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Sedans Honda Civic Honda Civic Real World MPG
2058 messages, Last post on Aug 26, 2009 at 6:19 PM
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the increased power in higher octane fuels comes from the "slower burn" of the high octane fuel. This sounds opposite of common sense, but a slower/ more even burn will give more power than a quick flash burn of a low octane. Higher compression engines are more prone to compression-ignition, that is, the fuel burns due to pressure instead of spark, and since compression burn (similar to a diesel) almost always happens too soon, pinging is the result. The engine with knock sensors will detect this and retard or delay the spark to reduce the pinging. Unfortunately retarding the ignition also reduces the power. So by using low octane fuel that is prone to pinging, the engine with knock sensors retards and power is lost. That's how lower octane fuel lowers power. In engines without knock sensors, the burn is just faster and that faster burn reduces power. And the knocking severely impacts engine life. The loss of power is noticeable in some cars more than others. My 97 Camry v6 (3.0L, 10.5:1 compression) was very much affected by octane. 93 would make it scream. My wife's 02 Highlander (same engine but with VVTI) has much less noticeable power loss on 87 vs 93. The VVTI in Toyota's case combined with newer ECU controls seems to avoid much of the discernable power lost by using 87 (91 is recommended in both the 02 Highlander and the 97 Camry). Honda's controls work in basically the same way. |
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Replying to: wai (Sep 16, 2008 5:59 am) |
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Replying to: targettuning (Sep 16, 2008 6:47 am) Well stated and I agree !. Most of the research I did came from publications produced by various oil companies. Slower burn of high octane allows the ignition timing to be set earlier. This will not necessarily benefit an engine that has a "timing" designed for 87 octane. Except when the combustion chamber is being really stressed above and beyond normal, and running hotter than normal. In other words, using 93 won't necessarily trigger the timing to advance, so the slower burn can be utilized. That is my understanding and we normally get excellent mileage. I personally can't understand why folks buy an "Economy" car and want to find ways to spend as much money as possible on fuel. To each his own !  Kip |
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Replying to: targettuning (Sep 16, 2008 6:47 am) I've never seen gasoline lower than 87 octane, at least not labelled as gasoline.
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Replying to: izmirian (Sep 15, 2008 5:29 pm) Well I get that in my 2008 Civic Si which is a 6 spd manual and 197HP. I think your mileage will go up as you get more miles on the car. |
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Replying to: kenlw (Sep 18, 2008 9:58 am) |
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Suddenly, without any apparent reason, my MPG jumped dramatically from 26 mpg to 37 mpg. It's an 07 Civic EX, automatic, with 30,000 miles on it. I had been getting a low of 25 mpg to a high of 27-point-something for the life of the car, but then two tanks ago, it went up a little... to 29 mpg on one tank. Then, two days ago, I drove from So Cal to Fresno, about a 500 mile round trip. I got 37.5 mpg. I had the air conditioner going full blast, and my gas was the same... Costco 87 octane. Not only that, but I had to scale Angeles National Forest through I-5's Grapevine. This meant climbing with high RPM's for miles. I can't understand it. Since the beginning of this model year, there seems to have been two camps of owners. Those who get Civic-like mpg, and those like me who did not and who were surprised by lower mpg. Now my car has dramatically joined the first group. Has anybody else had an experience like this? Is there any rational explanation for it?
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Replying to: thechair (Sep 20, 2008 6:30 am) HOWEVER...to jump *that much* (27 to 37) is really incredible if you haven't changed your driving type or habits. Note, however, that if you usually do all stop-and-go city or sit in traffic, and then your 500 mile trip was highway, one could expect a change like this. It would be interesting to see what your next few tanks are like while you do more of your "normal" driving--please keep us posted. And from Honda: The Insight comes back as a 4-seater in the spring. I haven't heard mpg estimates on that yet, though (not that I have any complaints with 40+ mpg in the Civic this summer). ...kl... |
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No one gets the same gas mileage and no one should get all worked up when others seem to get a better mileage from the same car. We all drive differently I drive one mile one way in the morning without the engine warmed up, hit a couple of long red lights and get about 15 1/2 miles per gallen. ( 08 Accord by the way. Had a 07 Civic with 22 City/34 Highway mileage with below driving habits ) I drive with the car warmed up, and further, and sometimes with shorter red lights and longer stretches of city road and get 22 miles per gallen. I had 32 lbs of air in the tire and got less miles per gallon then later tried it with 37 lbs of air and got better gas mileage. Later still, when the car was broken in the gas mileage increased. So, unless we know exactly how someone drives, where they drive, in what weather, amount of air in tires, air on or off, and so on, we can never go by someone elses mileage. |
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Just and update, have not posted for awhile. Our 2007 1.8 EX Coupe on a recent trip from Mobile, Al to Chicago, Il. delivered 40.5 MPG on the road. Seems like mileage has gotten better. With AC on, 2 people, luggage. I do top off the tank, to the rim, car has not blown up as yet (some have warned about topping off). The reason I top off is really check the mileage as accurately as possible. Around town, stop and go getting 25.5 to 28.5. My goal was to purchase a 40 MPG car (on the road mileage) and the Civic has delivered. 73 MPH I can live with, really a pretty comfortable speed.
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