In this article, dated 13th September 1928, Anderson clearly states he named the Bristol aircraft (not just the engine), the "Old Pioneer" due to her "past achievements".
Aviation News - Sept 1928
CAMOOWEAL, September 10.
MR. KEITH ANDERSON, in company with Mr. Hitchcock, who are endeavouring to fly to London in 14 days, advises:
"We were favoured with clear skies and little, if any, wind, on our journey for Longreach, arriving here at 4.30 p.m.
Everything is OK with the Old Pioneer, which name I have given the 'bus on account of her past achievements.
Both Mr. Hitchcock and myself are very pleased with the performance of the machine and engine, and are confident, given reasonable weather, we will make London in under 15 days' actual time from Sydney.
Tomorrow we will start on a non-stop journey from Camooweal to Darwin.
Our long hops subsequently will increase our daily average substantially. To-day has been hot, the thermometer registering 95 degrees here.
The country around Longreach and Winton is parched. We hope to make tomorrow's despatch from Darwin interesting."