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Improve my gas mileage

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Old 07-20-2003, 01:42 PM   #1
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My S is my daily driver. My commute is about 40 miles each way, mixed surface streets and freeway. Depending on my mood I will sometimes drive casually and sometimes aggressively, and generally vtec at least once a trip.

I calculate my mileage almost every fill-up. It usually averages out around 23 mpg. This has been for casual interest, and I've never cared much to improve it, but when I heard people on this forum talk about getting 30 mpg or better it made me wonder how they do it. Out of curiosity, on my most recent tank I decided to see just how much better I could do. It turns out not very much.

So maybe you guys can give me pointers. I figured the most important thing would be to keep the rpms low and accelerate very gently. I began shifting below 3500 rpm, and cruising as close to 2500 as I could get. I never really pressed on the accelerator, just caressed it as I entered each gear and let the engine take its own time getting up to the next shift point. All this had the effect of making it feel like driving a semi: accelerate gradually for a couple of seconds and shift, accelerate and shift, okay I'm across the intersection now in third gear. Accelerate and shift, accelerate and shift, accelerate and shift, and I'm in sixth going about 45. This has all taken about 30 seconds and the car behind is tailgating. Don't even think about vtec. Approaching every corner and red light, put it in neutral and coast.

That felt like the longest week of my life. Driving lost all its excitement. The car was just transportation, no different than my old VW Rabbit. And guess what? When I finally was able to fill the tank, at 270 miles, it took 10.5 gallons, for a measly total of 25.75 mpg. Okay, it was better but not the dramatic improvement I hoped for. What a disappointment. But now that I've done it, I won't ever again feel bad about not trying for better mileage, since I can't make it that much better anyway. I'm driving for the fun of it again and loving life.

So what did I do wrong, aside from thinking it mattered in the first place?
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Old 07-20-2003, 02:52 PM   #2
 
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I did the same, bro. I even took off my spare tire(keep the tools, though) and fill up only half a tank!!! I still got 26-28 MPG at best, all medium trafic city VS. 21-22MPG with spare tire and full tank of gas.

My answer is "HALF TANK ONLY PLEASE!!"

Maybe those 30MPG and up are the mileage from highway?
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Old 07-20-2003, 03:30 PM   #3
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I keep extensive records of my milage, and I can tell you from my experience that at 25 to 27 mpg in mixed driving you are probably doing as well as you can. I have only been able to top 27 once and that was exclusively freeway miles.

In general I get about 21.5 mpg in mostly rush hours but mixed driving. Just enjoy the car. The difference in the mpg is not significant. You bought it to enjoy it.

I keep track because I like to know.
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Old 07-20-2003, 03:58 PM   #4
 
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Get a vafc and it will lean out your factory set air fuel mixture, which is set at a very rich mixture. Of course it will cost you lots of money to buy the vafc and tune it, which makes my suggestion pointless because you will probably vtec even more negating all of the gains in gas mileage, making this post irrelevant except for me to post more pointless and wise ass suggestions.
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Old 07-20-2003, 04:01 PM   #5
 
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I think you have to report either city mileage or highway mileage. Doing a combination mileage is somewhat pointless because every individual will have a different combination of city/highway.
I'm guessing that those high numbers you have seen are from those who have taken a highway trip from one city to another.
For example, when I reported getting 39.9 miles per Canadian gallon, this was fueling up at the edge of the city, and immediately going out and driving on the highway till I fueled up again. Speeds rarely went below 55 mph. And this is with normal shifting up through the gears and some passing.
In the city only, I was getting about 26 (Cdn gallon).
The trouble with your calculation is that even though you do a 40 mile X 2 commute, you have all that stuff before, in between and after, where you are shutting off the car, going through traffic with lights, stop signs, parking lots, idling, etc. All these things can kinda screw up your car's apparent mileage when you compare to others who report mpg.
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Old 07-20-2003, 04:28 PM   #6
 
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If we can VTEC and still get 23 mpg, why would you even want to get more boring miles to the gallon!!!
Just my smart-ass remark!
-M
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Old 07-20-2003, 06:33 PM   #7
 
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Hey, I'm really sorry that I get 29+ mpg average for 14 months and 12,000+ miles. I'm just unfortunate that I don't have a freeway nearby, where I can blast along at 75 or more. Of course, I don't have many stop lights around town either (I actually tend to avoid them by going a bit out of my way.) I think my mileage is pretty good because the major part of my commute is between 45 and 60 mph. I once read that the best mileage is attained at 30 mph (that was about 35 years ago in drivers' ed), but I feel that the old double nickle is a pretty economical speed also. I had two previous vehicles that had an instaneous mileage read out, and I guess I just got used to doing things to keep the number high. Maybe being at 4500' altitude also gives me less wind resistance I definitely don't practice driving like you've used as your example. Maybe my car is just a jewel!
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Old 07-20-2003, 07:10 PM   #8
 
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when I was poor and my CRX was my daily driver, I became fanatical about trying to eek out as much mileage from my car. call it a poor boy's hobby.

my overall average is 38.47 MPG in a '89 Honda CRX, with 172000+ miles that I've had since April of '00, bought with 137387 miles on the odo. I almost always filled up when the tank was near empty, kept the receipt, and was fanatical about putting everything into an Excel spreadsheet. by filling up when the tank was near empty each time, this allowed me to more easily divide the # of miles driven by the # of gallons I had to put in, and it didn't make the graphs all screwy. (although apparently, having a nearly empty tank means your pump is more likely to siphon up the gunk at the bottom of the tank, and your fuel filter will have to work harder. so if you're going to do this, pick a line on your digital fuel gauge, and fill up EVERY time it reaches that line)

the more money I started to make, the less concerned I was about fuel economy, so my average MPG used to be higher. and since it's next to impossible to figure out Hwy -vs- City miles, I'll just say that they were about 50/50. I can't really know for sure though. I kept pretty good notes tho on my spreadsheet whenever I took a long highway trip.

I even did an experiment using 89 octane for some time, and saw ZERO benefit. it only cost me more $.

I filled up almost exclusively with Chevron gasoline, 87 octane.

here's how I did it:
1) when I anticipated that I would be having to come to a stop, or even to slow down, I put it in neutral and coasted. sometimes for a long time.

2) downhills, I often coasted. THIS IS VERY BAD-- if your brake fluid heats up and starts to boil, your brakes can fail. (Thx Car Talk guys on NPR for this bit of wisdom! ) I did not know better. now, I put it in 4th and take my foot off the gas. I don't know if this uses more fuel than just coasting (my suspicion is it does) but it is a heck of a lot safer.

3) accelerate slowly. no, even more slowly than that.

4) draft behind big semi trucks. (NOT recommended, else your S will be rock chip'd repeatedly) on top of that, some of them get kinda freaked when they know there's a car right on their rear, and they can't see it because you're so close. how close? close. I just kept in mind that I could brake faster than the semi so I just kept enough room to have enough time to brake. when I used to have a car with a sunroof (not my CRX), by putting your hand out the top, you can feel the wind resistance change. then you know you're really drafting. in an S, very easy to do also. but remember: rock chips.

5) get into as high a gear as possible in the shortest amount of time without bogging your engine down.

I stopped keeping track of my mileage in January when I realized I just didn't care anymore. if anyone is interested, I'd be happy to put a copy in a Yahoo briefcase for anyone to download. it's pretty rough-- just notes and graphs for my own benefit, but if you're curious I'll be happy to share it. just let me know.
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Old 07-21-2003, 06:45 AM   #9
 
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I normally get around 21 or 22 mpg with city and hwy driving. Did the same thing about driving like my grandmother and only got around 25 after that. Then took the car on a road trip to GA/FL and got on average 29 to 30 mpg.
Think I'm going to take my spare out too and see what happens.
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Old 07-21-2003, 09:13 AM   #10
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I got a little over 31 mpg once, interstate driving @ 65 MPH, cruise on, top up, a/c off (it was chilly).

Ordinarily I get in the low 20's with A/C and a little VTEC'ing here and there. I was getting 24 or 25 mpg before summer rolled around and I didn't have to run the A/C all of the time.
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