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Premium Gas or Mid Grade??

2012Si_kcrow

Well-Known Member
32
11
Houston, TX
Vehicle Model
Civic Si
Body Style
Coupe
What kind of gas is everyone running in their 2012 Si's? The gas cap states "Premium Unleaded Recommended". I feel like I should only run premium but several friends that own or have owned premium gas drinking vehicles (Mercedes, Porsche, BMW...) have told me that they often run a tank of premium then a tank of mid, alternating back and forth due to the price issues. Dad asked me why I would buy a car that only takes premium and suggested I fill it up with regular every now and then...I did this once and my gas mileage went down the crapper! :eek: Seriously, mileage on a tank of regular was around 20mpg. The car did not run any different so to speak, no knocking or valve tapping noises, acceleration still seemed solid and quick:driving:. But, the fact that my mpg was so bad, it made it to where I have not wanted to run anything but premium since. I quickly poured some Octane booster in and topped off with 93 octane after realizing my mpg's were so bad (about 120miles after fillup). So, what are you guys and gals running, 93 octane only? What about in states where 91 octane is the highest you can get (some parts of Arkansas and Missouri only offer 91)?
 

webby

Administrator
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Toys For Tots
52,336
22,453
the car is made to run premium. The car will run on mid or regular, but as you can see, it hurts your gas mileage. The car has knock sensors and retards the timing to prevent early detonation. That reduces power, and hurts your gas mileage. It's not good on the engine to do it, and on say 10 gallons of gas...saves you around $2.00 (.20 a gallon higher for premium usually x 10 gallons = $2.00). You'll achieve better mileage on premium, and you'll be getting the right power out of it as well.

as for states that have lower octane - it's based on elevation.
From Wikipedia:
"In the Rocky Mountain (high elevation) states, 85 AKI (90 RON) is the minimum octane, and 91 AKI (95 RON) is the maximum octane available in fuel[citation needed]. The reason for this is that in higher-elevation areas, a typical naturally-aspirated engine draws in less air mass per cycle because of the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine.
http://en.wikipedia.org/wiki/Octane_rating

run premium
 

2012Si_kcrow

Well-Known Member
32
11
Houston, TX
Vehicle Model
Civic Si
Body Style
Coupe
the car is made to run premium....run premium

lol, thanks webby, that was exactly what i concurred from my experience of not running premium. and your right, the savings is negligible if it hurts your mileage to not run premium.
 

2012Si_kcrow

Well-Known Member
32
11
Houston, TX
Vehicle Model
Civic Si
Body Style
Coupe
So people buy $50-$100K+ cars, then get weird about a few bucks at the pump? :scratches:

lol, i agree with you and what webby said! seems everyone's pinching pennies these days. And that was my first thought when i had heard the same thing for the second time out of someone elses mouth about alternating grades of gas, "I drive a Civic and have no problem putting premium in it, your driving an E class benz and you've got a problem filling up with premium?" Haha, i wonder if he uses that same mentality when changing the oil? I've always ran fully synthetic fluids in all my cars from day I start to change them (Oil, Transmission Fluid, Brake Fluid, Power Steering Fluid, Clutch Fluid, etc). Cost a little more, but I feel I'm doing two things, creating less wear on the car, and being good to the environment:dance:! Of course running cars with no cat (as ive done a few in the past), synthetic fluids, and saying im trying to be good to the environment makes no sense...but you guys get the point! haha
 

BrownCow

Well-Known Member
I haven't taken delivery on my Si yet, so I can't consult the owners manual. What does the manual say is the minimum motor octane number (Mon) and research octane number (Ron)? I ask this because many vehicles say to use "premium unleaded fuel" however that usually means run only the fuel ratings stated in the manual, and only from approved filling stations.

Case in point, my Honda CBR600RR said to run only premium on the gas cap, however the owners manual stated that under normal driving conditions 87 pump octane number (pon) was the recommended fuel. This engine has a 12.2:1 compression ratio and a 15,500 rpm redline.

Remember, Ron + Mon / 2 = Pon and running higher than what is necessary in your vehicle is a waste of money. Like I said, I don't have my Si yet, so I don't know what the owners manual specifically states, it very well could be 91 pon minimum at sea level elevation.

Just some food for thought.
 

webby

Administrator
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Toys For Tots
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from the manual -

2.4 ℓ engine models
Unleaded premium gasoline, pump octane number 91 or higher

Use of a lower octane gasoline can cause occasional metallic knocking noise in the engine and will result in decreased engine performance.
Use of a gasoline with a pump octane less than 87 can lead to engine damage.
 

Anonymous

Well-Known Member
35
17
Denver, CO
Vehicle Model
Civic Si
Body Style
Sedan
The manual says use 91 octane so I use 91 octane.

I agree that you're throwing money down the drain running a higher octane than the manufacturer specifies, and I agree that the computers do a great job compensating for the fact that you're running low octane gas through a high compression engine. But I figure that Honda knows why they're recommending 91 octane and, if they'd meant 89 (or 87, or 85, or...) they would have said so.

For me, it's a maintenance issue more than a money issue and I think running the right gas through the engine is just as important as performing all of the routine/scheduled maintenance that Honda also "recommends."
 

HeelsandEers

Well-Known Member
743
338
Motown, WV
Vehicle Model
Civic Si
Body Style
FA5
I'll never understand people who feel the need to cheap out on premium gas after spending the money on a car that recommends premium. That couple of dollars really worth it?
 

WhiteFG4

Well-Known Member
534
321
Arizona
Vehicle Model
Civic si
Body Style
Coupe
I use premium, and only top tier rated gas stations. My favorite being QT :]
 

Dar-Dar

Mordorator
19,329
9,901
North NJ
Vehicle Model
Civic Si
Body Style
Fiji Blue Pearl Coupe Coolest Member Since: May 15, 2011
I use BP when I cheap out. Sunoco when I'm in a good mood. Lol.
 

KennyGS

How may I help?
11,644
5,513
Keystone State
Top tier fuel sellers - as listed by Honda (and others) > http://www.toptiergas.com/index.html

USA
76 Stations
Aloha Petroleum
Chevron
Conoco
CountryMark
Entec Stations
Exxon
Hawaii Fueling Network (HFN)
Holiday Stationstores, Inc.
Kwik Trip / Kwik Star
MFA Oil Co.
Mileage Stations
Mobil
Ohana Fuels
Phillips 66
Quik Trip
Rebel Oil
Road Ranger
Severson Oil
Shell
Texaco
Tri-Par Oil Co.
U.S. Oil

Canada
Chevron Canada
Esso
Petro-Canada
Shell Canada
 

PistolPete

Well-Known Member
35
26
St Louis
Vehicle Model
Civic SI
Body Style
Coupe
I had this debate with my friend when she bought her used Audi S4. She assured me it could run on less than premium fuel, which is true. Modern engines have knock sensors that can adjust. But why bother buying a performance engine if you want to operate it in limp mode? You aren't running the engine in the efficiency range it was designed for, and it's going to create less power. If a person is concerned about the cost of gas, get an engine designed to run on 87 octane. To me it seems silly to buy a performance car and in all practicality detune it by putting in gas of a lower octane than it was designed for.

Also, as gas increases in price the premium one pays for premium fuel is less as a percentage of the cost of fuel. When gas was a dollar and premium was $1.20 that's a 20% premium. Now that gas is $3.30 and premium is $3.70 it's only a ten percent premium. In that regard it's more of a bargain now.

But, to each their own. I only go to stations that sell 93 octane, they charge the same amount for premium gas as the ones that sell 91 or 92 octane.
 

Adam

Well-Known Member
20
12
the car is made to run premium. The car will run on mid or regular, but as you can see, it hurts your gas mileage. The car has knock sensors and retards the timing to prevent early detonation. That reduces power, and hurts your gas mileage. It's not good on the engine to do it, and on say 10 gallons of gas...saves you around $2.00 (.20 a gallon higher for premium usually x 10 gallons = $2.00). You'll achieve better mileage on premium, and you'll be getting the right power out of it as well.

as for states that have lower octane - it's based on elevation.
From Wikipedia:
"In the Rocky Mountain (high elevation) states, 85 AKI (90 RON) is the minimum octane, and 91 AKI (95 RON) is the maximum octane available in fuel[citation needed]. The reason for this is that in higher-elevation areas, a typical naturally-aspirated engine draws in less air mass per cycle because of the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine.
http://en.wikipedia.org/wiki/Octane_rating

run premium

O.K. so this is only for those that may want to read this - premium fuel users are absolutely passionate about their beliefs and that is O.K. - I also believe the Si does slightly better on premium and evne I use it whenever I expect some sporty driving - BUT my experience is that the car also runs quite comfortably well on regular (89 octane). I have never felt or noticed any power loss nor felt any low rev throttle hesitation or ever heard any metallic pinging. Sure I may only have 190 hp instead of 200 hp; but if I was to take 3 cars and fill one with regular, the other with mid-grade and the last one with premium and asked 10 drivers to drive them on alternate days (not back to back) - I doubt that they will guess correctly which car has what fuel.

I have prepared a very detailed spreadsheet of my fuel usage as I really wanted to measure the differences - but unfortuanelty I can, so far, determine nothing from all this as the results are all over the place. [I think the biggest difference is just how full I top up the tank - not as consistently as I had hoped.]

So my running average on premium so far is 34.6mpg and on regular its 32.7mpg - BUT most of my premium run milage is on long trips in the USA, where premium is so terribly cheap, and my regular fueled milage is mostly on daily commutes to work in the dreaded Toronto traffic. [Yesterday Premium in Toronto was $5.48 per gallon, a full 13% higher than regular. The most that I have paid in the US for premium is $3.69 per gallon and it was only 5.7% more than regular - an absolute bargain!] I might possibly get a 5% milage improvement on running Premium but I am very sure I will not see a 13% improvement to make my premium cost worthwhile.

So this is very much a win - win situation: the magic of these fabulous Honda engines. The Si runs quite well on any grade higher than 87. I am quite sure its better on premium, I have no doubt about this, but its quite acceptable on even regular (in my experience so far). Is there any other car out there that can match the performance AND economy of an Si? If there is some other car that can match this, I have yet to come across it. My total average consumption to date is 32.8mpg.

I have really been trying to measure accelleration pulls in 6th gear on 30 - 50mph and then 50 to 70mph increments with the different fuels; but let me assure you - it is not as easy as I thought (how difficult can it be with a digital speedo?) On public roads it just seems that everyone has to cut in front of me and slow down to spoil a test run! To date my fastest run sequence has surprisingly been on regular gas - BUT I am the first to put it down to experimental error, atmospheric conditions or just me not having stabilized at the start speed or something - its not that easy on public roads - trust me!

Happy motoring!
 
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