I've got a 98 F150 with the 4.2 V6, its got 220k on it. I've got magnaflow high flow cats, muffler new brakes, ball joints, fresh allignment, tires and tune up... I get about 450 to a tank (95L) driving normally which is about 19-20L/100k... is that right? they replaced the 4 cats with 2 and said that would be better for fuel economy... could they have maybe forgot to reset the o2 sensor?

 

Yea I get about 15.5 mpg in my 4X4 4.2 F-150, 20mpg is good.

 

my 02" 4.2 only gets 325 miles on a full tank..3" body lift 35" tires

 

I've been averaging 22 mpg... if I set my scan gauge to current/realtime mpg, I'm getting like 23.X mpg in some situations.

It's nice.

I just hauled a whole bunch of computer equipment today, and I dropped only down to 21.2 mpg with a load of about 1500+ lbs of computer equipment..

 

I'm in the middle of a cross country trip, and I'm getting between 18 and 19 mpg so far on **** winter gas, cruise set between 70 and 80.

 

Average MPG

16.5


State

CA


Stop & Go

55%


Highway

45%

 

Am I missing something here?

Quick math says you are getting 20 MPGs, which according to my EPA estimate, is doing quite fine considering those figures are 15city/20hwy.

You might have some resonators in those exhaust pipes somewhere, but not four cats.

It's a big hefty full size truck. Not a 4 cylinder Ranger.

And you can't reset an O2 sensor. They are similar to spark plugs, in a broad sense, just tapped into the exhaust pipes. Not much to reset there.

 

You are missing that he is going 450 kilometers per tank, not 450 miles.

My quick math says he's getting under 12 mpg.

FWIW, on low energy content fuel these trucks do not get good city mileage. IMO, anyone consistently getting anywhere close to 20 mpg has good quality (high energy content) fuel, drives almost only highway and has a light foot. And probably has a 5 speed.

If you drive city, and live in an area with bad air quality (with low energy fuel), have a supercab, bigger or stickier tires and an automatic, you will be lucky to get 20 mpg with a tailwind on the highway, and will probably get less than 15 mpg in the city. Maybe only 12 with big tires and an aggressive driver.

 

Yup - I was getting around 14 in the city in California.

 

I have a 98 flareside with the 4.2,5 speed w/214,000 and im getting betwen 8-10mpg.Quite depressing.

Just changed the plugs and they were white.Gonna change 02 sensors next week and im praying it improves.I drive anywhere from 100-500 miles weekly

 

Daves right... I'm in Canada so its Kilometers up here...

I would LOVE to get 450 miles to a tank.

Anybody have any ideas why I'm getting such terrible fuel economy?

 

I'm curious as well, as we may be having the same mysterious problem. My '99 with 122,000 miles does not get anywhere near the fuel mileage it used to get, especially when city driving. I bought it new, and calculate (but do not record) my mileage every tank.

It's like at 100,000 miles, my truck started getting 10% - 15% worse mileage. Since then, I've changed the fuel filter, PC valve, plugs, plug wires, and front O2 sensors. Tires are properly inflated and the brakes are not dragging. Even tried sucking up a can of Sea Foam through the brake booster. The new parts and Sea Foam treatment have given no change in fuel mileage. Motor is not throwing any codes, but seems a little weak.

I'm thinking mabye a dirty EGR valve/system or possibly a dirty MAF wire or the coil pack going bad (all six cylinders are on the same big coil for the'99). But I'm running out of ideas.

 

You guys do know that 1/2 ton pick ups are not economy cars, right? You want to save money on gas? That's what a Honda Fit or Toyota Yaris is for.

If I can knock my $100 weekly fuel bill down to $40, the cost savings would pay for my new economy car.

 

Yea, but when people are getting 20mpg and you get 14. I would want to know whats up also.

I had to spend almost a grand to get my 19mpg, but I also have more power.

 

For me, it's about trying to figure out why my mileage is way worse than it used to be. And for the OP its about trying to figure out why he's only getting about 12 mpg. After 9 years of owning this truck, I think I'm crystal clear on the fact it is not an economy car.