If you want the stingiest second-hand sippers in Australia, hybrids run the show.
Top picks: Toyota Prius (~3.4–4.4 L/100 km), Corolla Hybrid (~4.2–4.5), Prius c (~3.9–4.1), Camry Hybrid (~4.2–5.2), and Hyundai Ioniq Hybrid (~3.4–3.9).
On the cheap-and-cheerful petrol side, a Mitsubishi Mirage, Mazda 2 Skyactiv or Suzuki Swift can manage roughly 4.6–5.5 L/100 km if you drive like fuel costs money (because it does).
Diesel hatches like a Golf TDI sip on the highway, but city short trips plus DPFs can turn savings into swear words.
Real-world figures depend on tyres, servicing and your right foot, so buy on condition and history, not just brochure bragging.
Consult official documentation for exact figures.