I think it might be knocking more than normal, this is the only diesel I've had experience of, but it does seem noisy. Like you can hear every explosion in a pinking sort of way but louder. Might be only a quarter of them but it's hard to count.

It's always been like this since I bought it and I just thought that's what they sound like. We've put 40000 on it and it runs great. I think I shall have to measure the mpg and judge it from that. Replacing a leaky injector or taking it to a diesel specialist for testing sounds a lot more expensive than more frequent oil changes.

I did put some diesel redex in a while back that I had no further use for, in a spirit of optimism, so I'll stick the rest in and see if that helps.

Thanks for your advice Peter N