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Discussion Starter · #1 · (Edited)
Hi,
I have just under 70k miles now, and I've been having 4 tanks of lower MPG.
Like, instant fuel usually hovered around 50MPG on the highway, now it's at 30-40, when doing 50-60MPH, no AC.

At first I thought it was my tires, since I recently changed a set. But I did the front 2 tires first, and didn't see a hit in MPG at all. Maybe 1 to 2 MPG most.
The tire pressure is above 32 on the rears, and above 35 on the front (cold), so it goes up to 38 front and 35 rear warm.

Then I thought I must have been getting worse gas.
I mean, the weather has been cold all the time, and only now we're experiencing 90+F again during the daytime.
It happens when the weather drops by 20 or 30 degrees in a few days, that I get supreme gas mileage.
And when it turns hot, I get lousy. But that's usually only one tank before it stabilizes.

So either Shell has lowered the quality of their gasoline,
Or, my O2 sensors are going bad.

Is there a possibility that O2 sensors are going bad at below 70k miles?
I did drive a fair amount of 80-85MPH highway driving, which pushes the engine quite a bit, and may have caused either fouling of the O2 sensors, or maybe the increased heat might have caused premature failure.
However the faster driving is not calculated in the MPG losses. At those speeds I have a mere 20MPG now.


If the O2 sensor is bad, is it a good idea to soak the tip in Hydrogen peroxide or a vinegar/H2O2 solution to dissolve impurities?
I don't know if it'll help, or if I really should be buying a new O2 sensor?

My car does occasionally hiccup at cold, idle RPM, but I didn't see any engine error codes.


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Gen 1, 2011 Cruze Eco, 1.4l turbo, 6spd automatic
 

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What is the change interval on them?
 

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Discussion Starter · #3 ·
From other sites, O2 sensors should last at least 100k miles, AFTER which they deteriorate.
Some still run on their stockers at 125-150k Miles.
 

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Discussion Starter · #4 ·
I figured it was the tires after all.
They're silicone based, and need higher pressure.
The stock Cruze tires did well between 30-37PSI. These do well between 35-45PSI.
The drop was due to the softer tire walls, reducing road noise, increasing grip, but also reducing MPG.
 
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