So far we've had 2 members (that I remember) who have said the factory average fuel consumption gauge is reading pessimistic:

Polkiuj...

Quote Originally Posted by Polkiuj View Post
Interestingly the mirage gauge is not optimistic but pessimistic! I constantly get about 5-6% more than what it reads.

It varies up to almost 9% at times!

The only time it actually read less was when I fueled up with petronas but the difference was only 1% less.

You can check my fuel log. It has almost complete data.
From: Speed vs. mileage/fuel economy chart - Mirage 1.2L 5-spd

CLARK ...

Quote Originally Posted by CLARK View Post
The economy I'm achieving is better than indicated on the instrument panel by up to 2km/ltr. - a pleasant surprise.
From: First impressions (Mirage GLS CVT)

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Has anyone else been comparing their gauge to actual calculations of fuel volume at the gas pump vs. distance?

I think it would be unusual for the gauge to be pessimistic - usually people who check these things complain their cars' fuel economy gauges tell a story that's too good to be true.