I WRITE to reply to Stephen Reynolds's issues about the use of bio-diesel (July 26). Firstly his Ford manual may restrict the use of bio to five per cent mixtures but many modern diesel engines are more than happy to run on bio.

My Skoda manual specifically allows 100 per cent bio.

I agree that "straight vegetable oil (SVO)" is not suitable for most diesel engines. However Otto Diesel's engines ran on peanut oil and the problems are due to SVOs' greater viscosity and higher gel point necessitating heated fuel tanks and lines rather than any fundamental incompatibility.

The solvent capability of bio is well documented and use in an older diesel engine can result in the loosening of accumulated "gunk" perhaps requiring the fuel filter to be cleaned. It is older engines using rubber seals that have problems.

Winter usage is not a problem - winterising agents are readily available and if we keep burning fossil fuels cold winters won't be a problem anyway.

Even an electric car emits carbon dioxide at the power station - at least bio is "carbon neutral" and the particulates are apparently less carcinogenic that those from petro-diesel. Mr Reynolds also omitted to point out that bio is sulphur free.

While not perfect, bio could make an easy contribution to reducing our emissions of fossil carbon and also provide an alternative source of income for farmers. See www.biodieselfillingstations.co.uk for more information with a UK rather than US perspective.

How about a "green" car - a hybrid electric-diesel with the diesel engine running on SVO?

D J Mitchell

Main Street,

Alne,

Easingwold.

Updated: 08:44 Saturday, July 30, 2005