Is it best to replace all for instead of one? My 2003 ford ranger edge with 3.0 has been getting horrible gas mileage recently. The truck isn't lifted or have oversized tires.

O2 sensors today and for much of yesterday are a life of vehicle item; unless they actually fail and subsequently prove bad (ie, trip a DTC) then you leave them alone. Unlike and for example, GM O2 sensors of the early 80's that were scheduled to be replaced every 24,000 miles, the ones used for over 20 years are super reliable and don't have a scheduled replacement period. Doing otherwise is like, flushing money down the drain.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

Ok that's save me $200 in sensors. But what would be cause of my trucking eating so much gas. I'm at a half tank and I only drove 100 miles. I usually get around 270 miles out a full tank.

There's a long list of things that could be wrong. One or more of the systems in that vehicle has gotten restricted in a way that makes it run less efficiently. Could be a rotten vacuum hose, maybe a clogged filter, etc.. You'll need to run some troubleshooting to narrow it down.

Start with the computer. It knows (almost) all. Hook up a good scan tool and pull any codes. If it has any at all, address those first.

Then, check out the maintenance schedule. Spark plugs and wires are good for 100,000 miles. Are yours well within that life? If not, replace.

Fluids? Are you keeping up with the regular oil changes? When was the last time the differential was serviced? Is the air filter still good? Coolant? Transmission?

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2003 Ford Ranger XLT
2.3L I4 Duratec DOHC, 5R44E 5-speed auto, RWD, 7.5" Open w/ 4.10 Ratio, Gibson split-rear catback
Sonic Blue Pearl with dark gray trim

Rear end and transmission had been changed before it hit 100,000 miles. She has 103800 miles now. I maintain her very well. I put in new plugs when I first bought her when she had 60,000 miles. I'll take it in and have the computer ran. But I don't always trust them. Appreciate the advice I'm sure I'll find the problem.

If the vehicle is well maintained, then the biggest influence on gas mileage will be how you use your right foot. Also, it's winter, and mileage goes down in the winter. Lastly, trying to pass judgement on a vehicles mileage by *assuming* it was full and then *assuming* it is at a half tank is no way to get a reliable result. Given that there is an air cavity in the fuel tank for the evap emission system, it's not easy to consistently "fill" a tank. The options for getting around this are a) calc mileage over say, three full tankfulls b) use an ultragauge or the torque app and........it would be good to verify that your odometer is accurate. You can use the markers on the freeway, or better yet, use the GPS on your phone and compare GPS distance against odometer distance.

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2004 Ranger FX4 Level II, 5R55E, Sonic Blue Pearl

Proudly JAP/RICE free since March 2000

For what it's worth, I've seen the needle on my fuel gauge magically increase over short drives during the winter. It may be at half-full when I start a trip, but several miles in, it's suddenly just over half. The accuracy of that gauge is a joke.

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2003 Ford Ranger XLT
2.3L I4 Duratec DOHC, 5R44E 5-speed auto, RWD, 7.5" Open w/ 4.10 Ratio, Gibson split-rear catback
Sonic Blue Pearl with dark gray trim

Mine does that all the time.

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2014 F150 xl 3.7 6 speed auto.