Nissan Navara Problems

No it's not normal for a modern diesel to blow a lot of smoke. It sounds like it's too rich, check the fuel pump.

I'd be inclined to take the advice of your mechanic, but if you are still concerned get the opinion of another mechanic. It should be easy, simply by listening to it, to determine where the noise is coming from, and from that whether it is a timing chain or not.

I have had the odd reports of timing chains breaking, but every time I have checked into the issue I have been told the main reason for the failure is either a lack if servicing or poor servicing. It would appear that Nissan engines are more sensitive than most to having fresh oil running through their galleries and regular oil changes should be carried out religiously to avoid a build up of sludge resulting in blocked oil passages.

80 litres is the volume of the tank, but that’s allowing for expansion of the fuel as the temperature rises, so you will never get the full 80 litres into it. The 70 litres you’re able to get in is about right.

Check the injectors, your problems are most likely there.

I could imagine that you could get better fuel economy when the cruise is not engaged, but it would depend on the calibration of the cruise and how aggressive it is, the specific vehicle in question, and the way you drive normally when the cruise is not in use. I doubt you could draw a general conclusion that fuel economy is always better when you don't use cruise. Perhaps you should try it for yourself and see if it does work for you.

There are reports of engines failing, but those that have appear to have failed because they weren't serviced by the book. It's important to religiously service the Navara, and use the Nissan recommended oil. The failures we have heard about are mostly failures of the camshaft, cam timing gear etc that have led to more serious damage. It's believed the initial failure of the cam or cam gear is due to a lack of proper servicing, leading to blockages in the oil passages feeding the top of the motor.

My contacts say there is no problem with the chain on the D40, bearing in mind that all chains will stretch over time, so you have to suspect the service guy is trying to sell you something you don’t need. On top of that there should be no difference between the Spanish sourced model and the one from Thailand, as the engine is the same in both.

Have you checked your invoice to see how much oil you have been charged for? It could be a case of being overcharged for oil you don't need, or it could equally be incompetent service staff simply overfilling your engine.