Having asked at an ATF yesterday about this, it seems to be a bit hit and miss what happens. The revision record for the testers manual appears to indicate that for pre 1/7/2008 vehicles the data on the manufacturers plate should be ignored. This appearing on page one of the 2018 on-line HGV inspection manual as a revision dated 1/2/2019 which supersedes the 13/9/2018 revision instructions. There have been a variety of interprtations before this with many testers using this figure. Many other testers don’t bother to look at this part of the plate and the general consensus (off the record) seems to be to obliterate the figures for vehicles before 1/7/2008 so that the default values of 2.5 for N/A and 3 for turbocharged engines are used.
It looks very much like the date the vehicle was tested will govern pass or fail.
assets.publishing.service.gov.u … manual.pdf
This certainly needs clarification from DVSA Bristol. In particular if it is deemed that a vehicle tested in January of this year failed and it was then retested in February what are the OCRS implications?