Surf Fuel economy

I'm thinking of updating from my petrol 86 4runner to a 3L Diesel Auto Surf. What's the economy like ks per litre?

I drive about 500-600 ks a week.

My 4y 2.2 petrol engine has 320,000 ks with one rebuild (ready for the next) and gets 8 ks per litre.

Thanks, Craig