They are basically similar cars with different standard or optional equipment. Also available are electric mirrors and central power locking as optional extra. A three-speed manual transmission was standard with the automatic TorqueFlite optional. Headrests were now available as an optional extra. The new Explorer will be available with an optional trailer tow package. A six-speed manual is standard with a five-speed automatic optional. The architecture describes mandatory interfaces that must be available on all implementations, and optional interfaces. The mandatory TLVs are followed by any number of optional TLVs. L petrol engines, with the 1.8-litre four available with an optional turbocharger. The V8 engine was standard for Caprice models with the "Turbo Jet" V8 optional. Leather upholstery was standard on LTZ models and optional on LT models. TorqueFlite automatic also optional on V8 cars. The game is available as freeware with an optional pay what you want model. It was the only model available with the optional turbocharged flat-six. Oldsmobile's two-speed Jetaway automatic transmission optional.