Accurate fuel mileage readings

Ford_6L_E350 · 07-06-2007, 10:56 AM

While talking to friends at work, it became clear that not everyone can get accurate fuel fillups, especially with Ford diesels, pickups and vans.

The Ford fuel tank has a vent that gets covered with about 4" of the tank not filled. Maybe the purpose is to allow some room for the fuel to expand, or maybe not. But, after the vent is covered, diesel 'foam' comes up the filler neck and causes the pump to shut off. When that happens depends on the fuel delivery rate and how level the vehicle is and probably other factors, like brand of fuel.

As far as I can tell, there are only two ways to get consistent fillups:

- Fill the tank past the 'foam' point, until fuel is visible in the filler neck.
- Use slow delivery and the automatic shut-off will be pretty consistent.

Filling the tank past the automatic shutoff has frequently caused a Check Engine Light (CEL) on my van. The light would come on about 150 miles after a fillup and stay on for several restarts. I have to admit - it was my wife that actually noticed the connection to the fillups.

Now I run the pump on the slowest setting on the handle and the amount the pump says agrees with my onboard computer (Scangauge) quite well - frequently within 0.1 gallons.

Because there are variations in pump speed and how level the van sits when filling, I don't pay much attention to any single tank. Usually a tank with very high mileage was followed by a tank with very low mileage. That simply means the first tank was underfilled and the next tank took the amount used plus the amount that was underfilled at the previous fillup. I watch mileage over 3-4 tanks to see trends. I record every fillup in a logbook.

I also watch the fuel gauge. With my 46 gallon tank it takes about 150 miles for the gauge to come down to the 'F' mark. Each 1/4 tank after that takes about 100 miles. If the gauge drops faster than that, either we are using more fuel because of conditions (in town, high mountains, 4wd low, pulling a trailer) or I didn't get the tank full (which only affects the 150 miles to 'F').

When I put the Scangauge in my van, the mileage slowly went up as I noticed the conditions that caused high consumption and adjusted my driving habits. Overall I've averaged 16.53mpg over 45K miles. I've never had a tank over 20mpg, but have gotten down below 12mpg with slow off-road driving.

Mike

canyonclan · 07-06-2007, 10:20 PM

Mike,

Thanks for that informative post.

I am curious what folks got, on average with their SMB 4x4 6.0 PSD and your info helped out. Our SMB 6.0 is on order with an August delivery in Fresno. I figure that I get about 15-17 hwy on my Discovery II and my wife's Subaru 4 cyl turbo gets a lowly 18-20 hwy.

I'll be a happy man if our10,000lb rig gets 16+ mpg...

-Jeff

**daveb** · 07-12-2007, 01:00 PM

Mike, if I try to deliver fuel slow like that it will overspill on the ground creating a strong diesel smell coming into the van while driving. SMB said this was normal and not to overfill the tank. I usually set the handle to its lowest setting and let it click off by itself. Then I can slowly get about 3 gallons in but I don't push it. Last time I overfilled I had to drive 40 miles to find a car wash and clean up the spill because the vapors were so bad

. Are the tanks different? DaveB

Ford_6L_E350 · 07-12-2007, 01:29 PM

Dave,

When you say the tank will overspill, do you mean the fuel runs out of the filler neck as you are filling the tank, or do you mean the fuel will come out after you put the cap back on the tank?

If the fuel runs out as you are filling, the answer is to stop before it runs out.

If the fuel comes out after you put the cap back on the filler neck, then you have a leak. That shouldn't happen and you need to get it fixed. Maybe the tank is vented to the atmosphere? Again, that shouldn't be. The tank should be sealed, both the keep fuel and fumes in and to to keep anything else out.

Mike

scatter · 07-12-2007, 02:08 PM

When I ordered my SMB earlier this year, I talked to them about the concerns others have posted re not being able to compleatly fill the tank due to the location and depth of the vent tube in the tank. (See Bagers web site for a good write up on this) I asked them to cut off my vent tube before installing the tank and they said that it isn't necessary anymore. Since the beginning of '07 they have modified the new diesel tanks and they fill right up to full. I've checked mine and have had no problems there.
For you folks with earlier rigs, you might want to cut off the vent tube as per Badger.

geoffff · 07-16-2007, 07:50 PM

I have a 2004 Ford E350 with a gas engine, and had related problems with my gas tank. It was sold as a 47 gallon tank but would only fill to 37. Long story short, after several failed modification attempts involving dropping the tank, I had my local mechanic drill, tap, and add a second breather tube. Works now.

-- Geoff

JoeyNick · 07-16-2007, 09:15 PM

Quote:

Originally Posted by daveb

Last time I overfilled I had to drive 40 miles to find a car wash and clean up the spill because the vapors were so bad

If you have an on board shower, use the hose to rinse off the fuel tank area. A baby wipe or two also helps with the spot washing.

kzemach · 07-17-2007, 07:57 PM

Quote:

Originally Posted by scatter

Since the beginning of '07 they have modified the new diesel tanks and they fill right up to full. I've checked mine and have had no problems there.
For you folks with earlier rigs, you might want to cut off the vent tube as per Badger.

So if mine is an '06, that leaves me, uh, irritated? Did they assume that the Badgers' website is required reading? I would not have been happy if I'd run out of fuel prematurely. I guess I'll have to check that too.

Perhaps it was also done correctly on mine, as it was late '06. Did anyone with, say, an '05 with the 46 gal tank get a call from SMB telling them that their 46 gal tank didn't hold 46 gal?

geoffff · 07-18-2007, 12:17 AM

For my 2004 Sportsmobile (gas) with the oversize TransferFlow fuel tank option, the gauge reads Empty when the tank is empty. (I found that the gas engine will start stumbling when you're minutes from running out of fuel.) When I fill my tank all the way, my gauge is pegged at "Full" until I burn the first 10 gallons of gas.

For some reason, this is not the behavior Sportsmobile told me I should have. They said it should immediately start decreasing from Full, and then read Empty for the last 10 gallons.

-- Geoff

scatter · 07-18-2007, 07:32 AM

Geoff - My gage is pretty much the same as yours. It stays on full for at least the first 100 miles. I haven't run it till it stumbles, but when the needle and the red empty mark line up I can put 42 gallons in it. That's low enough for me. I prefer to choose where I hike, and it's not along the freeway.