My TJ AWD has just had its 50000 km service. Everything is going well, but I had been noticing for some months that fuel consumption seemed a bit over the top, even for an AWD. I was getting a bit tired of continual readings of 17 to 18 L/100k, when previously for identical driving conditions it had hardly ever been above 15.

My mechanic suggested that the oxygen sensor would be the first thing to replace before fooling around with other investigations. He said they should be replaced about every 5 years, but hardly anyone seemed to bother - the car usually performs fine with or without the sensor.

Anyway, the result was spectacular. After the new sensor was fitted, consumption figures have dropped at least 4 L/100k. At the current price of petrol, I'll have it paid off in 5000 km. No, I'm not after Prius-type low fuel consumption, but at least I'm back to what a normal 6 cylinder car should be.

what did he end up charging you?

as above also interested to know!!

Hey guys. Don't think that fitting a new oxy sensor will be some miracle fuel cutting measure.
As in this case, there was obviously something wrong which Ken solved via a new oxy sensor but in most cases if your fual consumption is round the mid teens then a new sensor will most likely make no difference.
I have changed 3 oxy sensors on 3 different 3rd gen verada's recently, one with 100K on it, one with 120 k on it and the AWD with 150K on it and in all 3 cases, the oxy sensor made no difference to fuel consumption.
My point is, yes, they should be changed at the 100k services but this doesn't mean there is something worng and not to get your hopes up that you will drastically reduce your consumption.

i recently replaced my oxygen sensor with a used cheapie of ebay. My fuel consumption went up 2L/100km.

Regardless of my experience, you might get lucky with a second hand sensor. Just don't use it as basis to cross the o2 sensor off the list as a potential problem. BUT certainly do not buy a brand new sensor unless you have had a recent service and changed the the things that need to be replaced anyway; air filter, plugs, etc.

Just to let you all know I can do GENUINE sensor for $135.00

Generally every 5 years is a good point but also to the above point you need to make sure that your plugs and filters are servicable as well

It cost about $180 to have it fitted.

Because of the low mileage (or should that be kilometrage?) on the car, the plugs, etc are still OK, but the mechanic claimed the oxygen sensors have a "shelf life" of about 5 years before they become sluggish or non-functional. I honestly did not expect too much from this, but felt that something was definitely "not right" with the quite sudden increase in fuel consumption that had seemingly arrived out of nowhere a few months ago.

I fully agree with comments above that fitting a new sensor will not be a miracle cure, but I have to say I am pleasantly surprised at the improvement. At present, the car is settling down to about 13 L/100km for the usual short-haul suburban driving we do most often, and it rapidly sank to 11 on a brief trip up the M4. This is so much better than the rubbish 17 to 18 L/100km I'd been getting the last few months.

hey my car is also doing the same, its going at 17L for every 100kms,

Did the car have a smell before replacing the oxygen sensor?

Where did you get it installed?

from what i have read it looks like it just may be the problem...

I'm not in favour of replacing expensive bits on a "just in case it has failed or is about to fail" situation, be it oxygen sensors or water pumps. Oxygen sensors can be checked with a voltmeter while the engine is running, or removed and inspected. An oxygen sensor with heavy carbon deposits on it is defective. If it is lightly covered put it back in and save your money and look somewhere else for excessive fuel consumption like compression failing on one cylinder or a failed temp sensor. I replaced an oxygen sensor on a car with 240,000 on the clock, it made no difference. Son has a commodore with twin sensors, higher Km than my car, same thing, replaced both, no difference. An oxygen sensor has no moving parts and is designed to withstand a lot of heat, if it has failed it will do so in a way that will show up with a multimeter.

Having said that my sister and brother in law have been known to buy a new car each every 3 years on the "just in case" proposition. lol Takes all kinds to make the world go round I guess.

Just remember the oxy sensor does nothing until the engine has warmed up properly. If you do a 5 km trip to and from work every day the oxygen sensor gets very little work to do. Take the car on the open road and sit on a steady 100 kph for a few hours and look at your fuel consumption then.

Just remember the oxy sensor does nothing until the engine has warmed up properly. If you do a 5 km trip to and from work every day the oxygen sensor gets very little work to do. Take the car on the open road and sit on a steady 100 kph for a few hours and look at your fuel consumption then.

That's right! With a lot of short trips, consumption is still around 15 L/100k, but my original complaint was high consumption regardless of whether the trips were long or short. The new oxygen sensor has definitely had a real effect in lowering consumption in my car from completely ridiculous to at least believable. I simply couldn't hack the constant 17 to 18 L/100k rubbish.

hey my car is also doing the same, its going at 17L for every 100kms,

Did the car have a smell before replacing the oxygen sensor?

Where did you get it installed?

from what i have read it looks like it just may be the problem...

No, there was no smell. In fact, the trouble with a failed sensor is that performance still feels great, so you wouldn't really be bothered if you didn't mind the car gulping more petrol.

My local mechanic installed it. Any service centre worth visiting could do it.

Hi guys,

I'm reading that fuel economy is not real good for some people and changing the oxygen sensor might help. I was wondering...those folk that quoted fuel figures...are those figures from the meter on the instrument panel, or are they actually calculated?

My meter told me my average fuel economy was 9.5 l/110km, but when I did the sums, it was actually more like 11.5l/100km.

Can these oxygen sensors be cleaned? If so, is this something I could do myself?

If these are indeed not working right, do they actually affect fuel economy, or is that a false perception?

Thanks everyone,

Changing the o2 in my Verada dropped consumption from 17L/100km down to 11L/100km average, but then that had a lot to do with the fact it was 180k old and was pretty well shot. Took 4 people to get it off in the end too. It's exactly like Family Wagon said, unless you're experiencing unusually high economy don't expect it to do much if anything, it may, but don't go in with the expectation to cut 40% off your usage. My example with the Verada is just to demonstrate it does do something so if it's not working it's not helping your case.

My meter told me my average fuel economy was 9.5 l/110km, but when I did the sums, it was actually more like 11.5l/100km.

Can these oxygen sensors be cleaned? If so, is this something I could do myself?

If these are indeed not working right, do they actually affect fuel economy, or is that a false perception?

You can't really clean them.

When an O2 sensor fails, the signal the ECU gets tells it the engine is running lean (even when its not) so the ECU keeps richening the mixture up to a certain limit.

The O2 sensors in these cars have a design life of 160000km; while some do fail before then, most will go at least that distance.

11.5l/100km on pure highway driving might be a bit marginal - what fuel are you using?

Hi guys,

My meter told me my average fuel economy was 9.5 l/110km, but when I did the sums, it was actually more like 11.5l/100km.



In all cases, I was quoting fuel computer figures. Even if "actual" numbers were different, the comparison is still valid, assuming that the computer behaved the same before and after replacing the oxygen sensor.

Has anyone managed to find a reliable trend to these sorts of issues. My TL AWD just ticked over 150km and fuel is almost 20L/100km according to my trip computer it would be about accurate too, based on actual pump fills/KM's traveled.

at about 130km it started to climb from the normal 9/12 and has increased consistently over the last 20k... I read alot about O2 sensors but with EFI engines it could be any number of other sensors throwing the balance out too.

The rated life is about 160000km for this type of oxygen sensor - some will last longer, others die before then. If your car has progressively increased fuel consumption over a period of time, the oxygen sensor is likely to be deteriorating. Some cars with oxygen sensors in poor condition don't exhibit signs of rich running other than poor fuel economy; others run noticeably poorly.

In the absence of a way to log the fuel trims from the ECU, the easiest way to determine if the sensor is at fault is to disconnect the sensor, disconnect the battery for a short period to reset the ECU, and then drive the car so as to measure fuel consumption. If fuel economy is noticeably improved with the sensor disconnected, further checking with a view to replacement is warranted - otherwise reconnect the existing sensor as the problem is likely to be elsewhere.