I've been toying with swapping my petrol lump for a 200TDi but if I assume the petrol does 18 to 20 mpg and the diesel will do around 26mpg (I know people say 30 but realistically with an old TDi it's going to be lower) then I save about 3.8p per mile at the current diesel/petrol prices.
So if I spnd £1K on the swap it takes over 26,000 miles to pay back; at £1.5K it takes 40,000 miles. As these swaps always work out more expensive than estimated, it's gonna be near £1K or a bit more. As my mileage is less than 10,000 pa I'm thinking about keeping the cash in the bank and running the petrol motor as it is a nice smooth engine, it's less hassle and it's really cheap and easy to work on.
I'm then going to upgrade to a newer LR (prob 90) in about 4 years when my circumstances change and I can use it as my main motor.
I appreciate the TDi is more powerful/nicer but if you're looking at running it with no turbo or a n/a diesel, I don't think it's worth swapping it - especially in economy terms. A nicely tuned 2.5L petrol engine is not great, but is fine and motors along with traffic fine, and I've towed some pretty heavy stuff with this motor with little problem.:clap2: