FORD Australia engineers are working on a mystery large car that is likely a replacement for its ageing Lincoln MKS for North America and China.

The test mule – based on a left-hand-drive American Ford Fusion but with major modifications under the rear end that appear suited to a larger vehicle – has been spotted by GoAuto going through its paces at Ford Australia’s busy You Yangs proving ground in Victoria.

As our pictures show, the disguised test vehicle has rear wheelarch extensions, seemingly to cater for a significantly wider rear track than the standard set-up for Fusion or its Mondeo sister model that is due Down Under in the second half of this year.

The EcoBoost V6 will likely carry over and be joined by Ford’s 2.0-litre EcoBoost four-cylinder, as used in the current Ford Falcon and many other Blue Oval models. Some journalists speculate these engines will be joined by a rumoured 2.9-litre EcoBoost V6 called Nano.

At some point, these engines are likely to be hooked up to a new nine-speed automatic transmission under joint development by Ford and GM.