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Discussion Starter · #1 ·
I've spent the last hour reading threads on gas mileage. Everything was old and pretty basic stuff, so I started a thread for more advanced tips.

BACKGROUND: I just bought a 2008 Odyssey Touring with 158,000 miles. It does not have the run flat tires or the vcmuzzler. I went on a mostly interstate trip at 76-77mph with the AC on and averaged 21.5mpg for the 350 mile trip. Immediately prior to the trip, I changed the oil with Mobil 1 Synthetic 5W-30 and put in a new air filter. I run 40psi tires all around.

QUESTION: What mechanical suggestions do you have to improve gas mileage. Please, let's avoid rookie stuff in this thread (e.g, drive slower, avoid fast starts). I'm thinking of 1) changing transmission fluid 2) doing a Seafoam engine treatment 3) changing the O2 sensors 4) pumping the tires up to 42psi 5) changing the spark plugs 6) removing the rear seats to reduce weight (not much advantage here, but I don't want the seats in the car so why not?) 7) adding an aftermarket power chip. Any other suggestions?
 

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You need to take a look at fuel trims with a scan tool. I found that my van, while running OK, was adding about 10-20% more fuel...not enough to set a code but enough to affect gas mileage. Replacing all four O2 sensors fixed it. The OEM sensors are made by NTK and can be purchased at RockAuto.com for much less than the dealer and they're an exact match.
 
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Discussion Starter · #3 ·
Thanks. I was thinking of installing an OBD2 Scan tool and using it to fine tune my driving style. I'll check out the O2 sensors.
 

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Please, let's avoid rookie stuff in this thread (e.g, drive slower, avoid fast starts).
drive slower :D

and 7) adding an aftermarket power chip...

are you serious? and you have the impudence to call physics 'rookie stuff'?




as for increased tire pressure, I've owned and my dad still owns a TDI diesel, so I've been pretty active on the forums there; let me tell you those guys are pretty hardcore about fuel economy. anyways, there has been a few that ran high tire pressures, let's just say they don't anymore. unless you like saving a couple of pennies and replacing sets of shredded $500 tires.
 

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Buy yourself an Ultra-gauge or a Scan-gauge or similar for real time info and lots of it. O2 sensor readings,instant MPG, and a LOT more.
Use the recommended spark plugs.
Use the proper wt oil and use synthetic, like Mobile 1.
Your oil recommended wt is 5w20 but I would imagine that a 0w20 full synthetic oil like Mobil 1 would be just fine. Your choice.
Your owner's manual calls for Honda Z-1 atf. If it hasn't already been changed in the last 30k miles or so, I sure would recommend doing at least one drain and fill with the Honda DW-1 or another good synthetic atc, such as Valvoline MaxLife Dex/Merc atf (around $18 for a 1 gal jug).
Check your PCV valve.
Air filter?
Power Chip???? You're kidding, I hope.
On my '03, driving at 60 mph gives me around 5 mpg more than driving at 75 mph. Wind resistance on an Ody is a LOT.
Buffalo4
 

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Discussion Starter · #6 · (Edited)
Thanks for the suggestions. FWIW, I just provided my recent trip MPG to give posters an idea of the vehicle's current MPG. My 2nd tank of gas averaged 21.8 MPG with some combined rural and interstate driving (70-75). There doesn't appear to be a power chip for this vehicle, but I thought it was worth asking. I'm changing the trans fluid this week and it has a new air filter. Thanks for the suggestion to check the PCV valve. Where I drive, it's dangerous to go 60 mph on the interstate during rush hour. I've purchased an OBD2 scanner and hope to get instantaneous MPG to see if the change between speed and mpg is linear or whether it ramps up at a particular speed. I'm also curious to see how (or if) MPG changes when the ECO mode comes on.
 

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Discussion Starter · #7 ·
Update. I received the OBD2 scanner to show instantaneous MPG. It was enlightening. Although I need to use it longer to get more feedback, it appears a major culprit with this vehicle is acceleration. Accelerating from a stop resulted in a drop to 5 mpg! I'm not talking about a jackrabbit start or even keeping up with traffic from a stop light. Anything faster than grandma driving to church resulted in a drop below 8 mpg.

To put this in perspective, my Dodge QuadCab Ram 3500 diesel weighed nearly 6,000 pounds and didn't drop below 10 mpg on acceleration.

Even at cruising speed, a slight acceleration dropped mpg to 10. On the other hand, fuel economy didn't seem to vary much whether I was driving 50mph or 65 mph. (I need to confirm that with a longer drive at each speed.) I haven't checked instant mpg at higher speeds yet, but I suspect it will drop logarithmically with speed.

If I notice anything else interesting, I'll report back.
 

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Use your scanner to take a look at short term and long term fuel trims at idle, and at 2500 RPM. You will have a long term (LT) and a short term (ST) for both banks. Post those numbers.
 
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WillowTheDog,

One of the main reasons that the mpg at first takeoff is so high is that it is in 1st gear.
When you are going around 60 mph, downshift one gear and see how much the mpg changes.
Being able to stay in that 5th gear makes a lot of difference. So, low gears equal low mpg, overall.
And, yes, jackrabbit starts even use more fuel, but for a very short period of time.
Buffalo4
PS: For the best mpg, always drive downwind!! :ahh: :cheers:
 

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That's a ridiculous way to look at gas mileage. My Dakota had the instant MPG readout, and I normally got about 15 MPGs around town. But stopped at a red light at idle, it was 0 MPGs. Is that enlightening at all? Not really. On a side note, what's the lowest MPG readout you've seen on the diesel truck?

I'm not sure how that instant MPG thing even works, I mean there isn't any sort of flow rate sensor on the fuel rail and return lines, so how would it know? Best I can figure is it takes some kind of assumed flow rate for injector size and pulse width and does a calculation from there. In any case, I wouldn't make any bets based on that reading.

If anything, the best way to hypermile is to get a vacuum gauge and just use smooth pedal input (based on the vacuum gauge readings) and coast a lot. Since you already got the OBD thingy, just use the map sensor readings.
 

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Use your scanner to take a look at short term and long term fuel trims at idle, and at 2500 RPM. You will have a long term (LT) and a short term (ST) for both banks. Post those numbers.
Gas mileage is a direct result of the numbers shown in the fuel trims. You don't need to run a full tank of gas to find a problem. As I mentioned above, look at the fuel trims at idle and 2500RPM, and during a drive, and you'll have your answer. Based on the fuel trims you can actually start looking for the cause of the reduced fuel economy.
 
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Here are my thoughts:
1. Total gasoline cost for 99% of non truck driver population is 60-90% city driving miles. My 2001 ody - gets 15 city if driven "Socker Mom" style and 18.5 mpg if driven conservatively (under 2,100 acceleration RPM's) - not hypermiling.

2. Driving an electric EV - Leaf you can see the impact of highway driving instantaneously when the wind hits you from a front quadrant - 15-25% change, moving the wheel left or right from a straight line 5-10% change.

3. Speeds of 50-55, 55-65, and 65-75, and above 75 (much higher chance of death if there is a crash) affect MPG. Small things to reduce wind resistance are remove the cross members of the rook rack, or take it down completely - its quieter. I lowered the van 1.2" with aftermarket shocks and springs. Reduces under car wind resistance = ? and hwy wind buffeting with large trucks is highly reduced.

4. Friction - I use Continental low rolling resistance tires - the best I have every had on any car, have been Michelin, Goodyear, Yokahama, don't hold a candle to Continental IMHO. Make sure the car is aligned to better than 50% tolarance limits. Added rear camber adjust bars to lessen the wear of camber while tires are on the back. This also lessens the friction the car has in the back and increase tire longevity.

What is it all worth to talk about this?
190K miles 62% city mpg of 17 and 38% highway mpg of 26 at life time Chicago gasoline average of $3.65 comes to $35,428
Compare that to same miles and mix of 15 city and 21.5 hwy comes $40,922 - $5,494 delta or 15.5% increase in gas cost lifetime.

When I drive the car I get 18.5 city and 26 hwy since I am the main hwy driver - this comes to $33,377 - that makes a delta of 7,545 or 22% increase.
 

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Isn't 21-23 mpg about average for our vans? I get a fairly typical 22mpg.
 

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Isn't 21-23 mpg about average for our vans? I get a fairly typical 22mpg.
Source: https://www.fueleconomy.gov/feg/bymodel/2018_Honda_Odyssey.shtml
Note: Change the last two year digits your desire in the above URL

Fifth Gen 2018 - City 6sp 19 - Hwy 28 – 10sp trans on top trims – 280HP - J35Y6
Fourth Gen 2017 - City 6sp 19 - Hwy 27
Fourth Gen 2016 - City 6sp 19 - Hwy 27
Fourth Gen 2015 - City 6sp 19 - Hwy 27
Fourth Gen 2014 – City 6sp 19 - Hwy 27 All 6sp trans al trim levels
Fourth Gen 2013 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2012 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2011 - City 6sp 19 5sp 18 - Hwy 27 – 248HP - J35ZA
Third Gen 2010 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2009 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2008 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2007 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 24
Third Gen 2006 - City 6sp 17 5sp 17 - Hwy 5sp 23 6sp 26
Third Gen - 2005 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 26 – 255HP J35A6 /J35A7-VCM EX-L/Trng
Second Gen - 2004 - City 5sp 16 - Hwy 23
Second Gen - 2003 - City 5sp 16 - Hwy 23
Second Gen - 2002 - City 5sp 16 - Hwy 23 - 240HP 3.6L v6 – J35A4
Second Gen - 2001 - City 5sp 16 - Hwy 23 – 210HP 3.6L v6 – J35A1

AJB - you said 2013 TE - is that a Touring Edition? If so then EPA has you at 18/27 - if you get Hwy of 22 then I am guessing you are doing 75-80 mph

- I hope you do not drive your family at that speed, if crashed you would all likely not survive a serious accident at that speed.

My philosophy is that I can kill myself if I choose but to will (force) that upon others is not acceptable.

If you get average 22 mpg then that is a much safer ball game and your family and friends should be thankful!!
 

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Thanks looks like I'm right int eh middle of city/highway.
 

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I cannot answer your question directly, and I don't know what Honda's recommended tire pressures are for your car, but running the tires over-inflated, if that is what you are doing or propose to do, is not the best idea. You may save on fuel, but you are likely to wear out the centre tread of your tires more quickly. Tire pressure settings are determined by wheel loadings and by handling/roadholding considerations and are recommended for cold tires. My daughter in Australia runs an older Odyssey than yours; her local garage recommends running about 5psi above Honda's recommendation and reckons this is normal practice in Australia. Initially, as a former Michelin R&D engineer in UK/France, I was puzzled by this, until I realised that the garage man's recommendation was based on the assumption that everyone checks/adjusts their tire pressures at the gas station after driving there, rather than at home before a trip. In this situation the tires are no longer cold (i.e., at ambient temperature) but have been heated by the trip to the gas station. In this situation it is fine to overinflate above the cold recommendation by 3 to 5 psi, depending upon ambient temperature, the higher the ambient the higher the over-inflation [in Queensland, Australia, ambient temperatures in the summer are around mid 30s Celsius (mid 90s Fahrenheit) and warrant the higher inflation pressure for hot tires - even in winter, daytime temperatures are rarely below 70 Fahrenheit]. Returning to fuel consumption, I don't think your ability to measure fuel consumption will be sufficiently accurate to determine any differences due to the changes you list above, except perhaps with the aftermarket power chip (although I don't know what a Seafoam engine treatment is - flushing oil perhaps?). And again, personally I would hesitate to deviate from Honda's recommended lubricants.
 

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Also note that just looking at a single tank fill can be very mis-leading, too many factors come into play.
Better to log every addition of gas, then average out.
For example, (2005 EXL) my last fill showed 23.7 mpg, but averaging that into the last 5 fills, I get 22.9 mpg and then going further, the last 9 fills yields 20.6 mpg.
When you do this over the long haul, you'll see a trend just by season (summer-winter) and use (city/local/short - hwy-long)
19-24 is common for me (local/Chicago/winter - hwy/+200mi/summer)
 

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I now have an '11, so I don't have the same generation any longer. Previously I had an '06.

For me, on freeway drives or longer trips, I do a few minor things to keep my gas mileage in control. I run my tires just about 2-3 psi above the recommended 33. My tires wear more on the inner and outer shoulders so I can justify trying to keep an even wear and getting better gas mileage. I also use the a/c more than the putting the windows down. On my last drive, I noticed a significant drop when using my sunroof/air flow to control temperatures (It was cool that morning so we didn't have the a/c on). I also use my cruise control extensively. I can get 27-28 mpg with a full vehicle on long straights if I keep it at 65. As I approach 70, it goes down little by little. I have a few places where the speed limit is 70 so I'll go up to 70 (but not over) if I'm trying to conserve but I notice a significant drop for each mph above 69. Even if I have a steady foot on the accelerator at 65-68, my foot doesn't do as well as the cruise control.

All that said, I frequently put my windows down around town, and if I use very steady and conservative acceleration and deceleration at lights, I'm usually getting around 19-20.5. I remember that my 2006 was harder on gas mileage than my 2011.
 

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Source: https://www.fueleconomy.gov/feg/bymodel/2018_Honda_Odyssey.shtml
Note: Change the last two year digits your desire in the above URL

Fifth Gen 2018 - City 6sp 19 - Hwy 28 – 10sp trans on top trims – 280HP - J35Y6
Fourth Gen 2017 - City 6sp 19 - Hwy 27
Fourth Gen 2016 - City 6sp 19 - Hwy 27
Fourth Gen 2015 - City 6sp 19 - Hwy 27
Fourth Gen 2014 – City 6sp 19 - Hwy 27 All 6sp trans al trim levels
Fourth Gen 2013 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2012 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2011 - City 6sp 19 5sp 18 - Hwy 27 – 248HP - J35ZA
Third Gen 2010 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2009 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2008 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 25
Third Gen 2007 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 24
Third Gen 2006 - City 6sp 17 5sp 17 - Hwy 5sp 23 6sp 26
Third Gen - 2005 - City 6sp 17 5sp 16 - Hwy 5sp 23 6sp 26 – 255HP J35A6 /J35A7-VCM EX-L/Trng
Second Gen - 2004 - City 5sp 16 - Hwy 23
Second Gen - 2003 - City 5sp 16 - Hwy 23
Second Gen - 2002 - City 5sp 16 - Hwy 23 - 240HP 3.6L v6 – J35A4
Second Gen - 2001 - City 5sp 16 - Hwy 23 – 210HP 3.6L v6 – J35A1

AJB - you said 2013 TE - is that a Touring Edition? If so then EPA has you at 18/27 - if you get Hwy of 22 then I am guessing you are doing 75-80 mph

- I hope you do not drive your family at that speed, if crashed you would all likely not survive a serious accident at that speed.

My philosophy is that I can kill myself if I choose but to will (force) that upon others is not acceptable.

If you get average 22 mpg then that is a much safer ball game and your family and friends should be thankful!!
Where did you get these numbers? I don't recall the Gen 3 Odys ever having a 6 spd transmission.
 

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John Clark - you are correct - the third gen chart should be with and without VCM - Variable Cylinder Management - only 5 speed transmissions - Thanks for the correction:

Fifth Gen 2018 - City 6sp 19 - Hwy 28 – 10sp trans on top trims – 280HP - J35Y6
Fourth Gen 2017 - City 6sp 19 - Hwy 27
Fourth Gen 2016 - City 6sp 19 - Hwy 27
Fourth Gen 2015 - City 6sp 19 - Hwy 27
Fourth Gen 2014 – City 6sp 19 - Hwy 27 All 6sp trans al trim levels
Fourth Gen 2013 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2012 - City 6sp 19 5sp 18 - Hwy 27
Fourth Gen 2011 - City 6sp 19 5sp 18 - Hwy 27 – 248HP - J35ZA
Third Gen 2010 - City VCM/17 NonVCM/16 - Hwy VCM23 NVCM25
Third Gen 2009 - City VCM/17 NVCM/16 - Hwy VCM23 NVCM25
Third Gen 2008 - City VCM/17 NVCM/16 - Hwy VCM23 NVCM25
Third Gen 2007 - City VCM/17 NVCM/16 - Hwy VCM23 NVCM24
Third Gen 2006 - City VCM/17 NVCM/16 - Hwy VCM23 NVCM26
Third Gen 2005 - City VCM/17 NVCM/16 - Hwy VCM23 NVCM26 – 255HP J35A6 /J35A7-VCM EX-L/Trng
Second Gen - 2004 - City 5sp 16 - Hwy 23
Second Gen - 2003 - City 5sp 16 - Hwy 23
Second Gen - 2002 - City 5sp 16 - Hwy 23 - 240HP 3.5L v6 – J35A4
Second Gen - 2001 - City 5sp 16 - Hwy 23 – 210HP 3.5L v6 – J35A1
 
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