oxygen sensor replacement?

Yes, but it could be a lot of things. Throttle position sensor, ignition, dirty injectors, vacuum leak.Get a code reader and see, first. Fix what code indicates. Then, as a matter of routine, look for vac leaks, use some injector cleaner, change plugs, check spark,spray TPS with cleaner. Try cheap stuff , first. I've seen quite a few suspect O2 sensor "first" and find that wasn't it. The price of a new sensor still adds up to almost 100 gallons of gas, even nowadays.

The oxygen sensor does control the air/fuel ratio. Replacement of the O2 sensor should be done only if the sensor tests bad. Diagnosing for any problems would be a better course of action and less wasteful of dollars. If maintenance has been lax several other items might be causing the poor mileage. Spark plugs, Injector cleaning, air filters might be items to look at for mileage improvement.

A 95 F250 with a 7.5L is going to get awful fuel mileage period. Changing an O2 sensor on a whim isn't going to change a thing. Clean injectors, new tune up parts and a clean air filter might help a little. What will really help is NOT pushing the vertical pedal on the right :-)

An oxygen sensor replacement would improve the mileage on a 2007 F250. You have a 95 F250 with God knows how many miles, engine issues, differential and transmission worned out, etc.

If the gas mileage bother you get another truck. Don't invest $300 at the time in a clonker.

There are too many other reasons for poor gas mileage to blame it on the oxygen sensors. It's better to spend your money on diagnosing any engine misfire or engine too rich problems in my opinion. The O2 sensors simply tell you how your engine air to fuel ratio is performing. It's true that they can need replacement, but many times they are replaced when they're not bad. It's worth a diagnosis by the Ford dealer to see what their shop says as long as your dealer has a good reputation.

You also need to reset your odometer trip mileage to zero when you get a full tank of gas. Then drive until you fill up the tank again. Record the number of gallons used on the gas pump. Divide the number of trip odometer miles driven by the number of gallons used to get Miles per Gallon. Do it several times and save the results to show your dealer's shop.

By awful fuel mileage what do you mean? At best this truck 18 mpg on the highway, if you're not carrying a load. You could get as bad of 9 mpg or LESS if you have a load on. So first what is your fuel mileage? Then we can talk.

if the oxygen sensor is bad or getting there, it can indeed reduce your MPG's by as much as 40%.

oxygen sensor should trigger the check engine light.

you would probably notice a sudden increase in power, like you pushed the pedal in more, somewhere around 3,000 rpm as you accelrate.

oxygen sensors tell your computer if they are adding the correct amount of fuel, oxygen sensor failure usually means its gotten "lazy", slow to react. you begin accelrating and its not giving you as much fuel as it should, get up towards 3,000 rpm and the oxygen sensor finally wakes up and lets the computer start adding more fuel.

keep it in a lower gear and gently accelrate until you've gotten to 4,000 or so rpms before allowing it to shift. if the oxygen sensor is bad you'll feel it.

a multimeter can also test an oxygen sensor very quickly. an oxygen sensor generates its own voltage based on a chemical reaction caused by heat and differing amounts of oxygen on either side of it.

its very low voltage, but very readable with a decent multimeter.

older oxygen sensors only have a single wire and depend on the exhuast to do all the heating. they can take as much as 5 minutes to warm up. newer ones have three wires, 2 of them are to supply power and ground to electrically heat for a quicker warm up.

just probe the signal end with it warmed up and the motor idling. snap the throttle, give it a quick rev and let it return to idle. the multimeter readings should respond INSTANTLY to the increase in rpms and INSTANTLY as the rpms begin dropping back to idle.

oxygen sensors can range from about $50 for a "universal" one at an auto parts store that MIGHT work, and wont easily be returned after installing and finding out it doesnt work. or it can be as much as $300 at a dealership.

its about as simple to replace as it gets. you really will find you MUST have the special oxygen sensor socket with a cut away side for the wires to stick out. but unscrew it, coat the threads of the new one with anti sieze (VERY IMPORTANT, it will NEVER come out again if you dont) and screw it in. connect the wires, a dealership part will just plug in to the factory wiring harness, and it should be all good.

BUT, its not a light duty truck or an economy car, and the 7.5 isnt a small fuel effecient engine.....

i had a chevy with the 454 in it years back, freeway mileage while drafting on a semi was 9.5 mpg. in town 5 mpg wasnt bad, floor it and you could almost see the gas guage dropping.

under 10 per gallon on a vehicle that required premium and gas prices had surged all the way to $2.15 per gallon for premium, i sold my older truck and bought a more fuel effecient one that is just as capable but gets 16-20 mpg and only requires regular.

and they are just getting more and more fuel effecient.

if i bought another new truck today, i could be getting about 18 city 23 fwy mpg. at $4 a gallon thats a BIG difference.

if you really want to seriously improve your fuel effeciency, shop around and decide which new truck you like best. you can get all the capability and save money on gas. with todays gas prices and what a big truck can cost to fill up, you could possibly make a good portion of the monthly payments with what you save at the pumps.

That makes sense however your check engine light would come on if they were truly bad. It could not hurt anything but your pocket book though. O2 sensors are a maintenance item like a fuel filter ETC. I would try looking at your spark plugs first however as if they are worn they will eat into your fuel economy dramatically

Hi

Lets just look at what we have here:-

A 7.5 litre petrol engined truck

Bad fuel economy

Unless you are inferring that the fuel consumption has gotten worse over time then I can't actually see a problem here, because even running perfectly, the fuel economy from a massive engine like that is going to be atrocious at its very best!

Very best regards

Geordie

Only if you first test the O2 sensor and it fails. Randomly changing parts on bar room advice is a fools pursuit.