It's been a tale of two very different cars for Ford at the LA Auto Show, though both have one thing in common: economy. The all-new US version of the Ford Fiesta joined the updated Mustang - with its 3.7-litre V6 - to show both sides of Henry's American operation at its best.

Ford has launched the Fiesta in the US with a 1.6-litre petrol engine capable of 40.0mpg combined economy, placing it well ahead of the average fuel consumption for cars in North America. As well as the five-door Fiesta we're used to in the UK, Ford revealed a four-door saloon for the US market at the LA show.

The 118bhp 1.6-litre engine comes with a five-speed manual gearbox as standard, but for auto-loving US buyers Ford will offer the new Powershift six-speed, dual-clutch auto 'box. This DSG-style auto is similar to ones already used in some European Ford models and there are strong indications this transmission will be offered to European Fiesta customers in the near future.

Other new technology for the US-spec Fiesta includes a driver's knee airbag and AdvanceTrac with ESC electronic stability control. Chief engineer for the US version of the Fiesta, Steve Pintar, said: "The global Fiesta was tweaked for North America, not redesigned or redeveloped. We're proud of how little has changed from the European model." However, the US-spec Fiesta only shares around 60 percent of its components with the European model, and even less with the saloon.

The Fiesta goes on sale in the US in January and there are said to be 15,000 customers waiting to buy the car. Prices have yet to be announced, but a Ford source told us the car would start at less than $15,000, which is equivalent to about £9,000.

Also on Ford's stand in LA was the new 3.7-litre, V6-engined Mustang. It may be the little brother of the fast Ford coupé range, but the new V6 engine packs 305bhp to have more power than the first of the current generation's V8-powered models.

The V6 is also a step in the right direction for economy as it returns an average of 30.0mpg. Variable cam timing is used to make the engine efficient and powerful at the same time, though the headline economy figure is for the six-speed automatic gearbox, while a six-speed manual will also be offered with the car.

The new engine revs to 7,000rpm and with 305bhp on tap Ford has upgraded the chassis of the Mustang to cope. A limited slip differential is standard, along with larger brakes and revised spring and damper settings. A Performance Pack will be available from August that comes with 19-inch alloy wheels, revised axle ratio for better acceleration, ESP with Sport mode and a front strut brace to stiffen the body for better handling.

The new 3.7-litre V6 Mustang goes on sale in the spring of 2010 and Ford says it will confirm prices closer to that time.

Alisdair Suttie - 2 Dec 2009