18MPG around town on 03 5.4l

[Prince_Polaris]

I need to remember that because I live in western maryland, my MPG is gonna be lower than all of you guys who live in flat states- everything out here is a mountain!

 

[Jdcline54]

okay.. Sorry it has taken me so long to reply...

So a smoke test is for finding vacuum leaks. because if you have a vacuum leak you have air entering your system after the MAF sensor, which is unmetered air. the computer adjusts fuel/air mixture based on what the sensors have told it, so if you have unmetered air the air fuel ratio is out of line from what it should be, thus creating a lean condition...

That being said, a smoke tester is a machine(that happens to be very expensive) that you hook into a vacuum line or directly into the air ducting that goes up to your throttle body/intake. it's forced in with compressed air to pressurized the system with smoke...then you just stand back and watch for anywhere you see smoke leaking out, and Bam! you know what to fix...

In my case I had smoke coming out from the lower intake area, and the EGR valve. also had some coming out the power brake boost plug but that was fixed simply by pressing it in a little better.

so at that point I knew without a doubt that I needed lower intake gaskets and an EGR valve. once I got the Intake off I discovered that I had a leaky valve cover gasket also. so I went ahead and changed them all... Upper/Lower intake and valve cover, along with the egr.. BOOM 18 MPG! Also I should note, I live in a mountainous region of Utah...So if I can get 18 so can you.

Now as I mentioned the smoke tester being expensive...like $2000... don't worry, I know of a cheaper alternative. dang near free...If you have a little bit of D.I.Y. skill.

Heres a couple links to a diy video for a smoke tester:

I don't really like this one, but its super cheap and easy.

This dude is kinda ghetto, but his method use compressed air rather than a bike pump which would work better, in my opinion.:

 

[Dwilds]

Woah woah woah you're getting 18MPG with the 2003's 5.4L V8????? I GET NINE POINT SIX! D:

I second the 9 MPG. With a newly remanufactured engine.


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[ExplorerTom]

I need to remember that because I live in western maryland, my MPG is gonna be lower than all of you guys who live in flat states- everything out here is a mountain!

The thing about hills though is that going up hills isn't nearly as inefficient as going down hills is efficient. Meaning: if 14 mpgs is a good "flat" terrain average, going up a hill may drop you down to 6 or 8 mpg, but coming down a hill can see 75 or more.

At least that is my experience. Any time I have a tank of gas that includes mountain driving, that tank is always noticeably better than a tank where I stay out of the mountains.

 

[Plati]

The thing about hills though is that going up hills isn't nearly as inefficient as going down hills is efficient. Meaning: if 14 mpgs is a good "flat" terrain average, going up a hill may drop you down to 6 or 8 mpg, but coming down a hill can see 75 or more.

At least that is my experience. Any time I have a tank of gas that includes mountain driving, that tank is always noticeably better than a tank where I stay out of the mountains.

I enjoy math and physics ... so this is a fascinating observation. I don't doubt your experience. Intuitively it seems like it would be a wash, not an increase in gas mileage. Reminds me of riding my bicycle through West Virginia. I would struggle to make it up a steep hill and then coast down the other side. Overall it was a lot more brutal and took longer (for a given distance) than in Kansas.

There are a lot of factors with the mountains in Colorado. Its cooler so maybe you're not running air conditioning at elevation? Air is thinner (and cooler) at elevation so engine combustion "efficiency" is different. Air resistance is also lower at elevation. Might be going slower than on an interstate on the flat? Many factors besides just uphill vs downhill.

If I run the numbers to compare 1000 miles on the flat vs hills (assuming 50% duty cycle). Assume 10 mpg uphill, 100 mpg downhill, 18mpg flat. You end up burning about 55 gallons either way. OK I'm a geek!

 

[ExplorerTom]

I'm also basing this on my observations of the "instantaneous mpg" readout on my OBD reader. Going up the mountain, I'll see it drop to 7ish while flogging the engine: 65-70 mph at 4000 rpm going from 9,000 feet to 12,000 feet over the course of a couple miles. Going down the other side, coasting, it'll read anywhere from 50-90 mpg.

You'd think, based on those numbers, my combined average would be significantly biased to the higher numbers. But if my normal average is 13, a tank with mountain driving might be 15. 2 mpgs isn't much, but it is noticeable and it seems to be repeatable.

If my dad used to walk uphill both ways to school, why can't I drive downhill both ways to work?

 

[Jdcline54]

I'm also basing this on my observations of the "instantaneous mpg" readout on my OBD reader. Going up the mountain, I'll see it drop to 7ish while flogging the engine: 65-70 mph at 4000 rpm going from 9,000 feet to 12,000 feet over the course of a couple miles. Going down the other side, coasting, it'll read anywhere from 50-90 mpg.

You'd think, based on those numbers, my combined average would be significantly biased to the higher numbers. But if my normal average is 13, a tank with mountain driving might be 15. 2 mpgs isn't much, but it is noticeable and it seems to be repeatable.

If my dad used to walk uphill both ways to school, why can't I drive downhill both ways to work?

yeah. I haven't been relying to much on my dashboards instant MPG readout. after I run a tank, or half a tank through and do the actual math I am realistically getting about 17.4 miles to a gallon. and that's with combined, driving nicely and driving like a real a-hole, some in town some freeway/mountain travel.

 

[ExplorerTom]

I always do the math too- or at least plug in the data to the Fuelly app and it does it for me.

 

[1955moose]

Guys our op hadn't stated whether 2 or 4 wheel drive. If 4 wheel drive, I doubt it, best is usually 12 city, 16 highway. 2 wheel will bump about 2 mpg avg. So 13 on a normal running no codes no rich motor. If he's got the smaller 4.6 two wheel drive and drives like your 80 year old granny, yeah he might be able to squeak out 17-18mpg. But he's not having any fun doing it.

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[blue oval guy]

Mileage claim might be a little optimistic