O2's & Mileage

[BackInA88]

Has anyone changed O2's and seen a mileage increase even though they were throwing no codes.
My rig has just over a 100K and I think my O2's are original so I was just wondering if it would be worth it?
I was getting around 14 MPG before with mixed driving.

My mileage has dropped of a bit the last couple weeks, but that maybe if they are selling the winter formulated gas already?


Steve

 

[brianhoberg]

I changed only my drivers front O2 due to throwing a code. Unless the exhaust is smelling rich with gas, I wouldn't think you're losing much fuel within your exhaust.

 

[adriatic04]

getting colder in the midwest too so your engine isnt running as efficiently, isnt that usually the case?

 

[wulfraat]

I had no codes but was getting poor mileage with original O2s @4 years/45k. replaced O2s (all 4) from atlantic british - no difference.

I did sell me used ones on ebay to recover some of the costs.

I wouldn't mess with them unless it smells rich or throwing codes.

 

[sven]

If you have a OBDII reader that can do realtime stuff, you can test the O2s. A lazy O2 sensor could waste gas but not trip a code.

 

[n8thgr8]

I changed only my drivers front O2 due to throwing a code. Unless the exhaust is smelling rich with gas, I wouldn't think you're losing much fuel within your exhaust.

Ditto, if it ain't broke, don't fix it.

 

[smrover1]

If it aint broke fix it and it will be broke. Is always what happens to me.

 

[DeanBrown3D]

Has anyone changed O2's and seen a mileage increase ...Steve

My mileage increases every time I drive. :smilelol:

 

[group captain mandrake]

Sven is right. But you need a quick-reacting (scoping) scanner or, preferably, an ocilliscope to observe the signal switching frequency from the O2 sensors (and it helps if you know what to look for). They do slow down with time and will affect fuel economy from marginal to significant degrees before the ECM will trigger the check engine light.

 

[group captain mandrake]

Also, if your exhaust is smelling rich, I would be concerned. The ECM should set the check engine light long before you smell a rich exhaust-at that point it should be a flashing light.
If you can smell a rich exhaust, you may have been running rich enough to allow enough unburned fuel to reach the catalytic converters to turn them into blocks of charcoal. Obviously that would be a very bad thing.
I replace pre-cat O2 sensors every 60k miles, unless they fail sooner.

 

[Discoinjapan]

All I can say is, my highway mileage improved drastically after swapping mine out.

Mike

 

[flyfisher11]

Yes! At 80k I changed mine and I got an increase.

 

[brian4d]

getting colder in the midwest too so your engine isnt running as efficiently, isnt that usually the case?

Last time I checked (ANY) engine loves cold weather, providing we're not talking about -20....

 

[Steph]

Hoped to improve mileage after changing all 4 O2 at 58000 miles.

Wasn't throwing codes and absolutely no improvement in m.p.g.

So, I wouldn't change them if you have no problems.

 

[MonLand]

Sven is right. But you need a quick-reacting (scoping) scanner or, preferably, an ocilliscope to observe the signal switching frequency from the O2 sensors (and it helps if you know what to look for).

What frequency should we be looking for the switching?
I think the ECU also checks for that frequency and will throw a code for "slow" sensors. At least, I think that's part of the OBD2 specs.

 

[adriatic04]

Last time I checked (ANY) engine loves cold weather, providing we're not talking about -20....

the engine likes cold air to keep from overheating but cold weather will decrease MPG. engine load, cold starting, air, all are contributors to this. more fuel is used during cold starting to get the engine to optimum temp, so with cold weather hitting your engine ecu is sending more fuel to engine to get it to temp quicker. also, other fluids, like oil contribute to more engine load during warm up, which attributes back to the engine taking longer to reach optimum temp.

now once the engine is running at peak temp, cold air is nice, because it helps regulate that temp compared to hot air.

 

[BackInA88]

Thanks a lot guys.
My scanner does not give me live data just whether the O2's are OK or not. I have no codes what so ever.
The engine is running great just down on mileage about 2 to 3 MPG.
No power loss or rough running.
No air leaks I can find, using the carb clearer trick.
Air filter only a month or so old, seen only paved road since installed.
Trucks still coasts fine up to stops, so nothing seems to be dragging.
I drive 20 miles one way to work, couple miles being secondary roads and the rest being 70 MPH highway.

I don't remember a mileage decrease last winter.
We have only been getting down into the high 40's until the night before last when it was 37.
So unless my regular gas stations (BP or Mobil) switched to 10% alcohol, which I understand they are not required to post anymore?
That could explain it.

So I may just go ahead and replace the front O2's since they have over a 100K on them.
Who's got the best deal on new front O2's?
Rather have "plug and play" than have to splice universals in put I will if the price is right.

Steve

 

[MonLand]

Who's got the best deal on new front O2's?
Rather have "plug and play" than have to splice universals in put I will if the price is right.

Best price I've seen so far was on splice universal sensors on eBay (can't remember the name of the store)

 

[jeffro0502]

I just replaced mine with Bosch sensors from Autozone I think they were $69 each. I was happy with the result. I was getting the codes and mileage suffered a bit.

 

[Butch]

These are from Summit Racing (for a D1) $63.69

http://store.summitracing.com/partdetail.asp?autofilter=1&part=NGK-25044&N=700+115&autoview=sku