THE optional supercharged V6 engine available in the Commodore S utilises long-term experience gained in front-drive Buicks in the US. The engine has over-square bore/stroke dimensions of 97mm by 86mm, displaces 3.791 litres and is essentially the same as the regular cast-iron, overhead valve V6 but runs a lower 8.5:1 compression ratio (9.4:1 in the regular 152kW V6). It uses cross flow cylinder heads, while low friction technology was adopted with a major overhaul in 1995. It also has "hot wire" air mass metering, sequential fuel injection, twin knock control sensors, computer diagnostics and high energy distributorless ignition with three separate ignition coils, each one looking after two cylinders. The supercharged engine produces 171kW at the same 5200rpm as the standard V6, and bumps torque from 305Nm at 3600rpm to 375Nm at a lower 3000rpm. Holden recommends premium unleaded fuel but says it is okay to use regular unleaded, although it will not produce the same power figures. A full stainless steel exhaust system has a longer life expectancy than a regular steel system. The supercharged engine is only available with an automatic transmission, running the same ratios as the regular V6.