Even if it does, what's the compelling reason to use a more expensive fuel for that .1% of the time I needed it's benefit??
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- Thread starter chckboy5
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Even if it does, what's the compelling reason to use a more expensive fuel for that .1% of the time I needed it's benefit??
More power output for when your at these operating conditions.
For the same reason you can usually downgrade the octane for vehicles that require premium if you're in cool/moist and low load conditions.
I'm sure Mazda spec'd 87 as safe for all operating conditions but that doesn't mean it's always optimal.
Again, for the .1% of the time it's needed there's not a compelling reason to pay the extra cost of premium fuel. Understand too, I'm not conceding any argument that there even IS such a benefit or that it's appreciable... MikeM's arguments seem far more compelling to me. Especially since I can understand the benefits DGI offers designers.
I'd need proof to the contrary. Has anybody monitored OBD-II data while driving to log timing retard under passing/hill climb conditions? Has anybody made dyno runs with/without premium?
This advice is about 40-50 years out of date and applied to all cars in an era in which engines did not "know" what the outside temperature and barometric pressure was.
In the current era, you can run regular low octane fuels in some engines that are designed to run on the ragged edge of detonation by bouncing off the knock sensor. The Skyactiv family of engines is not in this family of engines. Engines designed to do this have complex algorithms designed to "guess" the effective octane of the fuel in your tank and adapt their ignition and fueling maps to suit not only atmospheric conditions but also the octane of fuel in your tank.
The CX-5 is in a class of vehicles that is not so sophisticated. It does everything that more sophisticated vehicles do except try to guess the octane of your fuel, it just assumes it is at least 87 octane and if it detects knock it will throw an error code and go into a conservative fuel/ignition mapping to get you home.
The way to tell which class your vehicle is in is to read the Owner's Manual. If it states a minimum octane, it is in the less sophisticated class. If it states a range of acceptable octanes, but recommends a higher octane, it is in the more sophisticated class. There is zero performance advantage to putting high octane fuel in a CX-5.
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There is never a time when fuel above 87 octane is desirable in a proper functioning CX-5. If it throws an error code and you have a long ways to drive before you get to a qualified service station, it's a good idea to fill up with premium. Otherwise, with no error code, 87 octane will perform just as well as super-duper 93 octane.
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The EPA requires testing to be done with the same fuel specified in the Owner's Manual. In our case, that would be 87 octane.
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- 2014 Mazda CX-5 GT AWD w/Tech
An interesting article somewhat relevant:
http://www.autoblog.com/2015/08/07/95-octane-cars-more-efficient-report/
http://www.autoblog.com/2015/08/07/95-octane-cars-more-efficient-report/
This will not be happening anytime soon because there are too many cars on the road that would have to pay for higher octane but couldn't benefit from it.
For regulatory reasons it makes perfect sense that the EPA would require use of the same fuel as that owners are being instructed to use. The original post, however, said that SAE uses 91 for their testing. Not that I am agreeing they do, I'm just trying to find logic in why they might aside from that implicit in the assertion.
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Sure, of course, the EPA will absolutely abandon a rule just because it adds unnecessary cost for consumers.
Hah. No, they don't care.
But more to the point: higher octane can be achieved with higher ratios of ethanol. All alone ethanol achieves a number of EPA objectives. Not the least of which it's considered a sustainable fuel, helps achieve lower pollution footprint and reduces fossil carbon emissions. So why not use this as a way to advance that agenda?
I bet alcohol powered vehicles will have a significant place in the future but it will take years for the US to get there. We will have a mix of pure electric, pure alcohol and I'm still skeptical of hydrogen powered vehicles making significant headway but we will see. Pure alcohol (95% alcohol, 5% water) is 99-100 octane and it's what every new car sold in Brazil runs on (the older cars run on 85% alcohol, 15% gasoline or ethanol blend with 18%-25% alcohol). 95% alcohol has a number of benefits - zero lead, zero carbon monoxide, just water vapor and CO2.
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And the carbon in the exhaust pipe CO2 is from biomass, and not a fossil fuel, so it's already in the environment and therefore not a contributor to greenhouse gases.
Except this whole rosy scenario only considers the primary emissions impact! Ethanol has to be concocted from the biomass and that generally involves a lot of fossil fueled power generation along the way from farm to tank. If you consider the whole production cycle, the environmental impact is pretty much the same... or maybe worse.
Hydrogen receives the same short-sighted treatment (it's only emissions is water). At least hydrogen COULD be 'clean' if it's production was fueled exclusively from carbon-free energy sources like wind. But we're way far far away from economically generating sufficient energy from wind to power energy intensive industries like hydrogen generation on a large scale.
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The Mazda CX5 makes 184 hp at 5700 RPM. How often do any of you drive your engine at 5700 RPM? The 2.5 L engine has a lot of low-end torque. Even the 2 L four-cylinder engine makes a decent amount of its torque down low. The argument that the CX5 makes less peak horsepower at 5700 RPM is really moot. Most people care about how much power the engine has in the under 4000 RPM range. This is the range that most manufacturers design the torque peak to occur. In case someone does not know, torque is the actual power the engine makes. It is the twisting force that is measured on a dynamometer. Horsepower is nothing more then a mathematic calculation that determines how much work the engine can do. Horsepower = torque x rpm/5252.
Littlebear, you will never win the octane argument unless you can back it up with solid indisputable evidence like testing on a dynamometer in very carefully controlled conditions. So many times people post on here and swear it's true with their heartfelt arguments that are backed up without solid evidence. So many times I've watched guys like Mike M Point out the ridiculousness of your arguments. In the end this puzzle will never be solved because who wants to invest the time and money in an economy SUV designed for families to prove it.
Littlebear, you will never win the octane argument unless you can back it up with solid indisputable evidence like testing on a dynamometer in very carefully controlled conditions. So many times people post on here and swear it's true with their heartfelt arguments that are backed up without solid evidence. So many times I've watched guys like Mike M Point out the ridiculousness of your arguments. In the end this puzzle will never be solved because who wants to invest the time and money in an economy SUV designed for families to prove it.
Good discussion. Looks like that to prevent the knock, SkyActiv engine goes richer then stoichiometric, sometimes a lot. Rich fuel charge lowers the temperature in combustion chamber. There is visible evidence to that- many cars have soot all over exhaust tips, and the engine oil fuel dilusion is evident if the vehicle sees short trips only. I think that Mazda specifies otherwise conservative oil change intervals because of the later.
Some people report less or no soot when using premium gas. The theory is that the ECU does not have to dump fuel in response to the signal from the knock sensor.
Some people report less or no soot when using premium gas. The theory is that the ECU does not have to dump fuel in response to the signal from the knock sensor.
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- Plano, Texas, USA
Brazil has totally different scenario. They have favorable weather and environment to grow sugar cane and use it to produce ethanol cheaply. We grow corn which uses a lot of water and needs heavy government subsidize to produce ethanol.
MTBE is a much better oxygenate than ethanol for fuel which is cheaper and easier to meet the emission standards. It has better blending characteristics and lower volatility. And it can be shipped through existing pipelines. But MTBE is possibly carcinogenic, easy to pollute groundwater and soil, now it requires 1~30 billion dollars to clean up after many years of usage!
Ethanol has caused many issues on gasoline engines especially the corrosion in fuel system. Ethanol is much less efficient, and sometimes even generating more emissions! It was called "Gasohol" when we're living in Iowa. at time it was cheaper due to government subsidization but everybody knew we should stay away from it! Not to mention using heavy government subsidized, corn produced ethanol in the US caused food and feed prices went way up. Growing corn also requires a lot of water. Unless using sugar cane produced ethanol such as in Brazil which has higher energy content than corn produced ethanol, our model just doesn't make sense under current energy policy!
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- Plano, Texas, USA
Absolutely, we need to look at a whole picture! It requires more energy to produce ethanol with the same amount of energy content! Ethanol has very low energy content comparing to gasoline, you do need to burn a lot more ethanol to achieve the same mileage by using gasoline. Like electrical car which has zero emissions, it basically moves the pollution from cars to electrical power plants, which are mainly using coal, oil, and nuclear in the US. Coal power plant is the dirtiest and unfortunately this is the majority in the US! Burning oil is not clean either. Nuclear? You know the problems of handling the nuclear waste and other potential disasters.
We use 10% of corn produced, heavy subsidized ethanol as the oxygenate in the name of clean air which already has driven up food and feed prices substantially. I just can't imagine if we use 95% ethanol to feed automobiles in the US. Corn should be grown to feed human beings, not to feed cars!
iced_theater
Member
I run 85 octane and have never had it knock. Even in 100 degree temperature with my family and luggage in tow going up Parley's canyon in Utah.
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- RDX Aspec Adv.
A lot of the police vehicles where I used to live had dual-fuel, E85 or regular gasoline. I believe this was the Tahoe's. They were retrofitted as such for the city PD. However, after a few years of running E85, engine issues developed, so they were told to run gasoline more often to prevent it. What were the issues? I don't know. I just heard about it from an officer's wife that I worked with who drove one of the Tahoe's.
That said, E85 is very high equivalent octane, and while you need more fuel volume (larger injectors, etc.), you can typically get more power (and slightly fewer MPG) from an E85 conversion. Now, if you increase compression with an E85 conversion (typically you can go up 2-4 points, depending on the motor/design of the combustion chamber), SIGNIFICANT gains can be had. Ethanol conversion was just getting popular in the LSX world when I sold my Z06 back in 2012.
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- RDX Aspec Adv.
KR in these vehicles is top notch, I'm sure. You may well be losing 10-15bhp though.
Sorry but you are just plain misinformed. Government subsidies to ethanol producers ended years ago. Ethanol trades at free market prices and has more BTU's per dollar than pure gasoline. Yes, it has less BTU's per gallon but it's cheaper than pure gasoline. On the other hand, oil and oil products (including MTBE) receive HUGE subsidies, more than ethanol producers ever received, many billions of dollars every year. How does that make you feel to learn you are not only misinformed but are helping others to become misinformed??
Wrong again. It takes almost twice as much MTBE to provide the same oxygenation to gasoline as ethanol takes. Both have less BTU's per gallon but the additional MTBE means the hit to BTU's per gallon is not large. Ethanol has higher octane vs. MTBE as well.
This is one point we agree on and precisely why MTBE has been outlawed in most states. But the fact that you need so much more to achieve the same benefits does not make it a better oxygenate. And how, pray tell, is a $30 billion clean-up cost not a subsidy?
Misinformed again! I've been running 10% ethanol in a whole slew of vehicles over the previous 20 years and have never had fuel tank corrosion issues. Simply not a concern.
Wrong again! Ethanol is a very efficient oxygenate and the whole reason oxygenates are used is to decrease emissions.
This is hilarious! Just like everyone who "knows" a CX-5 will climb hills faster in the summer if you put premium in your tank! LOL!
Pure gasoline receives huge government subsidies. Ethanol subsidies were phased out years ago.
True, except when it rains a lot. MTBE extraction and oil extraction here in the US requires huge amounts of water and this does not diminish at all even if it's rained hard all month.
Considering how misinformed you are, it doesn't surprise me you came to a conclusion that is not supported by the facts. Ethanol is ethanol. Brazilian ethanol has the same energy content as domestically produced corn ethanol.
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