has no need to do any such thing. It is designed to operate on 86 octane fuel. It has no need to "take advantage" of anything else. >>>Higher octane fuel, in fact, will lead to *less* gas mileage for that >>>car. [quoted text clipped - 10 lines] > No, it has no need to do any such thing. It is designed to operate on > 86 octane fuel. It has no need to "take advantage" of anything else. but formulations change between producer, by country, by state, by season, by law, by mistake... there's plenty of reason to use smart management, and a by-product of that is being able to run any grade gas to best advantage. > but formulations change between producer, by country, by state, by > season, by law, by mistake... there's plenty of reason to use smart > management, and a by-product of that is being able to run any grade gas > to best advantage. no, the *only* thing it has to do is prevent engine damage from knocking. You don't program it to run any grade at that grade's best advantage. For example, where does that stop? Can I put avgas into my Hybrid and the programming will "take advantage" of that? It's designed to run at 86 octane. Yes, the engine management computer will prevent damage should lower octane fuel be present, but that's different from saying it will change the engine parameters for more performance if higher octane is present. It doesn't do that. >>but formulations change between producer, by country, by state, by >>season, by law, by mistake... there's plenty of reason to use smart >>management, and a by-product of that is being able to run any grade gas >>to best advantage. > > no, the *only* thing it has to do is prevent engine damage from knocking. there's more to gas than octane rating. > You don't program it to run any grade at that grade's best advantage. > For example, where does that stop? Can I put avgas into my Hybrid and > the programming will "take advantage" of that? modern programs run each tank of gas according to each engine sensor's output and how that complies with what the ecu knows it can do with it. if its ability to read sensor results for avgas are within its abilities to manage, then sure, it can run avgas to best advantage. if it can't, it won't and i'm not trying to tell you i know how the thing is programmed. > It's designed to run at 86 octane. Yes, the engine management computer > will prevent damage should lower octane fuel be present, but that's > different from saying it will change the engine parameters for more > performance if higher octane is present. > > It doesn't do that. i'm not interested in a personal disagreement - i'm only interested in the technology. i've stated what what i understand to be the current state of the art, and that /does/ include ability to run different grades of gas to best advantage. i'm /assuming/ this applies to the honda because honda have the necessary sensors, ie. knock and crankshaft angular velocity, [among others]. and they have a good mechanical design. other than fuel/air charge & ignition, one other big thing in the performance equation is combustion chamber design. basically, some designs can only run well with high octane. honda otoh have a design that fundamentally runs well with lower octanes, but burns higher octanes very well too - something that's hard to do well the other way around. from that perspective, the honda /should/ be able to take best advantage of different grades if it's getting the necessary ecu input and has sufficient "smarts" to handle it, hence my assumption. but maybe you /know/ this is not the case. > i'm not interested in a personal disagreement - i'm only interested in > the technology. i've stated what what i understand to be the current > state of the art, and that /does/ include ability to run different > grades of gas to best advantage. The state of the art is that yes, that can be done. Does any car company engineer that into its low end family car? No. > > i'm not interested in a personal disagreement - i'm only interested in > > the technology. i've stated what what i understand to be the current [quoted text clipped - 5 lines] > > No. For Honda, yes. It's not a matter of the ECU adapting to the fuel. It's a matter of having simple feedback systems in key areas. Honda knows how to make simple and efficient ECUs like nobody else. That said, octane doesn't change performance unless the ECU is retarding the ignition and recirculating exhaust gas to avoid knocking at wide open throttle. The HAH does it all the time at low throttle but who cares? Exhaust gas recirculation is just as good as more octane for low throttle. >>>Just use the "Regular 87". Using higher octanes won't harm the >>>engine, but it will definitely harm your wallet. [quoted text clipped - 3 lines] >> > not necessarily. depends how smart the engine management system is. Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs of energy by volume than lower octanes.  SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>>>Just use the "Regular 87". Using higher octanes won't harm the >>>>engine, but it will definitely harm your wallet. [quoted text clipped - 6 lines] > Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs > of energy by volume than lower octanes. other way around, according to my bosch automotive handbook at any rate. there, regular gasoline is rated at 42.7MJ/kg vs. premium at 43.5MJ/kg. at 1.054kJ per btu, that's... > > Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs > > of energy by volume than lower octanes. > > > other way around, according to my bosch automotive handbook at any rate. Your handbook is wrong. >>>Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs >>>of energy by volume than lower octanes. >> >>other way around, according to my bosch automotive handbook at any rate. > > Your handbook is wrong. maybe, but the bosch automotive handbook has been an industry standard for nearly 30 years. if it /is/ wrong, you really need to write & tell them. in addition, http://www.chevron.com/products/prodserv/fuels/bulletin/fuel_economy/ contains the passage: "On average, the heating value of premium-grade gasoline is about 0.7 percent higher than regular-grade because premium-grade, in general, contains more aromatic hydrocarbons — the class of hydrocarbons with the highest densities." admittedly, that's not a lot, and chevron go on to say that the consumer cannot tell the difference, but the principle applies. it's also [engineering] ballpark with the bosch figues which show a 1.8% differential. in either case, the difference does not justify the cost increment. in looking for that reference, i was surprised how hard it was to find references to btu ratings for gasoline, because when you buy natural gas, it's rated in btu's per cubic foot so there's no "black magic" on what you're getting for your money. with gasoline, that information is all but absent. i find that extroardinary because there's really /no/ reason it can't be smilarly rated. except perhaps that it would make oil companies more accountable... for california residents, there's also this little nugget: http://www.chevron.com/products/prodserv/fuels/bulletin/oxy-fuel/enrgycon.shtml great. even less bang for the buck. >>>>Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs >>>>of energy by volume than lower octanes. [quoted text clipped - 37 lines] > >great. even less bang for the buck. Well you had to know that throwing some oxygen into the mix wasn't going to give you more energy. Pre-burned fuel, what a marketing concept. >>>>>Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs >>>>>of energy by volume than lower octanes. [quoted text clipped - 41 lines] > going to give you more energy. Pre-burned fuel, what a marketing > concept. One of my great laughs was a few years ago when a drink salesman was at my local deli and was pushing "Sports Water", i.e., water with extra O2. I asked the guy how he differentiated it from hydrogen peroxide & got a bovine stare. >> Actually, Elmo's assertion is correct. Higher octane fuels have fewer >> BTUs of energy by volume than lower octanes. [quoted text clipped - 3 lines] > there, regular gasoline is rated at 42.7MJ/kg vs. premium at > 43.5MJ/kg. at 1.054kJ per btu, that's... That's an error. Google for it. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>> Actually, Elmo's assertion is correct. Higher octane fuels have fewer >>> BTUs of energy by volume than lower octanes. [quoted text clipped - 7 lines] > > Google for it. I just did some digging of my own to be sure. Basically, the energy content is the same between different octane ratings of gas...UNLESS...oxygenates have been used. Oxygenates (alcohols, ethers) reduce the energy content of the fuel mixture because they introduce more oxygen into the mix. As the O2 sensor responds to the increased oxygen content, the engine management system will increase fuel delivery to compensate, hence lower gas mileage. This from the Gasoline FAQ and from Wikipedia. www.repairfaq.org/filipg/AUTO/F_Gasoline2.html http://en.wikipedia.org/wiki/Gasoline I've noticed through extensive record keeping that my Integra will deliver an average of 2% lower gas mileage with 91 octane versus 87. The 91 octane I use has no oxygenates, and yet I still get a fuel mileage reduction. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>>>Actually, Elmo's assertion is correct. Higher octane fuels have fewer >>>>BTUs of energy by volume than lower octanes. [quoted text clipped - 10 lines] > I just did some digging of my own to be sure. Basically, the energy content > is the same roughly the same. > between different octane ratings of gas...UNLESS...oxygenates > have been used. [quoted text clipped - 3 lines] > to the increased oxygen content, the engine management system will increase > fuel delivery to compensate, hence lower gas mileage. i'm not sure about that. the sensor knows no difference. all it does is measure stoichiometry through electrode potential. more likely the extra fuel delivery comes from the driver having to use more throttle to get the same performance rather than the ecu injecting more for any given throttle setting. > This from the Gasoline FAQ and from Wikipedia. > www.repairfaq.org/filipg/AUTO/F_Gasoline2.html [quoted text clipped - 3 lines] > an average of 2% lower gas mileage with 91 octane versus 87. The 91 octane > I use has no oxygenates, and yet I still get a fuel mileage reduction. don't think the ecu on your vintage integra is "smart" enough to cope. afaik, it has no knock sensor & no angular velocity measurement. i read about half of that wiki, and had the impression that the energy yield question was not being directly answered. either it's a question too hard to answer [which i doubt] or it's just not convenient to have an easy comparison yardstick available to consumers. imo, that's the central point of this discussion. just like weights & measures stickers that are put on every gas pump in the country to avoid fraud by local merchants, i see no reason why gas companies shouldn't publish btu ratings for their gasoline. >> Oxygenates (alcohols, ethers) reduce the energy content of the fuel >> mixture because they introduce more oxygen into the mix. As the O2 [quoted text clipped - 3 lines] > > i'm not sure about that. the sensor knows no difference. It senses oxygen. Octane enhancers that work by adding oxygen to the mix increase the oxygen octane content of the exhaust. The O2 sensor responds precisely the way it's supposed to, producing lower voltage for the ECU to see. The ECU responds by dumping more fuel in until it sees what it expects to be the correct voltage from the O2 sensor. > all it does > is measure stoichiometry through electrode potential. more likely the [quoted text clipped - 13 lines] > don't think the ecu on your vintage integra is "smart" enough to cope. > afaik, it has no knock sensor & no angular velocity measurement. You're right. I cannot explain why I see that difference. It's pretty consistent, too. > i read about half of that wiki, and had the impression that the energy > yield question was not being directly answered. either it's a > question too hard to answer [which i doubt] or it's just not > convenient to have an easy comparison yardstick available to > consumers. Wikipedia is not made by the oil companies. Anybody can contribute. I suspect it's either a complicated subject, or it's too simple to be worth bothering with, which is what I get from the Gasoline FAQ. > imo, that's the central point of this discussion. just > like weights & measures stickers that are put on every gas pump in the > country to avoid fraud by local merchants, i see no reason why gas > companies shouldn't publish btu ratings for their gasoline. Maybe because nobody would care or understand, or it would cause confusion. Notice how many BTUs there are in diesel? Makes gas look pretty bad. SignatureTeGGeR® The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ >>>Oxygenates (alcohols, ethers) reduce the energy content of the fuel >>>mixture because they introduce more oxygen into the mix. As the O2 [quoted text clipped - 9 lines] > see. The ECU responds by dumping more fuel in until it sees what it expects > to be the correct voltage from the O2 sensor. but it measures unburnt oxygen. the "oxygen" in oxygenated fuels is supposed to be consumed in preference to molecular oxygen from the air, not be sensed as exhaust content. as i understand it, all that's happening is that for any given mass of gas, proportionately less of it is H-C available for combustion, hence the need to be more heavy footed. >>all it does >>is measure stoichiometry through electrode potential. more likely the [quoted text clipped - 16 lines] > You're right. I cannot explain why I see that difference. It's pretty > consistent, too. sorry, i should have gone on to say that the reason this happens is that the slower burn rate of the higher octane requires more advanced ignition timing. if the ecu's only got a fixed map of timing, as is the case here, it won't compensate. if you want to run high octane, you can manually advance the base timing setting to get your economy back. >>i read about half of that wiki, and had the impression that the energy >>yield question was not being directly answered. either it's a [quoted text clipped - 5 lines] > suspect it's either a complicated subject, or it's too simple to be worth > bothering with, which is what I get from the Gasoline FAQ. right you are, but my point is that the contributors all seem to have a common mantra. whether that's a product of a common oil company background or not, i can't say, but wikipedia is not a question forum making it hard to ask the dumb questions, and i don't see answers to my dumb question! >> imo, that's the central point of this discussion. just >>like weights & measures stickers that are put on every gas pump in the >>country to avoid fraud by local merchants, i see no reason why gas >>companies shouldn't publish btu ratings for their gasoline. > > Maybe because nobody would care or understand, or it would cause confusion. if they don't care or understand, that's ok. i bet most people don't care much about weights & measures stuff either. the point is that if you /want/ to care, you can't. > Notice how many BTUs there are in diesel? Makes gas look pretty bad. that's a good reason to use diesel and part of the reason why diesel offers better mileage, [the other main reason being better thermodynamic efficiency]. >>>>Oxygenates (alcohols, ethers) reduce the energy content of the fuel >>>>mixture because they introduce more oxygen into the mix. As the O2 [quoted text clipped - 15 lines] >happening is that for any given mass of gas, proportionately less of it >is H-C available for combustion, hence the need to be more heavy footed. Except that, your right foot doesn't control fuel, it controls air. The ECU controls fuel based on the incoming air mass which is determined directly (through an air mass meter of some sort) and/or imputed from various factors such as throttle position, rpm, manifold absolute pressure, outside air temperature, etc. The O2 sensor is part of the feedback loop telling the ECU whether it's calculation was correct. If the ECU assumes pure HC fuel is being injected when the fuel is oxygenated, it will not inject enough fuel to consume all of the oxygen taken in by the engine. The O2 sensor will detect this excess oxygen and the ECU will inject more fuel in the next cycle to compensate. You don't notice any loss of power because there isn't any. Therefore, you don't push harder on the pedal, you just pay more at the pump. >>>all it does >>>is measure stoichiometry through electrode potential. more likely the [quoted text clipped - 55 lines] >offers better mileage, [the other main reason being better thermodynamic >efficiency]. >>Just use the "Regular 87". Using higher octanes won't harm the engine, but >>it will definitely harm your wallet. > > Higher octane fuel, in fact, will lead to *less* gas mileage for that > car. IIRC the V6's will do better on premium petrol. They include sensors to notice the reduced tendency to knock & will optimize timing to take advantage of it. (been discussed previously on this NG) The 3L V6 on the regular Accord will gain about 10HP (according to a Honda engineer) with premium, so I don't see why this one shouldn't. It's essentially the same engine, more or less, and both produce 240HP. > > Just use the "Regular 87". Using higher octanes won't harm the engine, but > > it will definitely harm your wallet. > > Higher octane fuel, in fact, will lead to *less* gas mileage for that > car. On the flip side, we just came back from a 4,000 mile trip, and I could see about a 2 mpg drop in mileage when using the 85 octane at 3-pump stations. They are usually 85, 88 and 91 octane. I try to avoid 3-pump stations as the 88 octane, which we really need (car requires 87), is significantly higher priced than the 85 octane or the 87 octane at 2-pump stations. 2003 Accord V6. Dick >The 3L V6 on the regular Accord will gain about 10HP (according to a >Honda engineer) with premium, so I don't see why this one shouldn't. [quoted text clipped - 5 lines] >> Higher octane fuel, in fact, will lead to *less* gas mileage for that >> car. > Hello! > [quoted text clipped - 9 lines] > Regards, > SG They'll all run the same so go for the lowest octane from a station that sells fresh and clean gasoline. Older cars are more sensitive to the octane rating. Their air-fuel/emissions systems are operated by mechanical vacuum controlled valves that are out of adjustment without sea-level air pressure behind them. You had to reduce the octane at high altitudes to compensate for the extra EGR and retarded ignition timing. Newer cars use several feedback systems so that the engine runs at its best under a wide range of conditions. >Hello! > [quoted text clipped - 4 lines] >Gasoline", will it do any harm to the engine? What are the pluses and >minuses in using the "93 Grade"? What would you recommend and why? Using 93 will do no harm to your engine, but it will lighten your wallet. Just use regular and pocket the savings. ----------- Alex |
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