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Jacky
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I was reading about the 2012 Civic Si this morning and noticed that it requires premium unleaded (cha ching), which seems like a strange requirement to me. Had anyone just used regular unleaded in their Si and noticed any issues?
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A77
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I think it is recommended - not mandatory. using lower octane will worsen performance and gas mileage a bit. Pony up - at the end of the day how much extra does it really cost? a coupe of hundred a year? excluding better mileage.
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DCR
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Jacky wrote:
I was reading about the 2012 Civic Si this morning and noticed that it requires premium unleaded (cha ching), which seems like a strange requirement to me. Had anyone just used regular unleaded in their Si and noticed any issues?
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Engine compression. If you search around, you'll see multiple threads on multiple forums about running regular gas in an Si. You can experience knocking, reduced MPG, etc, but I can't tell you first hand because I never put regular in mine and wouldn't.
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owequitit
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Jacky wrote:
I was reading about the 2012 Civic Si this morning and noticed that it requires premium unleaded (cha ching), which seems like a strange requirement to me. Had anyone just used regular unleaded in their Si and noticed any issues?
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Premium has been recommended for the Si for a long time now. Not sure what the big deal is, I figured it out for 12,000 miles a year and the difference is about $120. If the $120 is that important to you, then there is no reason to opt for the Si.
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kidoairaku
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since 2006 the Si's have been premium.
The 06 SI running on Regular made the fuel efficiency drop like mad and the car felt terrible. it was never worth it to cheap out and avoid premium gas.
In Toronto Canada, 18000 km per year, difference in cost is over $250 for premium gasoline.
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JeffX
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owequitit wrote:
Jacky wrote:
I was reading about the 2012 Civic Si this morning and noticed that it requires premium unleaded (cha ching), which seems like a strange requirement to me. Had anyone just used regular unleaded in their Si and noticed any issues?
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Premium has been recommended for the Si for a long time now. Not sure what the big deal is, I figured it out for 12,000 miles a year and the difference is about $120. If the $120 is that important to you, then there is no reason to opt for the Si.
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here, premium is $0.30/gallon more than regular (some stations it's still only $0.20/gallon more, but none in my immediate area), and on average I run 2 tanks a month through my Si, and it's usually right at 10-11 gallons per fillup. So I'm looking at a price premium of $6.00 to $6.60 per month. If you double what I'm doing in terms of mileage, that works out to about 1100-1200 miles per month, 4 tanks, and a $12.00 to $13.20 monthly premium. I don't ever sweat it. I can't remember the last time I spent over $40 filling up my car. I know it's happened once or twice when it went over $4/gallon but it's been a long time.
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owequitit
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Jeff wrote:
owequitit wrote:
Jacky wrote:
I was reading about the 2012 Civic Si this morning and noticed that it requires premium unleaded (cha ching), which seems like a strange requirement to me. Had anyone just used regular unleaded in their Si and noticed any issues?
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Premium has been recommended for the Si for a long time now. Not sure what the big deal is, I figured it out for 12,000 miles a year and the difference is about $120. If the $120 is that important to you, then there is no reason to opt for the Si.
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here, premium is $0.30/gallon more than regular (some stations it's still only $0.20/gallon more, but none in my immediate area), and on average I run 2 tanks a month through my Si, and it's usually right at 10-11 gallons per fillup. So I'm looking at a price premium of $6.00 to $6.60 per month. If you double what I'm doing in terms of mileage, that works out to about 1100-1200 miles per month, 4 tanks, and a $12.00 to $13.20 monthly premium. I don't ever sweat it. I can't remember the last time I spent over $40 filling up my car. I know it's happened once or twice when it went over $4/gallon but it's been a long time.
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We run about $.20 more out here. I figured a $.20 premium at 15,000 annual miles, and 30MPG. I came up with $100, so figuring that I get better than average MPG, I added 20% to be safe.
The other thing I don't think most people consider is that as gas prices rise, the price premium for premium unleaded remains fairly constant, which actually decreases the cost difference as a %.
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RocketRon
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Dear Poster,
The engine in your Civic SI has a compression ratio of 11:1. This means that you are the proud owner of a performance engine that actually gives you a benefit for using premium.
Enjoy this performance advantage or get a regular Civic that uses regular gas.
I won't waste any time explaining the potential damage that could occur...
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CB77
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Most oil industry experts say that new cars have their engines so well monitored and controlled by computers, that there is no problem running 87 octane in any engine. You will see a slight HP decrease and a very slight MPG decrease...but you will come out far ahead, $/wise. Here is an article by one of these experts:
Before the switch to fuel injection and computerized controls, engines were subject to damage from prolonged knocking. But today’s engine management systems incorporate electronic knock sensors, which detect the condition and adjust the ignition to stop the problem. As a result, it is almost impossible to hurt a current engine by using 87-octane fuel, industry experts say.
“Modern engines prevent the damage from happening before it starts,” said Patrick Kelly, a fuels analyst with the American Petroleum Institute. “It wouldn’t impact fuel economy. And it wouldn’t impact the emissions. What it would impact is the performance.”
Of course, owners who do not heed the automakers’ recommendations may face consequences — the potential voiding of warranties, for instance. But for the most part, manufacturers’ fuel recommendations include some wiggle room.
Porsche, for example, acknowledges that any of its modern production cars can be run on regular fuel without the risk of damage.
A spokesman for Porsche North America, Tony Fouladpour, added a caveat. “If you want the car to perform at its maximum capability, the best choice would not be 87,” he said. “But we do not forbid it.”
Specifying premium fuel lets a car manufacturer squeeze out more horsepower. BMW, for example, recommends that all the cars it sells in the United States use premium fuel, but they will run on regular.
“There generally isn’t any harm done to the engine by using lower-octane fuel,” said a BMW spokesman, Thomas Plucinsky. “Because our engines do have very good forms of knock sensing and are able to deal with lower-octane fuels, you will not have any drivability issues. You will, however, lose some of the performance.”
How much of a loss? Some indication can be found in the peak horsepower numbers Hyundai recently released for its new Genesis sedan. On premium, the 4.6-liter V-8 engine is rated at 375 horsepower. On 87-octane regular, it is 368.
That seven-horsepower difference — less than 2 percent — seems a small penalty for saving 30 cents a gallon, especially when you can regain that performance simply by filling up with premium.
Does using lower-octane fuel reduce mileage or increase emissions, as some drivers believe? Not according to the Environmental Protection Agency. “E.P.A. fuels engineers say that there isn’t a meaningful difference between regular and premium gasoline,” said Dale Kemery, a spokesman for the agency.
Still, the warning from some automakers can give an owner pause at the pump. The manual for the Smart Fortwo repeats the warning issued for other vehicles sold by Mercedes-Benz: “To maintain the engine’s durability and performance, premium unleaded gasoline must be used.”
But even those stern words may have some room for interpretation. Dave Schembri, president of Smart USA, told John Schwartz, a reporter who was writing for this section’s blog about his experiences in buying a Smart, that he should not worry.
“You could use regular gas — there’s no damage to the car,” Mr. Schembri said.
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Jacky
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CB77 wrote:
Most oil industry experts say...
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Thanks for sharing that information.
I appreciate everybody else's input as well.
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RocketRon
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Performance wise, according to one estimate, a car running on regular unleaded instead of premium will take about a half a second longer to accelerate from zero to 60 mph (97 kilometers per hour).
Adding half a second to your SI's performance somewhat defeats the purpose of paying an extra 5k over a regular Civic...Just saying
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notyper
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The problem is that no one has actually implemented a _predictive_ knock control system (although Saab has demonstrated one by measuring ionization potential between the spark plug and piston - very cool). They are all _reactive_. That means that when you put 87 octane into a car designed to run on 91 octane, it must actually knock before it can start pulling timing out. Knock is a massive pressure spike in the cylinder that is akin to hitting the piston, rings and valves with a hammer. These components can only take so many of these impacts before something fails. Every time you have a knock event, you're one step closer. If you want to play that game, that's your problem of course, but you've been warned.
Additionally, running lower octane requires a reduction in ignition timing. This reduces not only power, but efficiency. The qutoes some automakers make for power reductions don't tell you the whole story either. While a peak value may be down slightly, you may find you're down upwards of 10% output other areas of the curve. On the mpg front, some small turbo motors suffer greatly when run on lesser octane. In particular the new Chevy turbos actually run a lower cost per mile on premium thanks to improved performance and economy when running 91+
Oh yes, almost forgot. Due to the fact that a knock sensor is just a narrow band microphone, it becomes more and more difficult to filter out other engine noises as rpms climb. Because of this, many automakers either turn off knock sensing at high rpm (Nissan VQ motors, above about 5500 rpm, Subaru turbo-4s above 6000 rpm) or desensitize the knock sensor so much (Honda) that it is far less effective. Thus, you're counting on the engine computer to calculate the effect of the octane you're running by sensing knock at lower rpms and apply a reduction in timing at high rpm based upon an algorithm. So you're no longer even sensing knock, just guessing what it takes to eliminate what you _think_ might happen (I guess that is a bit predictive, but not in the way you'd like IMO).
SC
Last edited by notyper on 03-06-2012 11:38
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poweredByHonda
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Several years ago, a moderator in the Acurazine TSX forum ran a comparison with his TSX, using 87 and 91 octane gas.
check it out here..
http://tsx.acurazine.com/forums/showthread.php?t=659399
since it is real world driving, and not in a controlled lab environment, your distances will vary............
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cforez
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Is it possible to come at the problem the other way and set the base timing to work with regular unleaded and advance the timing if the computer detects 91 octane? Do you lose potential maximum power with 91 or still have problems with knock if you do it this way?
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RocketRon
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Thank you SC for saving me the time it required to explain the potential damage that might occur.
It perplexes me as to why an individual would consider using regular gas on a performance engine with the hope of saving a couple of benjamins annually while risking substantial loss in performance, mileage and longevity?
I guess these types of questions will be common from owners of the 2012 SI, different strokes for different folks.
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notyper
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Nice thought cforez, but you can't do that unless you have the ability to actually detect the octane of the fuel before you combust it (and octane is normally determined with, yep, a single cylinder specialized engine). Here's why:
If you tune the engine on 87 octane, it isn't going to knock under normal conditions. Thus, if you put 91 octane in instead, the way the engine operates is not going to noticeably change, at least in any way that commercial grade automotive sensors will reliably be able to discern.
The only way you can really pick up whether you have higher octane in the tank is to be continuously advancing the timing to the point of knock and then pulling back. If you happen to have 91 octane in, you'll be able to advance further without knock and make more power. But to do so still requires that you get some knock to tell you where you are.
As an analogy, think of trying to find out where a hot stove is in the dark while dressed in a wetsuit with only your hands exposed. You feel around, feel around until 'OUCH!' you touch a burner. Now maybe you'll get lucky and get close without getting burned too bad, but you're gonna have to feel the heat to find it. In the rapid fire world of an combustion chamber, you don't get a lot of time to sneak up to the verge of knock, if for no other reason than the consistency of combustion from one firing event to the next is not sufficient to see a slight increase in cylinder noise that might occur just before knock occurs.
As sensors, engine controls and production methods continue to improve, maybe we'll get to that point.
SC
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cforez
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Ah, I see. I guess the simplest way to do it would be some kind of manual selector where the driver could tell the car the octane on each fill up- the automakers could call it the "lawsuit switch", haha. Mixing grades would be a problem though.
Thanks for the explanation!
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notyper
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Yep, that's what we do with Evos, Nissans (at least those with cruise control) and GM vehicles (requires installing a switch).
SC
Last edited by notyper on 03-06-2012 21:43
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CB77
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(Additional thoughts posted on this subject this morning...from a self-appointed "car expert" in my local market)
"It must be almost spring. Birds are singing, flowers are blooming, temperatures are rising, and gas prices are going through the roof. All are tell-tale signs of summer being just around the corner. In some parts of the country, like Los Angeles, gas prices are averaging $4.36 per gallon, passing the $4 mark much quicker than even last year. Premium fuel there is quickly approaching $5.50 per gallon.
When gas prices escalate, people always start to ask the question, do I REALLY have to put premium fuel in my car? It is a legitimate question, especially when you look in the owner's manual or open your gas flap and it says in large letters, PREMIUM FUEL ONLY, what should you do?
For most people, burning premium gas is not required, but recommended. There is a reason your carmaker recommends premium, and it's not because they are in cahoots with ExxonMobil. The simple facts are that testing determined your car runs at maximum efficiency on premium fuel.
Knowing that premium fuel is how your car runs most efficiently means that you will have the maximum in acceleration and top speeds. It also means your car will get the best fuel economy when running on premium. You can suffer a loss of 10% in fuel economy, or sometimes more, by dropping down to regular unleaded. Even at that, with the spread of gas prices being so large between regular and premium, you will save money running regular fuel.
Be aware that making a switch to regular fuel is not for everyone. I do not recommend it for people with high performance engines, like a Porsche or a Corvette. I do not recommend switching if you are pulling or hauling a heavy load, and I do not recommend it for cars more than 10 years old. Over the last decade, cars' computers have gotten smart enough to adjust themselves to a lower octane fuel and not cause the pinging we used to have to go through. If you go from premium to regular fuel and you do get a ping, I suggest you go back to premium to be on the safe side.
I tend to err on the side of caution when it comes to your car's engine, so I don't recommend using regular fuel if you have a turbocharger or supercharger. Some will say it is fine, but it makes me uncomfortable. If you are not sure what your manufacturer recommends, take a minute and look it up in your manual or look on the government's website, www.fueleconomy.gov . You just can't assume anything with a car, a Smart fortwo micro car calls for premium fuel in their 3-cylinder engine. Go figure.
If you are still on the fence on this subject, I recommend you fill up with a tank of premium fuel and document your starting mileage. Run the tank as near empty as you safely can, then fill up again with regular fuel and see what the fuel economy difference is and how your car performed. If the drop in fuel economy is not substantial, and the car performs well, stay with the regular, you won't hurt a thing.
For most drivers, switching to regular from premium is not going to substantially change your financial situation. A 15,000 mile per year driver averaging 20 miles per gallon will save $31 per month dropping premium fuel at a 50 cent per gallon higher price. That assumes no drop in the overall fuel economy. Most cars will drop a little in fuel economy, so the savings may be actually less.
I have tested cars using both regular and premium fuel and have seen some that showed no drop in fuel economy. Keep in mind that premium fuel has more ethanol than regular fuel does, and it is a fact that ethanol hurts your fuel economy. My conclusion is, if your vehicle does not ping when using regular fuel, use it."
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rsmith
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To me (and this is just my opinion) this entire thread can be summed up with:
penny wise and pound foolish
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white06si
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CB77
As an ASE Master Tech with over 35 years experience in the auto industry, WELL SAID! Yes you can run regular gas in the Si as long as no detonation is heard. Todays computers will adjust and like you said your performance will drop some and your fuel mileage may or may not be effected. Ethanol is corrosive and usually drops fuel economy. If you are hard on you car premium is the way to go, if you use your vehicle to commute and not drive it too hard regular should be fine. The key is detonation which the knock sensor takes care of. My 2 cents worth and by the way I have run both fuels. My mileage is about the same but performance drops. I drive mostly highway without getting into the VTec that often, however I do track this car and of course I use premium. It all depends on your driving style.
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CB77
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white06si,
Thanks for the feedback. Just to clarify, the 2 postings I made on this topic were not written by me, I was just posting comments made by other industry people on this topic. One in the oil biz, and one in the car biz. What they (and you) say seems to make sense to me.
The only concern that I might have has been raised by others on this site, and that is: "Could some damage be done by the detonation that occurs in the engine the split second before the computer "hears" the detonation and retards the timing?"
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RocketRon
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White06si,
As an ASE Master Tech with over 35 years experience in the auto industry, after working on a car, do you say:
"You should be fine"
I am asking because that is what you wrote in post...
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white06si
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Nothing is 100%. We don't live in a perfect world. Just like when you go into surgery, you may have the best Dr. in the world and things can go wrong. There are a lot of people that abuse vehicles and they need to use premium all the time. There are few who can drive a vehicle hard but not abuse them, be in tune with there vehicle, they can use regular and get away with it.
However, it does take sometime for detenation to do damage unless it is excessive and this won't happen if your knock sensor and computer are working correctly. If your knock sensor isn't working correctly you will have a CEL on. If you don't hear detenation you are fine. If you do hear detenation use premium. Several tanks of regular will not hurt even if you hear detenation.
My advise is to use Top Tier fuels http://www.toptiergas.com/retailers.html.
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RocketRon
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The only constant in this thread is that we are in agreement about the reduction in performance caused by using regular.
Then perhaps it makes sense to always use premium on a performance (high revving or turbo) engine because doing so allows an individual to drive his performance vehicule the way it was intended to be driven.
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notyper
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Dude, white06si, just stop.
"Several tanks of regular will not hurt even if you hear detonation"? I can't believe you just wrote that.
When you hear detonation, you're hearing a supersonic, shockwave of an explosion (normal internal combustion engines do not function with explosions, but with rapid burning of the air/fuel mixture) impacting the internal parts of the combustion chamber and piston. Little bits of aluminum are being vaporized off the piston and cylinder head, and several thousand psi of pressure are being exerted on the ring lands of the piston, trying to collapse them. The actual sound you hear is caused by that 75 lbs piece of aluminum we call the engine block _ringing_ from the impact.
More importantly, at full throttle you may not even be able to hear the detonation over the exhaust, road noise, wind noise, etc. So what you don't know can hurt you.
SC
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chavv
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And what happens if engine tuned for regular is filled with premium?
The speed of the flame front is lower on premium, it burns "slower", but how much slower? IS there possibility that 20y old engine (like Honda B16) can be damaged if one is using premium?
AFAIK B16 was rated for european octane 92 and 95, atm premium is rated 100 or even more.
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RocketRon
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Chavv,
I'll awnser your first question:
"And what happens if an engine tuned for regular is filled with premium?"
Premium gas will do nothing to increase the performance of a car that wasn't designed for it, so don't waste your money and save damage to your wallet.
You know, sometimes when you follow a car and it's smell like rotten eggs? That's probably someone using premium on an engine that does not require it. This fowl smell is produced by the unburned fuel thas is being sent to the catalyc converter.
So besides stinking up the place, you're actually putting unecessary stress on your emissions system.
In regards to your second question:
"IS there possibility that 20y old engine (like Honda B16) can be damaged if one is using premium?"
Your not making sense because a B16 engines does require premium.
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notyper
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RocketRon, you are wrong. That rotten egg smell is due to a rich mixture being catalyzed, but running premium fuel in a car designed for regular will not cause the car to run rich.
The difference between premium and regular (91 oct vs. 87 oct) is a slight difference in overall energy content (less than 1%) and more knock resistance.
SC
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Restless
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RocketRon wrote:
"IS there possibility that 20y old engine (like Honda B16) can be damaged if one is using premium?"
Your not making sense because a B16 engines does require premium.
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No, it doesnt require premium.
At least not what is "premium gasoline" in Europe.
ATm the worst gasoline that can be bought is 95 octane, premium is 100 -103
B16 was designed for 95 RON , at least that is what online european catalog say.
PS: In Europe gasoline is RON rated, in USA - MON rated.
For Europe, I'm pretty sure the 160hp version of B16 was sold with 95 RON as recomended. Wiki says 95 RON is approx 87 MON rating. Maybe different tuning for Europe?
:S
This I found in another forum
you should run whatever fuel you need to run, and not much higher based on your motor characteristics and your tune.
if you run too high an octane you will produce less power and leave unburned fuel deposits and crap in the engine.
if you run too low an octane you risk detonation and excessive heat. |
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