TN A300s
The TN A300s were B4 models. The poor fuel economy was due to being CF6-50 engines. The CF6-80 was on the B767-300, hence the better fuel economy from that aircraft model. However the CF6-50 was more fuel efficient than the B767-200 JT9 powered aircraft. The reason they were good for freight was they had the full width holds enabling two LD3s side by side. You couldn't do that with the B767.