Hi All,
I've had a niggling feeling for a while that my fuel economy isn't quite what it should be. Not bad, but then again not good.
E.G. I'm getting low to mid 30s on a motorway run ( 2.2 Petrol auto ).
I think I see the reason here

As you can see the o2 sensor voltage is consistently too low. It should vary around the 0.45V rather then 0.1.
The data was taken using the logging facility on torque pro ( android ) for a short journey on a duel carriageway.
There are no ECU faults stored or pending.
Great I think. I'm running lean, just need to find that pesky vacuum leak, and it will all be sorted.
My problem is, I just can't find any leaks.
I've tried butane and carb cleaner, and even water to isolate the leak.
I swapped over the o2 sensor with a known working one from another car - Just in case. There was no change.
Here is my long term fuel trim.

So where do I look now? Is there a common place the vacuum system leaks? Or perhaps something else.
Thanks
Rob