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What MPG are you getting with VCM Turned Off?

11K views 39 replies 19 participants last post by  dr bob  
#1 ·
I have had VCM Muzzler installed for the past 3 years on my 2012 Pilot Touring 4WD and usually end up getting around 12-14 mpg combined between highway and city driving in Los Angeles.

What MPG range is everyone else on here getting with VCM disabled?

It feels like my MPG is low for what I probably should be getting and am trying to go about figuring out how to improve.

Additional Info on my Pilot:

  • It has a 2" spacer lift on it
  • 2 small oil leaks from the rear main seal and oil pan, which result in 1 drop on the driveway per month, so not a big leak.
  • Spark plugs were replaced <2 year ago (Denso Iridiums) and just inspected and cleaned last weekend. No oil fouling or oil in tubes or coils.
  • PCV valve was replaced when VCM Muzzler installed.
  • Have not replaced EGR yet but have a new one on hand. There are no indications that it's bad.
  • Had a check engine light come on last weekend (P0420) which I think was due to a pretty big tear that had developed in the air intake boot, which I promptly replaced, and seemed to fix the issue.
  • The engine runs and sounds fine with no knocking or rattling.
  • Air filter is new.
  • Here are pics of my pilot: https://instagram.com/familykuruma?igshid=YmMyMTA2M2Y=

Thank you in advance for sharing the MPG you all are seeing with VCM disabled!
 
#2 ·
Combination driving nets 20-23 MPG in lovely central Oregon. When we lived above L.A., combo mileage was 19-21, since more AC. I could easily get the mileage you share with some more aggressive pedal.

Drive like you have raw eggs in your shoes. Make sure the instant mileage display is up so you can see the effects of your pedal inputs. Brakes are the enemy of fuel economy -- every slowdown demands some acceleration. Do whatever you can with the throttle to allow the transmission to upshift as soon as possible. Lots of little things combine to steal fuel as you drive. A feather-foot helps a lot.
 
#3 ·
Make sure you don't have a dragging brake.

I was actually able to exceed the stock highway MPG spec with VCM disabled in my Accord. Official highway spec is 30, I got more like 34-35.
 
owns 2006 Honda Odyssey EX
#4 ·
About 21mpg mixed. Check your tire pressure, don't want it too low. Check tires, maybe need an alignment. Switch to synthetic oil if not already doing so. Check drive belt for any squeaking due to pulley going bad. Check brakes and wheel bearing drag by driving and then coasting to make sure it doesn't stop too quick by itself. Transmission oil changed?
 
#5 ·
I have had VCM Muzzler installed for the past 3 years on my 2012 Pilot Touring 4WD and usually end up getting around 12-14 mpg combined between highway and city driving in Los Angeles.

What MPG range is everyone else on here getting with VCM disabled?

It feels like my MPG is low for what I probably should be getting and am trying to go about figuring out how to improve.

Additional Info on my Pilot:

  • It has a 2" spacer lift on it
  • 2 small oil leaks from the rear main seal and oil pan, which result in 1 drop on the driveway per month, so not a big leak.
  • Spark plugs were replaced <2 year ago (Denso Iridiums) and just inspected and cleaned last weekend. No oil fouling or oil in tubes or coils.
  • PCV valve was replaced when VCM Muzzler installed.
  • Have not replaced EGR yet but have a new one on hand. There are no indications that it's bad.
  • Had a check engine light come on last weekend (P0420) which I think was due to a pretty big tear that had developed in the air intake boot, which I promptly replaced, and seemed to fix the issue.
  • The engine runs and sounds fine with no knocking or rattling.
  • Air filter is new.
  • Here are pics of my pilot: https://instagram.com/familykuruma?igshid=YmMyMTA2M2Y=

Thank you in advance for sharing the MPG you all are seeing with VCM disabled!
18.2 over 5,000 miles mixed city and highway, SVCM, 2015 ex-l
 
#6 ·
Thanks for the tips. Sounds like you all are able to achieve or get better than the factory mpg spec with VCM disabled and conservative driving habits.

I am pretty conservative with driving and usually try to get the Pilot into the highest gear quickly on the freeway and I always have my instant mileage display up to make sure i'm coasting in the 20-30 mpg range. Maybe my initial acceleration is too quick? I also drive with the AC turned off and either vent on or windows cracked open a smidge, when my kids aren't in the car which is close to 50% of the time.

Wondering if there's anything operationally that people have run into other than the normal spark plugs, air filter, pcv valve, bad EGR that they've found helped improve mpg. Wondering if I'm missing anything.
 
#7 ·
Thanks for the tips. Sounds like you all are able to achieve or get better than the factory mpg spec with VCM disabled and conservative driving habits.

I am pretty conservative with driving and usually try to get the Pilot into the highest gear quickly on the freeway and I always have my instant mileage display up to make sure i'm coasting in the 20-30 mpg range. Maybe my initial acceleration is too quick? I also drive with the AC turned off and either vent on or windows cracked open a smidge, when my kids aren't in the car which is close to 50% of the time.

Wondering if there's anything operationally that people have run into other than the normal spark plugs, air filter, pcv valve, bad EGR that they've found helped improve mpg. Wondering if I'm missing anything.
Could always clean the MAF sensor. Won’t hurt.
 
#9 ·
I'd love to be able to get 20 mpg. Mine is 4WD but should be functioning in 2WD for almost all of the time since I'm going basic highway/city driving.

Has anyone run into any issues with their transmission leading to low mpg? My pilot has 165K on it and I'm wondering if it's something like the transmission or torque converter that's not working well.

I did a 3x fluid change a year and a half ago and have been doing a 1x change with every oil change just to keep the fluid relatively fresh.
 
#10 ·
At 165k it wouldn't surprise me if you had an O2 sensor or two not at peak performance.
 
owns 2006 Honda Odyssey EX
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#12 ·
That could be a sign of running rich, which could be for a number of reasons.

The way to verify optimal O2 sensor operation is to use a scan tool that can read fuel trims and make sure that the fuel trims are within the acceptable range.
 
owns 2006 Honda Odyssey EX
#14 ·
Consider...

Mixture adjustment, as 'fuel trims', are totally dependent on how well the upstream oxygen sensors are performing in closed loop operation. They also seed the maps that guide mixture in the open-loop operation before the sensors heat up and start generating good readings. "Good" is a relative term, as there's really no onboard way to validate the readings. Closest is that as upstream sensors get weak, you might get a cat failure code especially if the downstream sensors are still reading accurately. Else a second bung for a broadband sensor and related analyzer with datalogging costs more than a set of new sensors anyway, so why go through all that?

Has you car experienced VCM operation and particularly VCM-related blowby and misfire? The extra oil and unburned fuel will trash both the sensors and the catalysts. There are some pretty simple vacuum-gauge tests you can do to ID partially clogged cats. You can also look at MAP sensor data with an easy OBD datalogger to help with that; easier and no plumbing involved.

Our Pilot is in the ~~60k range so the sensors are still working OK. But I do track fuel consumption religiously, and can see when things start to fall off. Real comparative testing is in summer with decent and consistent warm-up times, and we are on "summer" fuel blends. FWIW, on a couple other cars in the fleet, weakening oxy sensors show up earlier, and the window of economy-driven replacement shows up around 50k. That's with upstream-only sensors, so the replacement cost is half. But... we only add 3-4k to the Pilot each year now, so it takes a lot longer to pay for a full set of sensors based solely on fuel savings. Drive closer to the 15k average annual miles, and the economies are a lot more apparent. If you can DIY the install, look hard at new upstream oxy sensors.
 
#15 ·
You said 2" lift... does this mean larger than stock tires?

The 2nd gen Pilot can get really good mileage (mid 20's) on the highway but it is a little underpowered and larger tires and/or heavier wheels (I have both on ours now) take a big toll on fuel economy.

Our '15 is an around town rig most of the year - somewhere between combined and city style driving. We were getting 17ish and since the new wheels and tires that are larger and heavier we are around 15ish. My wife enjoys having a V6 and is not afraid to hear it sing.

IMO, and I've been on SUV forums for almost 20 years now, your mileage is normal. I think you'd smell a dragging brake (you can always check the rotor temps with a laser thermometer after driving for a bit). MAF sensor is easy to remove and clean, so that's always worth doing. I've heard some claim replacing O2 sensors at 100k helped with mileage but I've never done that and comment on it.
 
#16 · (Edited)
Carrying the bigger tires thought a bit further -- larger diameter tires affect the odometer reading, displaying fewer miles than it will with stock diameter tires. If you are watching the onboard mileage display, it will certainly show poorer fuel consumption numbers with taller tires. Tire Rack offers some handy data for lots of different tire brands. Look hard at the "revolutions per mile" numbers for original vs. your installed replacements, and use that to determine an odometer correction factor, the ratio of original revs/mi to new tire revs/mi. Adjust your calculated MPG numbers by that correction factor, and you'll be a bit closer to the truth.


----
TL;DR --
My vintage Garmin GPS unit has options to track miles driven along with some other critical data like max and average speeds between resets. If I had larger tires installed, I'd grab that data and compare it with the speedo and odometer readings from the car itself, and get an idea of a correction factor to apply to each. I find that the readings from the car are about 6% optimistic for both. Translated to real life, that means the car is travelling about 47 MPH when the speedo displays 50 MPH. ODO similarly logs more miles than what shows on the GPS, by a similar factor. Most decent smartphones can use a GPS map application that displays speed, something you can use to at least get an idea of how accurate your displayed speed readings are while driving. IIRC the allowable error from the factory is 5% with new tires on it, and that error will change with tire wear and also inflation pressures.

While we don't generally consider the Pilot to be anything close to "aerodynamic", aero drag is a force to consider. The coefficient of drag, C-sub-d, is the relative efficiency of the shape as it travels through the air. To estimate total aero drag, you get to multiply that drag coefficient by the effective frontal area of the car. With the car raised up, that effective frontal area increases. So the total aero drag numbers go up too. Remember also that friction losses escalate at the square of the increase in velocity. That includes aero and mechanical losses. With taller tires and driving at an actual NN MPH, those losses will be 4x at 2 x NN MPH.
 
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#27 ·
Well holy shit! After reading the first post, I was about to give my VERY unscientific version of this...glad I read through some of the posts. What a well thought out response,I've never seen the actual calculation...thank you Dr. Bob!

As someone who's lifted/leveled my last three trucks, and added substantial weight and size through various wheel/tire combos, I would think that your (ryebread) MPG drop is being affected in this area, more than any other. Assuming you're using the BF Goodrich Terrains in a 235/60/18 setup (your instagram pictures are great btw, nice looking rig!), they clock in at 35 lbs per tire. The original Forteras (that I'm assuming they used in MPG calculations back in 13') were 30lbs a piece. 20 lbs shouldn't net a substantial difference, especially with width/circumference being the same.

The 2" lift would appear, to me, the biggest culprit here. It would be even worse if you have an oversized tire.
 
#17 ·
I am about 75% city and get 18. On the highway get 22-24. I am FWD 2012.
 
#18 ·
My 2012 EX-L 4WD, with VCM disabled, is getting about 16.5 as reported on the dash. All around town driving. Highest I've seen is maybe 19 on a highway trip. I bought the vehicle with 150k and had to replace the upstream rear converter... likely trashed by 150k with VCM enabled. But with a new cat, plugs, vcm disabled, she's running great and not using any oil. Also FWIW, as part of my post-purchase maintenance, I did the valve cover seals, which showed me a lot of sludge up in the valve train. Unclear if the prior owner did frequent oil changes. Cleaned out the valve covers (pro tip - don't throw them in your dishwasher if you don't want your wife to be pissed), replaced the PCV (it was fossilized in and came out in a lot of little pieces). Ran it with synthetic for 1000 miles, changed it, ran another 1000 miles, flushed with Liqui-Moly 2037, and have now run it maybe another 4000 miles. After the liqui-moly flush my mileage came up almost a full point. All 4 brakes were done and aren't dragging.

Will see where it goes from here. But for me - around town driving, michelin all-seasons, I'm getting mid 16's.
 
#19 ·
which showed me a lot of sludge up in the valve train
I wouldn't be too concerned, the front head commonly gets sludge buildup on it (more than the rear head) because of the PCV system, and considering how old your PCV valve was, that probably didn't help things.
 
owns 2006 Honda Odyssey EX
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#20 · (Edited)
Getting 16.2 mpg reported on the dash. Before VCM installation about 17.5. Most of my driving consists of commute to work - 11 mile round trip, plus a few miles running errands. Predominantly city and congested freeway driving, short commute, AC on 50-80% of the time. I give it the beans about once a day, love the sound & feel of the V6 stretching it's legs, so no prius driving here. A 2011 Pilot 2WD, 62k.
 
#23 ·
The only downside I've noticed is reduced MPG since you're using all 6 cylinders at all times.

Update on my MPG. I drove this past week from a full tank as if it were the last tank of gas on earth and was able to get my average up from 12-14 mpg to around 16 mpg.

My check engine light also came on with a P0420 code and my short term fuel trim also clearly got worse (see attached), where both banks are now idling at -12% to -15% from the other week when they were idling in the -4% to -6% range. @WiiMaster @dr bob I'm planning to replace my upstream O2 sensors this weekend to see if that helps out. What I can't figure out is why both banks got affected at the same time. If one of the O2 sensors was bad, wouldn't I expect to see issues in only one of the banks? What are the odds that both upstream O2 sensors went bad at the same time?
 

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#24 ·
There are a lot of things that can cause a P0420/P0430 (though the most common causes are O2 sensors or the catcon). Have you ensured you don't have any issues like a torn intake hose or anything like that?
 
owns 2006 Honda Odyssey EX
#25 ·
The same P0420 code was thrown a few weeks ago and turned out I did have a torn intake hose. Tear was pretty big in an area I didn’t notice. Bought a new one and installed, cleared the code, and it didn’t come back on. Then just came back on again 3 weeks later so assuming it’s a different issue.

I don’t have new O2 sensors on hand and Autozone and Orielly are twice as expensive as online for OEM, so just ordered from Rock Auto. Had a can of Seafoam Spray and just ran that through the engine hoping that’ll buy me some time. Cleared the codes and the engine seems to be running a bit smoother plus short term fuel trim has come back down to -5% range.

Still planning to replace the upstream sensors when they come in.
 
#26 ·
Also try driving with a lead foot on the highway for a bit to help burn off any deposits that could be contributing.
 
owns 2006 Honda Odyssey EX
#28 ·
I have had VCM Muzzler installed for the past 3 years on my 2012 Pilot Touring 4WD and usually end up getting around 12-14 mpg combined between highway and city driving in Los Angeles.

What MPG range is everyone else on here getting with VCM disabled?

It feels like my MPG is low for what I probably should be getting and am trying to go about figuring out how to improve.

Additional Info on my Pilot:

  • It has a 2" spacer lift on it
  • 2 small oil leaks from the rear main seal and oil pan, which result in 1 drop on the driveway per month, so not a big leak.
  • Spark plugs were replaced <2 year ago (Denso Iridiums) and just inspected and cleaned last weekend. No oil fouling or oil in tubes or coils.
  • PCV valve was replaced when VCM Muzzler installed.
  • Have not replaced EGR yet but have a new one on hand. There are no indications that it's bad.
  • Had a check engine light come on last weekend (P0420) which I think was due to a pretty big tear that had developed in the air intake boot, which I promptly replaced, and seemed to fix the issue.
  • The engine runs and sounds fine with no knocking or rattling.
  • Air filter is new.
  • Here are pics of my pilot: https://instagram.com/familykuruma?igshid=YmMyMTA2M2Y=

Thank you in advance for sharing the MPG you all are seeing with VCM disabled!
I noticed in Instagram that you are running Carplay in your Pilot. May I ask what device are you using to make this possible or is it the Navtool ?
 
#29 ·
My '09 at 177k is the same as everyone else, basically.

Have P0420/P0430 off and on. Last year I replaced plugs/cleaned MAF/replaced PCV/changed air filter/tube. Always use synthetic oil, and drain/fill ATF a couple times a year, only Shell/Chevron/Costco gas.

Best thing for the C/E light is driving on the highway, usually I'm only going 10 miles per trip at most, a lot of smaller trips in the city maybe a mile or two at most.

I have somewhere around 16-17mpg. If I drive on a long trip and don't go 85mph, I get around 25.

I also got new tires but still need to have an alignment done, the rear camber needs to be repaired.