What's this mean

[Chubba]

Noisy tappet sound at a cruise and decelerate but quiet at idle and under power. Is this a typical story for noisy tappets and would a tappet adjustment be the fix. 4.5L petrol/ LPG 254000 km

[dom14]

How did you know it's tappet noise, not something else?

[Chubba]

Don't. Just guessing

[nissannewby]

It is an easy thing to adjust the tappets so worth having a go. They arent really a hi tech engine so do have their noises.

[dom14]

Don't. Just guessing

Not sure it's tappets, following your description of the symptoms.
Anyhow, you can adjust the tappets with a feeler gauge and Patrol manual specifications.
Not sure whether the 4.5 engine comes with hydraulic lifters or tappets.
You will know when you open the rocker cover.