Last post on Sep 30, 2013 at 1:53 PM
You are in the Honda Civic
What is this discussion about?
Honda Civic, Fuel Efficiency (MPG)
#1994 of 2125 Re: Real MPG Better With Premium?[targettuning]
Jun 10, 2009 (4:25 pm)
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.
#1995 of 2125 Shell oil Brochure I read....
Jun 11, 2009 (3:54 am)
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.
#1996 of 2125 Re: Shell oil Brochure I read.... [kipk]
Jun 11, 2009 (10:20 am)
Appreciate your layman's explanation in comparing premium vs. regular.
You mention better mileage with Shell. Are you talking about 5 mpg, or .5 mpg? Just looking for some type of numerical justification.
I've thought about doing the same type of test. Would appreciate your input.
#1997 of 2125 Re: Shell oil Brochure I read.... [familydadx4]
Jun 11, 2009 (12:15 pm)
Good question. It is an easy demonstration: cents per mile driven. Since we are on Civic MPG, let's take a (my commuter) Civic that gets on R 38 mpg (just filled yesterday in fact) You can use ANY PRICES. But let's demo whether R or P makes sense. (when you come up with the competing R/R prices and your mpg YOU/we can do exactly the same formula)
Let's use (current corner store) prices.
R =$2.81/38 mpg= .074 cents ,
P=$ 3.01/38 mpg= .0792 cents
P is 7% more. On the face of it, no BFD..... However.....
So to get the "same cents per mile" (as regular), one needs 40.7 mpg. or 2.68 miles per gal more. (3.01/.074 cents)
#1998 of 2125 Re: Shell oil Brochure I read.... [kipk]
Jun 11, 2009 (2:51 pm)
"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."
Heavy load doesn't apply to me, but the rest does, and that's when I've got the top mileage on all the vehicles I mentioned. I don't do Premium on all road trips, that's how I noticed the gain, and they do fall most often during warmer Months and include long runs, and hills/mountains.
The little '01 Tacoma showed the least gain in mileage when using Premium. Bet it's still on the road, as I babied it, except for lots of miles driven per year. Problem was if I brought a jacket and thermos the cab was full..
#1999 of 2125 Re: Shell oil Brochure I read.... [familydadx4]
Jun 11, 2009 (5:41 pm)
>"You mention better mileage with Shell. Are you talking about 5 mpg, or .5 mpg? Just looking for some type of numerical justification. "
1-2 mpg increase seems about right with the Shell gas. I'm driving an '03 4WD Pilot.
With the "Flash Foods" gas I was getting 17-19 mpg local driving. With Shell it is more like 19-21. That is a 5%-10% increase. Right now the Shell is about $2.59 and the Flash Foods gas is $2,54. Cost per mile is a bit better with the Shell, and I feel it to be a "better" fuel for the engine and injectors.
REAL WORLD : MORE MONEY CAN BE SAVED WITH THE THROTTLE THAN WITH THE GAS PUMP PRICE.
I didn't see any appreciable difference with the other "Name brands". But,You may find that another brand runs better and gets better mileage in your car. It is a long slow learning process. And I don't have a clue as to why one brand of gas would get better mileage than another. But they sometimes do!
Jun 15, 2009 (11:51 am)
Just purchased 09 civic lx coupe auto. mixed 50/50 driving on first tank calculated with gallons/miles to be 31 mpg. Happy so far.
#2001 of 2125 Re: new Civic [davepod]
Jun 15, 2009 (12:12 pm)
Wish you well.
I have an 08 Civic EX auto with 24,000+ miles that I purchased specifically for the mileage and, quite frankly, it has not performed as I thought it would. I average 29.8 mpg over that 24,000 miles, around what I averaged on an 04 accord EX 4 cyl.
I drive a 80 / 20 hiway/ city mixed route daily. Watch the start stops, travel the speed limit, keep tires inflated, etc, in fact all of the stuff that you are supposed to do.
May look at a hybrid or diesel next.
#2002 of 2125 Re: new Civic [mjsten]
Jun 15, 2009 (8:19 pm)
I'd skip the hybrid assuming your 80hwy/20city won't change anytime soon. Hybrids shine in the city, diesels do GREAT on the highway.
#2003 of 2125 AC's effect on acceleration and mileage
Jun 23, 2009 (12:33 pm)
Has anyone determined the Civic air conditioner's effect on both performance and mileage? Because I can't feel any difference in acceleration whether my 2008 Civic's AC is on or off. I realize that this model of Civic has a somewhat underpowered air conditioner, but it must also be remarkably efficient, as it seems to get the job done without any noticeable drag on the engine.
With my old Corolla I had the habit of temporarily turning the AC off whenever I needed an extra boost of power, for example on uphill freeway on-ramps, but with the Civic I can no longer tell the difference, so I just leave the AC on.
All I can think of is to do some test accelerations from zero to 60 with the AC both on and off to see if there is much difference in the elapsed time or the distance required. (I'll try doing this and then report back.)
I'd also be interested in knowing if anybody with a ScanGauge (or a similar device) has checked the instantaneous mileage in order to determine the AC's effect on highway mileage, while leaving the windows up. All I have found so far is comparisons between AC with windows up, and no AC with windows down, but that comparison is flawed because they are changing two elements at once. I think leaving the windows up and keeping the fan on while switching the AC on and off would be a fairer test.