STUART Taylor painted a very rosy but I'm afraid misleading picture of bio-diesel ("Motorist Hails Bio-Diesel Car", July 18).

The Ford owners handbook states, "Do Not Use RME (Bio-Diesel) except in the case of these proprietary diesel fuels which contain a mix of up to 5%. Ford can accept no responsibility for damage caused by using RME (bio-diesel) in concentrations greater than 5%."

The handbook goes on to warn: "Do not use vegetable oil instead of diesel. Ford can accept no responsibility for damage caused by using vegetable oil at any concentration."

Other manufacturers have their own warnings and recommendations.

The Utah Bio-Diesel Co-Operative reports that bio-diesel's solvent properties cause fuel line problems, releasing accumulated deposits and blocking fuel lines and filters causing engine hesitation, misfires, sluggish performance and vehicle breakdown.

In winter bio diesel suffers another disadvantage due to its potential to gel. Older vehicles made before 1993 with nitrate rubber used in the fuel lines, have an even greater propensity to failure.

Bio-diesel fuelled engines, like their regular fuel counterparts, still emit carbon monoxide, unburned hydrocarbons, carbon dioxide and particulate matter. Bio-diesel also has a lower BTU (British Thermal Unit) than regular diesel causing a decrease in power and decrease in miles per gallon.

Bio-diesel may well be renewable but it's not the future.

Stephen Reynolds,

Selby Ford,

Canal Road,

Selby.

Updated: 10:37 Tuesday, July 26, 2005