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    Gas Mileage Thread (come here for answers)

    Ok, I think a lot of people on here have questions about gas mileage and what affects it, what can be done to improve it, etc. So I figured I'd write up a thread on it, just because. I work in an automotive and have been to classes on fuels and gas mileage, so I understand this stuff pretty well.

    First, there are many factors that affect fuel mileage, some are obvious. The setup your running (more HP probably mean more fuel burned, you can't get more power from nowhere), the weight, your style of driving (lead or feather foot), the gas you use.

    Actually, the fuel you use is one very easy to change variable that will almost without fail have a dramatic affect on your mileage. First thing, premium fuel burns more effeciently. I've posted around here several times telling people that I have personal gotten improvements of 4-7 mpg using premium fuel. It will depend how you drive and the brand you use, but premium fuel burns cleaner and more effeciently, leaving you with more power, and therefore the need to use less actual fuel. Pretty cool huh?

    The brand of fuel is important. I know gas prices are a bitch these days, but using the better brands will help you. Not only does it help fuel mileage but it will save you from costly repairs to your fuel system or worse, my current CB came to me with two burned valves because the previous owner used cheap fuel, deposits built up, and burnt the valves. Of course, that won't happen to everyone, but it much more like to happen using cheap fuels (grocery store brands, arco, 7-11 etc (I dunno what ya'll have around the country but those are the cheap brands around here)). Want to know how they get cheap fuel, they buy from refineries what no one else wants, the crap essentially, and mix it together and sell it for cheap. NOT ALL FUELS ARE CREATED EQUAL! I personally use Chevron (with Techron ) and again, I don't know what ya'll have, I would recommend Chevron, Shell or Texaco, none of those are bad.

    Of course, there are other things than just the gas that can affect mileage, but they can be harder to nail down. First, your driving style. We all love to accelerate and that is huge. But I can't and won't try and change that, if you race your car AND bitch about your fuel mileage, stop racing your car or stop bitching. And next time, get a five speed, coasting is the second best thing to ever happen to fuel mileage. In my weekly routine there is about a 2.5 mile stretch of freeway that I can coast down, thats 2.5 miles where I'm idling, great for mileage!

    Now, your car. There are some things you can do to affect mileage, but honestly the ECU does a lot of it. Many things can affect it, heres the abbreviated list: spark plugs, distributor, fuel injector cleanliness (I would recommend cleaning them if you never have), EGR cleanliness, oxygen sensor quality/cleanliness, MAP sensor (not much you can do about that), air filter, the oil you use (yes, synthetic can cause I slight bump up in mileage, less friction I guess, don't honestly know why), weight of the car (for God's sake, keep the car clean! )

    So there it is, the gas mileage thread. My fingers are now tired, and I have to go to work, PM me with questions or post around here. I'd be happy to answer them if I can, I work in a Honda shop and know a fair bit about Honda's, especially for people new to CB's...


    Proud owner of the only JJDM full 2.5" catback exhaust!

    #2
    Nice thread. I've considered using premium too but I've heard it really didn't make a difference but I guess I'll try it out and see what results I get. I live in NYC so I use BP and Shell. I've noticed that sometimes I get 20-22 mpg sometimes using the same driving habits when I use to get 26-27mpg. Bad gas perhaps? Just recently I took a 3 hour drive to MA and i got 32mpg! Idk what it is. I wish i got 32 mpg all the time though.

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      #3
      when i added the iridiums with small gap I went up in power and down slightly in MPG. I would only use premium then both my computers went out. Now with any driving habit or fuel I get a steady 21 MPG. which isnt bad for only having 2nd and 4th gear with a heavy foot and BOO BOO gas. Also I reccomend BP for the gas. itd seems so PURE.

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        #4
        Thats kinda wierd bout the premium, probably just coincidence. And yea, Iridium techincally are supposed to improve gas mileage because they light better, but that's kinda theoretical. I've always had Iridium's so I can't speak to a difference from standards. Have you tried indexing your plugs, they do it on hybrids and I don't know how much of a difference it makes, but supposedly it does.

        BP and Shell aren't bad. We don't have BP in the NW and haven't for about 10 years, they got bought by Texaco (I think) who got bought by Shell..blah blah..Anyways, just avoid the generic crappo brands!

        Ah yes and an update, I filled up yesterday 11.25 gals/270 miles = 23.8 mpg on Premium fuel. Not bad, thats half city half highway!
        Last edited by oranger; 05-10-2007, 12:19 PM. Reason: Update


        Proud owner of the only JJDM full 2.5" catback exhaust!

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          #5
          Mobile Shell Texaco BP . . .

          Well I just gapped to stock spec and made sure not to bend the tips. they are stil under warranty so I may actually return them this weekend. What is plug indexing ?

          Comment


            #6
            i refuse to use BP because after a trip coming back from Columbus Ohio, i stopped to refuel at a BP out in stixs, 3 minutes later after getting back on the freeway the Check Engine Light came on.

            Luckly i had remember watching an episode of 60 minutes about the CEL, a study reported that a high percentage of the time when you have a CEL, it's bad fuel related. Since i just had a tune up done and replaced a bunch of things, reset the time because i fucked up, i knew it couldn't have been anything other than my fuel. i had heard a rumor out in country areas they tend to use a little more ethanol than in the city areas so i decided to just burn it off instead of draining the tank.

            now if there were more Shell stations in my area, i'd use them more often.

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              #7
              Originally posted by 10thcb7
              Mobile Shell Texaco BP . . .

              Well I just gapped to stock spec and made sure not to bend the tips. they are stil under warranty so I may actually return them this weekend. What is plug indexing ?
              First of all, don't gap Iridiums, if you have the correct Iridiums you shouldn't need to and you can only damage them by doing that!

              Indexing the plugs is when you get them aligned to the intake valves, for theoretically better fuel burn.. you know a spark plug looks like (- )with the electrode arm that comes down. The goal of indexing is to get that arm pointed away from intake valves, so that the spark has a direct veiw of the valve. I can't describe very well how to do it, but try googling it, you'll probably find something.


              Proud owner of the only JJDM full 2.5" catback exhaust!

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                #8
                Sounds like the program you watched was a little misleading. While yes, bad gas alone wont cause the light to come on. But bad gas could cause lots of problems that would make the light come on, bad O2 readings, misfires, and other problems. The other thing that is likely, you left the gas cap loose. They have to be turned to 3 clicks or the EVAP system will detect a leak and throw a code. It probably wasn't BP's fault, most likely yours...


                Proud owner of the only JJDM full 2.5" catback exhaust!

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                  #9
                  so will a bad dizzy cause horrible gas mileage? like, 17 in the city?

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                    #10
                    I only get 25 out of my auto wagon everywhere I go. If I grandma it, it will still get 25 and if I put my foot in the throttle body I still get 25...I dont get it.

                    Comment


                      #11
                      Originally posted by StoobyMcDooby
                      so will a bad dizzy cause horrible gas mileage? like, 17 in the city?
                      Well, it could, but it's not the first place I'd look. Anything broken could cause bad mileage. But it's more likely you need to get a little service, use better gas, and lay off the accelerator...


                      Proud owner of the only JJDM full 2.5" catback exhaust!

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                        #12
                        Originally posted by Shag Wagon
                        I only get 25 out of my auto wagon everywhere I go. If I grandma it, it will still get 25 and if I put my foot in the throttle body I still get 25...I dont get it.
                        You're a lucky dude...don't complain! I can't get better than 24 outta mine, its a 5 speed coupe! You're a bastard...


                        Proud owner of the only JJDM full 2.5" catback exhaust!

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                          #13
                          here's a couple of interesting reads:

                          http://www.geocities.com/motorcity/l...0/octane1.html

                          You should use the minimum pump octane (AKI) fuel that will run in your engine without knocking. You're wasting your money on higher octane fuels if there aren't needed to control knock. The two most common myths regarding pump octane (AKI) are that it will increase performance and result in better fuel mileage. You may see improvements in your ride due to the cleaners in higher grade, higher quality fuels, but octane by itself will not have any effect.

                          http://theserviceadvisor.com/octane.htm

                          You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.

                          each excerpt is sited from the corresponding article link. there is a littel more reading in each one if you're interested

                          edit: another one:
                          http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm

                          Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

                          for those of us with stockish f22s and a low compression ratio, the 87 should be fine if not a little better than a higher octane gas
                          Last edited by 90accords; 05-14-2007, 08:30 PM.

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                            #14
                            I've been keeping track since February - you can see outside temp plays a rather significant role.

                            temp Miles # of Gallons MPG
                            10-20* 275 13.02 21.12135177
                            10-20* 246 10.715 22.95846944
                            20-30 314 12.582 24.95628676
                            30-40* 306 12.477 24.52512623
                            60* 309 12.997 23.77471724
                            65* 359 14.29 25.12246326

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                              #15
                              I find outside temps have little effect. My foot has the biggest impact. But I have summer and winter mode, which evens things out.
                              I have a couple projects in mind that should give me a tiny boost and even things out more. Regulated intake temperature and the valve to switch from small intake to large. I'm curious how it'll affect low end torque and whatnot, too.

                              OT: Once I get my IABs setup, I wonder how many ricers will ask if I have the mad vtak when the intake valve and IABs open. it'll be nifty though. All the noise and none of the VTEC.
                              Opal Metallic Green '92 LX 2dr manual, 181k miles, '94 prelude VTEC wheels for summer (steelies with snow tires for winter), Omni-power struts/springs, and other junk

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