Originally Posted by bushy
"Don't ever trust fuel guages" is a copout. They would not be fitted if they were no good.
Sorry Bushy, I disagree. The fuel gauges in most common GA types are shockers. They are
inaccurate. whatever else may be said float-type gauges as found in most of the GA fleet give every indication of having been supplied and fitted by the lowest contract bid.
The comments/reasons as to the possible excessive fuel burn have been excellent! Many many possible causes there. I would like to present another possibility:
The Lycoming engine as fitted to many C172's does have one interesting little feature that once very nearly claimed me... if the aircraft is being operated at or very near to full-throttle, as in an extended climb, the mixture is put into an '
auto-full-rich' setting, regardless of the pilots manipulation of the mixture control.
This is easily verifiable by an 172 drivers out there... simply climb to an appropriate level, set your cruise RPM and lean to peak, rich of peak or lean of peak, wherever it may be you operate your aircraft. Note the reading of your EGT gauge. Then simply slide full throttle in and watch what happens to your EGT.
It is possible to operate the engine at or close to full RPM without reaching the auto-full-rich, but you need first to know about it, before you know how to avoid it.
In an extended full-throttle climb, this alone can almost
double the flight-planned fuel burn.
Hope this is of some benefit.
Regards
RS