Opel CDTi (badge, not an engine)

CDTi is a badge, not an engine, and on an Opel or Vauxhall it is the least informative name in this catalogue — because the engines under it were bought from three different companies.

Our own rows show it spanning 1.3 to 3.0 litres, and the codes tell the story: Z17DTL is Isuzu's, DV6 is PSA's, Z19DT is Fiat's JTD, and A20DTH is General Motors' own. Four suppliers, one badge, on cars sold side by side.

So "my Vauxhall CDTi" identifies nothing, and the useful literature for one of these may be Italian, French, Japanese or American. Establish the code — it is on the engine and in the service record — and the right source follows immediately.

Two of those engines have pages here already and their faults are theirs rather than the badge's: the DV6 is the PSA 1.6 with its well-known turbo oil-feed screen, and the 1.3 Z13DT is Fiat's Small Diesel with its swirl-flap manifold.

The one thing the badge reliably means is a common-rail turbodiesel, and the ordinary consequences follow — DPF and EGR both suffer on short journeys, and on these cars particularly the EGR cooler is a recurring item.