Honda Civic Real World MPG

Replying to: wiredpair (Apr 15, 2009 10:32 am)

Replying to: kltron (Apr 10, 2009 4:54 pm)

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Replying to: kltron (Jun 08, 2009 7:36 pm)

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Replying to: targettuning (Jun 09, 2009 4:21 am)

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Replying to: bearcrkrd (Jun 09, 2009 1:06 pm)

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Replying to: targettuning (Jun 10, 2009 7:07 am)

Replying to: targettuning (Jun 10, 2009 7:07 am)

I use a tank of Premium on occasion. Not often. Almost without exception (90% +) the best gas mileage I have ever achieved with a vehicle (2001 Toyota Tacoma Base Reg Cab 4cyl manual 4x2 78,000mi, 2001 Camry Ce 4cyl manual 60,000mi, 2005 Toyota Tacoma Base Access cab 4x2 4cyl auto 39,000mi, 2006 Toyota Sienna CE 36,000mi, and this 2008 Civic LX auto 29,000mi, all purchased new. I am trying to get out of the compulsive buyers club ) has been on a tank of Premium. Especially in the Winter. The Sienna had the 3.3L 6cyl and ran markedly better on Premium at all times. None of the other vehicles, all 4cyl, have been like that. On the 4 bangers I do not notice much of a difference in performance, except the first couple minutes (at most) after cold start and hitting the road. Seem to run stronger. The Regular in Western Washinton is 87 Octane, and it works just fine, too. We are up to $2.75, so that's a good thing! I think I got into this over on the Toyota Forums back when. I tried Honda last purchase. Except for road noise, it has been a match for Toyota.

Stated that the use of "Premium" fuel in a car designed for "Regular" is a waste of money. And the wrong grade of fuel can actually affect mileage in a negative way.
 
Understand that when the spark plug fires and the fuel ignites, it is not actually an explosion. But for sake of illustration I'm using "Explosion" as the term.
 
In a nut shell, and in layman terms, premium has no more energy than regular. Premium simply has extra additives to "SLOW DOWN" the explosion of the fuel that drives the piston down.
 
In engines designed and timed for "Regular" fuel, Premium can be beneficial when the combustion chambers tend to get hotter than normal due to heavy loads, in the mountains, on hot days at high speeds, or when towing heavy loads.
 
Under normal conditions the "Regular" engine is designed to run with the spark plug igniting the gas at a pre determined position of the piston, according to RPM. For instance, at low RPM the plug pretty much fires when the piston is very close to the top of it's travel, so the piston can be driven back down by the "explosion" of the fuel air mixture. At high RPM the spark occurs sooner because it does take a while for the "Explosion" to take place, in the scheme of things. Extremely hot combustion chambers or high compression, or high performance engines, or even deposits in top of the piston that continue to glow from heat can cause the fuel mixture to ignite too soon, resulting in "Pre Ignition". The knocking sound is the piston facing an explosion before it reaches its top of travel. It is being forced down by the pre ignited fuel even though it is traveling upward by momentum. In this case, "Premium" fuel with its additives can slow the explosion, reducing the knock and the sensors don't retard the spark timing as much or at all. So MPG would be better with Premium Fuel under these rare conditions.
 
The knock Sensor "hears" the knock and backs off spark timing, resulting in a later spark and less performance. The piston may be on it's way back down before the ignition takes place. However, under normal driving, the spark timing for "Regular" engines is as perfect as the engineers can make it, when using the quicker igniting 87 octane gas.
 
Using slower burning premium can actually result in lower mileage, when used in "regular" engines. Because the computer is not going to know or have the ability to advance the spark timing, more that normal pre set, to take advantage of the slower igniting Premium fuel.
 
It is a lot more involved than this simple explanation, but this should be understandable to most people.
 
I have found that some brands of gas seem to get better mileage than others and have no explanation for it. I generally fuel up at a "FLASH FOODS" or "QT", to save a few cants per gallon, with good results. Flash Foods say they use Exxon gas. However the tanker trucks simply have Flash Foods on the side of them. I know that "Marathon" supplies a lot of the convenience stores, so it could be that.
 
Lately I've been experimenting with different brands, such as Texaco, BP, Phillips 66, Conoco, Amoco,and Shell. It seems that I get better mileage with the Shell than any other. Besides, it has Oxgenated something that Supposably gets rid of deposits from the cheap gas. So they claim.
 
Kip

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• familydadx4 (Jun 11, 2009 10:20 am)
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Replying to: kipk (Jun 11, 2009 3:54 am)

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Replying to: familydadx4 (Jun 11, 2009 10:20 am)