Most A/c get around 10-15% better TAS in Aus over Winter compared to Summer!
In something like the 210 that's a difference of around 20 knots or more and in 35 years of flying I've never ever seen a discrepancy that big whilst in the cruise regardless of what the temp is.
Someone might be able to work the numbers in the pics to give us a TAS for the 210.
IAS 150kt, 9,500', QNH 1025, OAT 26°f.
IAS 152kt, 8,500', QNH 1026, OAT 35°f.
Have to say though, I was cheating. It
was a cool day and I had a big load. Me, Mrs.GB (All 54kgs of it), fuel and bags. From the nanny state to Broome in 9 hours. Not to shabby.
Apologies for the thread drift.