Gas on test
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• British Gas presented a range of vehicles from a vee-six Ford Granada to an Iveco Ford Cargo with a dual-fuel engine which operates simultaneously on diesel and CNG.
CM drove a 2.0-litre Transit with a £1,300 conversion which can be manually switched between CNG and petrol. It uses spark ignition in both modes, and automatically reverts to petrol when gas pressure is low.
Performance was down when running on gas, particularly at high revs, though the engine became noticeably quieter. We also drove a Leyland Daf Roadrunner with a 5.9-litre Cummins B-series converted in 1992 to run solely on natural gas. With its compression ratio reduced to 12:1, and motorcycle spark plugs for ignition, the engine revved freely and felt much livelier than a diesel, but lacked low-end torque. Noise was much reduced with none of the usual diesel clatter at idle.