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Old February 23rd   #1
Minichado
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high MPG and hypermilling?

Quick thoughts on increasing MPG, feedback welcome.

Current status:
2008 Honda Fit 5speed MT
Driving 70 miles a day for work, 5 days a week (down from 102).
Once a month usually a 500 or 700 mile round trip to somewhere on a weekend
very little city driving accept for groceries.
Tire pressure at manufacturer spec (36psi)
some might say I drive like a bat out of hell.. I like to shift near 5grand, is it a sin? I think not.. anyways...

Long recorded MPG average with above information: 34-35mpg on average work week, 35-36mpg on average weekend trip

New status:

Tires at max recommended PSI as per sidewall jargin (44PSI)
trying to NOT red line on my daily commute, accelerating slightly less, keeping more distance between other drivers
Not slowing down in gears anymore.. not a related issue but I'm wanting to be nicer to my transmission.
also, average speed for commute is now 55 or 60 instead of 80 for my previous location.

hoping to push MPG up towards 40 or better with these changes, and the biggest being my driving style I think. I did some reading about 'hypermilling' but the best I can figure is that it means to drive like a paranoid slow person who always drives 5 under and no faster than 45mph... seems impractical

I keep my air filters clean and oil changed every 7-8K and the oil usually comes out barely blackened at that. Never done any carb cleaning stuff in the car per say, though I used to do that to my bike.

Any suggestions? Tips? Criticisms?
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Old February 23rd   #2
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Keeping your tires at 44 psi it going to wear them out faster, which in the long run will cost you way more money then your going to save by a few extra mpg. Honestly I would try and vary what speed I ran on the highway. Maybe try slowing down or speeding up slighly (my vette actually gets better gas milage on hilly streches of highway at 80 vs. 70)
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Old February 23rd   #3
Minichado
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I would agree to the tire wear part, accept I replaced my first set of tires at 30k, and just got a new set of tires last week that only had 20k on them.. going to roll over 50k on the odometer today on the way home, and I've had the car since new with 21 on it when i drove off the lot. All of my other sets of tires were bald beyond belief, even after rotating and checking alignment a number of times.

the wear on the tires was so even (drive tires and rear tires) that I did not attribute it all to my driving habits, though I am assured they contributed slightly.

My car gets best highway milaege at 65 I think.. Made one trip home (360 miles) cruising at 65 the whole way and got 38mpg, but usually I cruise at 70 or 80 and get 36 and get there an hour earlier so it doesn't bother me.

The tire wear is part of what has prompted me to look into this though.
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Old February 23rd   #4
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I've always drive with efficiency in mind, and since you have a manual, you're able to have more control than I do with an automatic.

I don't think you'll run into any more tire wear with higher pressures. I run 50 (max indicated by sidewall spec) on my Accord and find the less rolling resistance helps for mileage.

The other thing I'd look at is shift points and rpm. Obviously you don't want to bog the motor, but I'd try to keep rpms in a minimum range until you get in final gear. On my Accord, I can make it shift (by lifting the accelerator and then depressing it) at under 2500 until I get to the final drive ratio.

Also, keeping momentum is the name of the game. You don't want to hit your brakes or have to accelerate at all. Anticipate the traffic flow and adjust your speed accordingly. I don't come to a full stop very often, and even then just barely. I try to conserve the momentum so I'm not having to accelerate the entire mass on green.

One final thing that helps mileage is power. accordingly_tuned got much better mileage once he added an intake, header and exhaust. He got 38mpg on a trip from here to Dallas in a 1990 Accord Coupe MT. You just have to keep your foot out of it. My Corvette will get 33mpg on the highway if I'm cruising just right. Not so much when I floor it.
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Old February 23rd   #5
Minichado
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Quote:
Originally Posted by Samir View Post
The other thing I'd look at is shift points and rpm. Obviously you don't want to bog the motor, but I'd try to keep rpms in a minimum range until you get in final gear. On my Accord, I can make it shift (by lifting the accelerator and then depressing it) at under 2500 until I get to the final drive ratio.
Yes, basically that. my usual 'bat out of hell' routine is ride the gears from the 3k-5.5k range for shifting.. I've been trying to keep it under 3k while accelling lately, since noone is in my way in the mornings

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Also, keeping momentum is the name of the game. You don't want to hit your brakes or have to accelerate at all. Anticipate the traffic flow and adjust your speed accordingly. I don't come to a full stop very often, and even then just barely. I try to conserve the momentum so I'm not having to accelerate the entire mass on green.
That is why I have been trying to back off of folks. I read somewhere(and then noticed immediately) that when you are close to the car in front of you there is alot of breaking.. and boy do I brake alot! And I also get impatient often, on two lane roads where you can't pass the slow guy. I'm actively making a conscience effort to keep serveral more car lengths in front so I can cruise in 5th and not brake as often. I love rolling up to lights as well, never dropping below 3rd or 2nd.. its those times when it actually doesnt turn green when you want it to and you slam on the brakes that is catches you often ^.^ (but not too often).


Quote:
Originally Posted by Samir View Post
One final thing that helps mileage is power. accordingly_tuned got much better mileage once he added an intake, header and exhaust. He got 38mpg on a trip from here to Dallas in a 1990 Accord Coupe MT. You just have to keep your foot out of it. My Corvette will get 33mpg on the highway if I'm cruising just right. Not so much when I floor it.
I've been doing lots of reading, shopping for struts, looked at supercharger (heh), looked at a header for my fit. Also really interested in tighter suspension but that is not my dept. of expertise in terms of working on cars. On the fence about if I want to put any cash and work into this engine or just keep saving for a second project vehicle, which is my preference (but much more $$)
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Old February 23rd   #6
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Higher air pressure wears your tires out faster? Never heard that. less tire pressure means that you acquire more traction which means that your tires will wear out faster. The main thing is keeping your air pressure equal so that you don't wear certain tires out faster.
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Old February 23rd   #7
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Higher air pressure wears your tires out faster? Never heard that. less tire pressure means that you acquire more traction which means that your tires will wear out faster. The main thing is keeping your air pressure equal so that you don't wear certain tires out faster.
If you put a ton of air presure in the tire it will wear the center faster.........
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Old February 23rd   #8
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Quote:
Originally Posted by EvilZ View Post
If you put a ton of air presure in the tire it will wear the center faster.........
I've heard this as well, but never found it in practice. What will wear out the center faster is locking the brakes on a non-abs car. But that's a different story...
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Old February 23rd   #9
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I'm just talking about filling it to the maximum that it states on the tire. Your right about wearing the centers if you overfill it though

Last edited by A_Cryer; February 23rd at 04:58 PM.
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Old February 23rd   #10
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Quote:
Originally Posted by A_Cryer View Post
The main thing is keeping your air pressure equal so that you don't wear certain tires out faster.
Yeah, very good point. I know in autocross, sometimes tire pressure is varied between tires, but it's not as useful on the street. It's also important to keep them the same because of the load distribution that the tires have to handle.
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I'm just talking about filling it to the maximum that it states on the tire. Your right about wearing the centers if you overfill it though
I wonder if filling it to the max would be considered overfilling? I've seen the inside tread pattern wear out faster on some of my cars, but it's also because the inner pattern didn't have the same depth as the outer grooves.
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Old February 23rd   #11
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I always run mine close to the max and I have never had any problems on anything from a 2 door coupe to a 3500 Dually.
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Old February 23rd   #12
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the number on the side of the tire is recommend if you have the vehicles weigh at it's max load capacity. an overfilled tire (set at max with one passenger) will cause the tire to wear in the center. an under filled tire will wear on the edges, over heat, and possibly blow out. generally you want to stay at the manufactures recommend setting, that is where is suspension of the car is tuned, and where the tires will have the best wet/dry traction. on a radial tire, lowering air pressure for traction can and will make traction worse because you are reducing the tires contact patch. a properly inflated tire will give the best ride, handling, and wear characteristics.
under and over inflated tires also affects brake performance. if you reduce the contact patch, you reduce grip, therefore increasing stopping distance.
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Last edited by Wilson!; February 23rd at 06:33 PM.
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Old February 23rd   #13
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Originally Posted by Wilson! View Post
the number on the side of the tire is recommend if you have the vehicles weigh at it's max load capacity. an overfilled tire (set at max with one passenger) will cause the tire to wear in the center. an under filled tire will wear on the edges, over heat, and possibly blow out. generally you want to stay at the manufactures recommend setting, that is where is suspension of the car is tuned, and where the tires will have the best wet/dry traction. on a radial tire, lowering air pressure for traction can and will make traction worse because you are reducing the tires contact patch. a properly inflated tire will give the best ride, handling, and wear characteristics.
under and over inflated tires also affects brake performance. if you reduce the contact patch, you reduce grip, therefore increasing stopping distance.
Great info. One of the things I've always kept in mind is the contact patch, even when doing wheel upgrades. A larger contact patch is great during dry weather, but it can increase hydroplaning in wet weather because you have less pounds per square inch. That's why a good tread pattern is important for bigger tires, and even then you still have to be careful as they wear out.
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Old February 24th   #14
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When we had a Fit Sport I would run 36psi and drive 60-65mph on longer trips. The best mpg was 42 over a 1800 mile round trip. That car was a hell of a lot of fun, I miss that mpg.
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Old February 24th   #15
Minichado
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When we had a Fit Sport I would run 36psi and drive 60-65mph on longer trips. The best mpg was 42 over a 1800 mile round trip. That car was a hell of a lot of fun, I miss that mpg.
You know, it is a hell of a lot of fun to drive, especially the standard!!! I have owned and totaled 3 cars prior to this, and its my first 'new' car. Best car I have ever owned though.. granted the others were 96 nissan truck, 91 ford exploder (er, explorer) and a 99 oldsmobile

not that I am a bad driver though.. first car was died in a car pileup, the ford literally blew up the engine (and has since been aptly named) and the transmission and engine blew TWICE (EACH!!!) on the oldsmobile before 100k miles...
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Old February 24th   #16
Stephen Freeman
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Simar you are correct about auto cross guys having different pressures. I find 3lbs less in the rear helps rotate the car off throttle. Really helps corner quickly. However before I leave an event I always return the car to 32 PSI all around. (I run much higher depending on the surface)
One thing I have noticed after getting a real air gauge is that tire pressures change very quickly. In two passes It can raise as much as 4 PSI. On the street the pressures change due to usage, asphalt and ambient temperatures. So I am Leary of over inflation. But modern tires seem to handle it. At Bike week last year Dunlop did a free tire pressure check. It was amazing how many idiots were severely under inflated. Gold wing riders loaded down ,crossing the country with 12 PSI in the rear. Thats asking for trouble. Most of the catastrophic failures I see are from under inflation.

Last edited by Stephen Freeman; February 24th at 01:42 PM.
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Old February 24th   #17
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Quote:
Originally Posted by Minichado View Post
You know, it is a hell of a lot of fun to drive, especially the standard!!! I have owned and totaled 3 cars prior to this, and its my first 'new' car. Best car I have ever owned though.. granted the others were 96 nissan truck, 91 ford exploder (er, explorer) and a 99 oldsmobile

not that I am a bad driver though.. first car was died in a car pileup, the ford literally blew up the engine (and has since been aptly named) and the transmission and engine blew TWICE (EACH!!!) on the oldsmobile before 100k miles...
You got that right, the Fit is the MOST fun for the money I'v ever had!!
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Old February 24th   #18
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Most of the catastrophic failures I see are from under inflation.
And this was what the whole Ford-Firestone debacle a few years back was all about.

Ford supposedly told Explorer owners to underinflate the tires to help with rollover stability. Then when the tires blew, they blamed Firestone for quality problems. Firestone blamed Ford for telling customers to underinflate tires. In the end, Firestone stopped being a supplier to Ford. And the Firestone brand and sales was hurt severely.

But little do people know that a lot of Bridgstone technology can be found in Firestone tires. I've run several set of Firestones, including the ones currently on the Accord. And I can tell the Bridgestone technology, especially in the corners.
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Old February 24th   #19
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I believe Ford said to set the tires at 28 psi. At 28 psi the tires were overloaded just from vehicle weight, not including passengers or cargo. An underinflated/overloaded tire cannot shed heat, and disintegrates.
You are supposed to let the tires cool for a minimum of 1hr before checking pressures. If the vehicle is driven one mile, they are considered hot. You can generally guess a hot tire will be about 4 psi more than the tire cold, like Mr. Freeman has observed.
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Old February 24th   #20
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I believe Ford said to set the tires at 28 psi. At 28 psi the tires were overloaded just from vehicle weight, not including passengers or cargo. An underinflated/overloaded tire cannot shed heat, and disintegrates.
You are supposed to let the tires cool for a minimum of 1hr before checking pressures. If the vehicle is driven one mile, they are considered hot. You can generally guess a hot tire will be about 4 psi more than the tire cold, like Mr. Freeman has observed.
So much great info!
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