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Diesel truck rookie

Question : I BOUGHT my first diesel pick-up, a Nissan Navara (A), last November.

1. Does having a Variable Nozzle Turbo (VNT) means the turbo is operating throughout the engine speed, unlike normal turbo which kicks in at a certain RPM range ?

VNT should give me better fuel consumption, but it's not up to my expectation. My latest record is 11.3L/100km at 85 per cent highway drive.

2. With a turbo diesel engine, can I shut off the engine immediately after long driving ?

Will it cause premature failure/high wear and tear on the turbo and engine due to oil cooking in turbo ? Do I need to install a turbo timer ? Will it void my warranty ?

3. I carry back passengers more frequently than carrying cargo load. The load usually does not exceed 500kg.

Is it advisable to remove one leaf spring to reduce the stiffness and increase comfort for the passengers ?

4. After an hour's drive on the highway, there's always a squeaking sound (according to road undulation) which I strongly believe comes from rear springs.

Is it advisable to lubricate the leaf springs with engine oils ?

5. On my first 1,000km service, valve cleaning and engine oil flushing is required.

Is this necessary ? From the service dealers' explanation, I get the impression diesel engines are so delicate and need more care than petrol engines.

Answer :

1. A Variable Nozzle Turbo gives better performance over a wider engine speed range compared with a "normal" turbo that has a tendency to give its best performance at higher engine speeds.

Regarding your fuel consumption, I cannot really comment as fuel consumption depends on many factors, including your right foot. Maybe you should try changing your driving style to see if it improves.

2. Usually with turbo engines, it is recommended to allow the engine to idle for a short while after stopping to allow the turbine in the turbo to slow down.

Switching off the engine immediately after revving the engine can cause the turbo to spin down with insufficient lubrication.

Turbo timers force the engine to idle for a set period but it is best to check with your vehicle distributor whether it will void your warranty.

3. Some people have removed one leaf to soften the suspension but remember that by doing this, you are reducing the load carrying capacity of that axle and you cannot carry the designed load after the removal.

4. You can use a small quantity of engine oil to lubricate the leaves where they are touching and not soak the whole spring set in oil.

You can lever the leaves apart with a large screwdriver with the body jacked up and using an oil can to squirt the oil between he leaves.

5. Is that a recommendation of the manufacturer or the service dealer ?

I have never seen any document from a manufacturer suggesting such work to be done at the first service.

If it is the dealer's suggestion, i think you should find another service workshop.


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