I'm not too sure about this as I've had a letter back from DVLA giving me specific instructions on how to change fuel category and then claim the "alternative fuel" taxation rate -- I've done a quick hint file (.doc) about this but can't attach it here. It's not intuitive -- it entails reading many obscure pages on their web site -- of course that's not by design
Since that February letter, on 26th June I had a rebate against a year's tax paid of £325 of a whole £9.17p. And a fresh V5C now showing Type of Fuel as GAS BI-FUEL. But although I forwarded the LPG Conversion Certificate to prove conversion that shows LPG after Conversion CO
2 of 8.1 and Hydrocarbons of 1.07 (no units shown though), the emissions' listing on my new V5C has remained the same as it was for petrol -- CO, HC, NOx, and HC+NOx. So I'm still going to be discriminated against under TfL's or the pretentiously-named "Mayor's Office" uLEZ rules that don't allow me access to the congestion charge zone unless I cough up £12.50 -- the meaning of which is clear: those that can afford to cough up £12.50 for every visit are not polluters. I tried to raise these points with the "Mayor's Office" / TfL but still have had no reply.,
But it gets worse. It's already been shown that the basis of euro pollution monitoring and enforcement rules is scientifically wrong. It's diesel particulates that are the worst offenders. Petrol engines are not measured for particulates -- my V5C has no entry in that box
So, apart from the welcome small incentive from DVLA for owners of older vehicles converted to LPG, TfL / Mayor's Office are still enforcing old outdated euro-regs that do not (because DVLA does not update V5C information) recognise LPG's more clean-burning characteristics.
And those living and working in city centres are still subject to carcnogenic diesel particulates when the righteous left are going around claiming to be our saviours
Luckily there's only a few more months of this euro-inspired madness to endure
(it says here March 29th -- is that right? Ed). Unless we've signed up to regulation harmonisation in this regard too without actually taking a look at what we're signing up to
Thought it might be useful to try and be constructive and post how I managed to get DVLA to change my V5C and give me a rebate: Applications for change of Taxation Class can only be made at payment of vehicle tax (with a V10 so I didn't apply until May coz I was SORN what with all my steering column lock problems); or if vehicle is already taxed (on a V70). The new category to be entered on either form is BI-FUEL TC59. Proof of conversion and the old V5C should be included.