Steve Campbell replied:

I would suggest that rather than additives which mask the problem, you go to a good deisel tech and get the problem solved. Black smoke is unburnt fuel, and the two biggest causes are injectors(by far the biggest cause) and injector pump out of adjustment. Get you injectors checked first...and your motor should have a new lease of life.

Ken replied:

I agree with the above comments but also be aware that the RD28 motor in GU patrol is an efi with electronic controlled injector pump 'fly by wire' throttle and many sensors and senders on the engine, an engine management diagnostic may also be required. Regards Ken.

Rex replied:

Carefull you are not using chep diesel fuel.

The no namers are using imported fuel and produces less power, burns more fuel and smokes like a wet fire !. Diesel fuel seems to vary a lot, even amongst name brands

mark replied:

Jim,I hate to say it but I reckon your problem has been self inflicted.If you have been using fuel additives you have probably disintegrated the gasket in your diesel pump , reducing its pumping pressure and the efficiency of the injectors.Chem Tech is a very strong solvent which dissolves resins etc from injectors but also attacks rubber seals. check the top plate of your diesel pump for any dampness. rectify this and change filters regularly and use good quality brand name fuels and your smoking problem will improve.