There are rumors that Tata is working on the diesel variant of there smallest car Tata Nano. Tata has been developing the Diesel engine for Tata Nano Diesel with Bosch which is a leading automobile component manufacturer. The diesel engine of Tata Nano will be even more fuel efficient with an estimated mileage of 40 Km per litre of diesel per litre of diesel, still the difference is quite higher or we should say more tha doubel as Petrol version of Tata Nano, which runs on a MPFI engine which is BS4 compatible and delivers 20+ KMPL of mileage.