I recently bought a 1975 C182P. It has a zero timed engine with only 190 hours on it. It runs great and seems to have loads of power for what it is. I found another thread on fuel burn for the 182: http://www.pilotsofamerica.com/forum/showthread.php?t=61014 which was helpful and interesting but did not quite answer my questions. I have been monitoring my fuel burn fairly closely. I'm doing a lot of touch and goes, climbing and descending and short flights so I would assume my burn would be a bit higher, but found that I am consistently burning 10.5 to 11.5 GPH. That is all fine, but I am really confused about speed/performance. My plane seems to be flying very slow compared to the speed I should be flying based on the cruise performance chart. I have tried flying at various altitudes and numerous MP and RPM combinations but it seems that basically no what I do, the plane will not fly over 115 knts (this is all for carefully trimmed level flight in smooth air). I have typically tried to fly at various MP/RPM settings which would give me around 60% HP, which should give me approximately 130kts. These settings along with my recorded fuel burn fall right in line to give me the 130kts in the charts, but my plane just cruises at 110 and will not go over about 115kts in smooth and level flight. I thought possibly the IAS was incorrect, but I have checked it against my foreflight speed (then calculating for a tail/head or cross wind) and IAS and foreflight are nearly exactly the same. Always getting the 110kts on IAS and about the same on foreflight. I have made sure my cowls are closed (which seem to affect speed by maybe 2 or 3kts), that I'm trimmed properly, numerous experiments with EGT (which I normally set to about 50ROP), etc. etc. My thoughts on what is going on (because I do think my airspeed indicator is correct): 1. MP gauge is incorrect so I'm flying at a significantly lower MP that I think I am (a user on the forum I linked above wrote: "I was at 8500ft, wide open throttle at 21mp, 2300 rpm". When I am at that altitude and if I did the same settings, I would probably only be at half throttle) 2. Very old ADF/GPS and possibly a couple other antennas have been added over the years. This seems like very limited drag but could this be affecting speed? Given all my setting experiments (EGT, RPM, MP, trim, Cowl, etc) and average fuel burn of about 11, everything I'm doing supports IAS of 130kts, but I'm not getting that. Why????? Ideas, thoughts, etc. would be very most appreciated! Thank you!!!