I am assured by a reputable trade supplier that Bosch Super plus yttrium WR9D+ spark plugs are correct for my 2000 4.0 Range Rover. The web site carsparkplugs.com also throws these up amongst others for the "99-02 Range Rover 2", but their cross reference to the Champion RC11PYPB4 (type shown in owners manual) is a Denso KJ16CRL11 with a gap of
1.1mm. The recommended gap in the owners manual is 0.95-1.05mm. The Bosch ones are 0.8mm! Why this difference in spec? Is this a deliberate ploy to confuse the consumer? Should I stick rigidly to the Champion RC11PYPB4?I have a drop in power and rough running under 2000rpm. I have replaced the leads and the problem is improved but still not as it should be so I suspect plugs.
Any advice on the plugs to use (or not to use) on this engine appreciated.
David.