Help with mileage

[Rockman]

I think im getting horrible mileage in my "new" Quigley. 6000 miles, 5.4 Ford. 12 is the best I have gotten so far. Driving mostly highway, and 55-65.

It can with 285/75R17 with I know has to decrease the on-road performance, so Im thinking of going down to a BFG AT 245/75, since it is lighter and a little more highway ready.

It would be awesome if you guys could give me a little help.

1) just how much would the smaller/road AT tire gain me?
2) what other addons, could I use to stretch my mileage?

Im going to get the scantool for better driving, but what about chips,exhaust,plug wires, coils and that sort of thing.

Any help would be great.

[geoffff]

I haven't heard any reports that the 5.4 gets significantly better mileage than the 6.8 v-10. 12 MPG at 55-65 MPH is at (or slightly better than) what I get (v-10 gas, 4x4).

-- Geoff

[geoffff]

I'm not an expert on what going to smaller tires will do, but unless you change the gearing too, you'll be revving the engine faster for the same highway speeds, and that could cost you more gas (engine friction) -- that is, unless you find yourself downshifting all the time with your current setup.

It sounds like you know the basics, but my thoughts are that regardless of engine, you're stuck with your Sportsmobile being unaerodynamic (hurts highway driving) and heavy (hurts low speed driving).

Highway driving -- it isn't fun driving slower (and I don't do it), but if I happen to find myself going only about 50 MPH, it makes a huge difference. The van encounters fantastic wind resistance, and the power needed to push any vehicle though that air goes up with the cube of the speed (power needed = aerodynamic-constant x speed x speed x speed). With my gas V10, I can get <8 MPG at 80+ MPH, and up to 13 at 50 MPH.

Low speed driving -- the biggest factors here are avoiding having to use the brakes (every time you hit the brakes you're wasting the momentum you burnt all that gas to build up). That, and trying to stay in the highest gear possible.

Engine revs -- Yes, get a Scangauge. I use it to watch the engine load. When climbing hills and the engine load gets above 90%, I know the van is about to downshift if I press the gas pedal further -- so I can hold back on the gas if I don't mind slowing down a bit. The Scangauge also shows instantaneous MPG, so I can see exactly how downshifting makes a big difference in MPG (drops by something like 25% when the van is in 3rd gear instead of 4th on the highway)

-- Geoff

[Greg In Austin]

Well said Geoff,

As a hybrid driver, I agree.

Probably the two biggest things you can do is reduce your highway speed. We drive 55mph even on the interstates.

...and try not to use your brakes. THis means you need to drive farther ahead, watch farther ahead. Anticipate stops and let off the gas earlier.

For our hubrids tire pressure and oil fill are also very important. Keep the tire pressure high and DO NOT overfill the engine oil. Surprisingly the engine oil overfill hit us for 3 to 5 mpg.

[daveb]

Rockman I think your mileage looks OK as Geoff said. Has it decreased? Taller tires will give you slightly better tires but will also slightly reduce your power. I don’t think it’s worth it for the reason of better mileage. Is your van running rough? With a gas engine it’s critical that the plug wires aren’t cross firing or grounding out. I always try to keep the wires clean and clear of contact by adding a rubber protector to areas they cross each other or where they touch hot metal especially manifolds…etc.
Have you changed your fuel filters? Maybe you got into some bad fuel. I was surprised to see how dirty my (gas) filters were after 10K. I don’t like fuel additives in my diesel but with a gas motor I have had good luck with them.
I did change to AMSOIL and gained a mile or more per gallon.
I won’t use special air filters or performance chips but do plan to install a selectable chip after my warrantee is up and run it in short bursts when needed.
What does your van weigh? If you’re driving in the hills weight can be a factor. I can tell when I bring extra people and equipment. After you install your Scan gauge, document the mileage on a typical run and tweak things (such as the weight) to see if you gain any mileage driving the same run. With all that said you might not even have a problem and tweaking the weight and good driving habits like Geoff said should produce good results. Welcome to a world of high priced fuel that doesn’t have to be.
Dave

[Rockman]

thanks all for the info. The scantool will def help watching shifts. As I am used to manual trans.

Losing power is not a concern, and these tires are very heavy and keeping them rolling has to be hard to keep going. I had a similar problem upgrading my cj7 with crazy big tires.

But taller tires may not be an option, an I have major fender rubbing currently.

I'm def going to check my plug wires, as well as amsole.

Thanks again.
Rockman

[Ford_6L_E350]

Originally Posted by Rockman

I think im getting horrible mileage in my "new" Quigley. 6000 miles, 5.4 Ford. 12 is the best I have gotten so far. Driving mostly highway, and 55-65.

It can with 285/75R17 with I know has to decrease the on-road performance, so Im thinking of going down to a BFG AT 245/75, since it is lighter and a little more highway ready.

Mileage changes from changing tire sizes may be an illusion. Unless you recalibrate the speedo for the size change. The taller tires you have means you travel further than the odometer indicates, and your mileage is better than you calculated. Putting smaller tires will reduce the effective gearing and make it seem like you are getting better mileage. Unless you start lugging the engine, reducing the engine speed will almost always generate better fuel economy. But, remember you are only talking about a few percent, probably less than 1 mpg.

Get a ScanGauge

http://www.scangauge.com/

and calibrate it. It will give you fairly accurate mileage readings. You can calibrate the speedo reading and the fuel consumption.

[Greg In Austin]

The ScanGuage will make a difference. I would speculate that it would make a difference even if not calibrated well.

There are studies underway about how just knowing what fuel economy you are getting affects the way we drive. SOme ar refering to this as the 'Prius effect'.

It seems that when you have a constant reminder of your fuel economy, instantaneous and average that the awarenous allow syou to modify your behavior and drive in a more economical fashion.

We mounted out Scan guage just to the right of center of the steering wheel on the top edge of the dash so that it is there for the driver to see, and the driver does not have to move their eyes off the road far to see it.

This has made a big difference for us in the Prius and the Insight, and now McBeast.

.

[lactic]

I just got back from a trip from Boulder to Fruita, Colorado for the weekend. Overall, we averaged 14.95 mpg with 15.4 going out and 14.5 coming back as per the Scanguage. We were loaded with 3 people, 3 dogs, three bikes and had to go over Vail Pass and the Continental Divide.

Very happy with my mileage thus far and I definitely find myself driving like a Prius owner!

[geoffff]

That's pretty stunning gas mileage for the gas V10 -- good job! I have never come close to that.

-- Geoff