7-day Test - GS450h vs GS430 comparison

Models tested: Lexus GS450h/GS430
RRP: $121,990/$137,200
Price as tested: $121,990/$137,200
Road tester: David Dowsey
Date tested: July, August 2006
Distance covered: 1342km/382km

Forget conscience -- the one thing separating the Lexus GS450h and GS430 is money. It's hybrid economy versus V8 grunt wrapped up in the same package. Both offer good looks, pace and luxury, the difference is that according to Lexus the GS450h offers "guilt free performance" while the GS430, err, does not.

From almost any angle inside and out the GS450h and GS430 look the same. Save for different instruments, the only difference you can see lies under the hood -- and in the boot.

The GS450h boasts a 3.5-litre V6 engine and two electric motors to motivate it. The electric motors are used for starting, idling and gentle driving -- the V6 comes into play to charge the electric motors and when more power is required.

The hybrid 'cycle' is deceptively simple. The petrol engine and braking forces charge the electric motor's battery -- located in the boot -- while the electric motor saves fuel while the petrol engine is taking a break.

The electric motors and the V6 engine between them provide a total power output of 254kW and 368Nm so performance is pretty brisk -- Lexus claims the 450h can sprint from 0-100km/h in 5.9secs. That appears a bit optimistic, but even so a time in the mid-sixes would still be very impressive.

There is a catch though. To run the electric motors the car requires a massive battery. And the battery and other hybrid components weigh 250kg pushing the car's weight up to 1865kg. This blunts both handling and fuel economy.

Lexus claims the 450h has 31 per cent better fuel economy than the V8-engined GS430. But that's not what we discovered. Deliberately driven as economically as possible we were disappointed with the overall average of 8.9lt/100km.

Confusing the matter somewhat is that while the hybrid doesn't quite deliver on its petrol miser promises the 430 over-achieves in the fuel economy stakes. We found the 208kW/417Nm 4.3-litre GS430 delivered 9.9lt/100km which is excellent for a car of its type and rather makes a mockery of the one litre difference the 450h delivers over 100km.

Both cars come equipped with the works including 10 airbags, satellite navigation, radar cruise control, adaptive headlights, keyless start and entry and rear parking camera. The leather swathed cabin is supremely comfortable -- though the low roofline means headroom is a little short of limousine comfort. So there's no difference there. The only variation is that the 430 boasts a cavernous boot that can swallow several golf bags while the 450h's is disappointingly small.

There's not much to separate the 450h and 430 -- unless you happen to play golf -- but for most it will come down to a question of dollars.

Customers shopping for a car in this price bracket won't be overly worried about the bottom line but when it's about the only difference between the two it's a no brainer.

The GS450h will save you $15,210 at the dealership, some cash with the tax man and $300-500 at the petrol pump per year. You do the maths. Just don't delude yourself that you'll save the world with the petrol savings.

Also read CarPoint's drive impressions of the Lexus GS450h here and Lexus GS430 here