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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
This is still confusing, do I read this right? the VCM is better in the city and the non-VCM gets better mileage on hwy?
First, VCM is very unlikely to kick in during city driving (if ever) and the whole point of it was/is for hwy running when it can kick in.
My experience is VCM only kicks in during steady running above 30-35 mph and even then it drops out at the slightest upgrade (avoid the cruise control if you want max VCM). Also, my mpg clearly improve with hwy driving when VCM is available.
Maybe the chart numbers are just reversed.
 

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Here's how you improve mileage: install taller tires on the back of the vehicle; that way, you're always traveling "downhill"...
 

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In reply to lori_cohen, despite what I put in my earlier post, if you are experiencing excessive shoulder wear on your tires then, sure, you should increase inflation pressures, and maybe 3 psi is insufficient. Remember, if you are setting pressures after driving to a gas station you need to add extra pressure anyway to compensate for the temperature rise in the tires incurred by driving to the gas station, so in total you need 3psi maybe for the temperature rise and another 3 or more to try to even the tire wear. Regarding fuel consumption versus speed, the air resistance of your vehicle increases with the square of the speed, so the effect of speed is pretty dramatic, especially at speeds above about 55 mph (88km/h).
 

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Discussion Starter · #24 · (Edited)
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.
I'll do this and get back to you. Meanwhile, I just Seafoamed the engine, using a spray can of Seafoam in the manifold and another can in the tank. I also set the tires at 40psi. On a 1,000 mile trip over the past three days, I drove three different ways to see the impact on mpg.

Driving away from home, I seldom drove faster than 69-71mph on the Interstate, but I'd pick up speed on the downhill to 75 or so and slow gradually on the uphill to keep the transmission from downshifting. I also drafted a few semis close enough to feel an effect... maybe 3-4 car lengths back... for maybe 50-75 miles of the 400 mile drive. There were a couple of rest stops, but otherwise it was Interstate the whole tank. I averaged 26.3mpg. Driving like this was a pain. I wouldn't want to have to monitor my downshifts and speed so closely all the time and I definitely don't want to draft close behind semis. I prefer a safer following distance.

Next, I drove around rural Peoria for a couple of days of normal driving. Nothing in town. No really fast starts, but no attempt to save gas either. Then I drove maybe 100 miles on the Interstate at 70mph. I averaged 22.8 mpg on that tank.

Next, I filled up and drove home on the Interstate. Again I drove 70 mph, but I used the AC and made no attempt to draft. I averaged 23.8 mpg.

My subjective opinion is the the Seafoam treatment made a very slight improvement in gas mileage of about 1 mpg, but I need to check mpg on my daily routine to see if there was really an improvement.

Rexki's suggestion to lower the van with aftermarket shocks and struts is a novel idea. I've been thinking of replacing the shocks and struts and since I don't need a lot of clearance where I drive, this might be worthwhile. I certainly want to make sure my aftermarket shocks don't raise the vehicle higher!
 

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WillowTheDog - remember you'll need lowering springs too, strut & shocks won't change the height of your vehicle. The better aero as a result of lower body height should help with fuel economy.
 

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Discussion Starter · #26 ·
After another tank and a half, the Seafoam treatment improved MPG by about 1 MPG. I'm now getting 22.8 rural and between 23.8 and 24.1 on the highway traveling between 68 and 75 MPH.
 

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Traveling at 65mph rather than 78mph, gives me approx 4-5 mpg more.
Big difference in the mid 60's rather than the higher 70's.
But, I still drive in the upper 70's on the freeways with the higher limits (I just keep the AC off then). :eek: :)
Buffalo4
 

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Try Ceratec. A engine additive that help a little bit like +2mpg for 30k. There are few threads on this site covers it.
 

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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.
@John Clark, could you please take a look at my numbers?

2006 touring, 192k miles, new denso o2 sensors:

1) Idle RPM, coolant temperature 76 degrees Celsius
ST Bank 1 6.3%
ST Bank 2 3.9%
LT Bank 1 4.7%
LT Bank 2 0.0%

2) 2500 RPM, coolant temperature 76 degrees Celsius
ST Bank 1 5.5%
ST Bank 2 2.3%
LT Bank 1 4.7%
LT Bank 2 0.0%

Are these numbers ok or no?
Can they increase fuel consumption noticeably?
 

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Don't speed, avoiding areas with heavy stop signs if you can, keep up with oil changes, remove excess weight. And make sure your tires are inflated to the correct psi. Under inflation reduces gas mileage.
 
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