My 2004 Honda Jazz was becoming sluggish. It had done 220,000 km (137,000 miles).
I live in hilly country (Greece) and the car was reluctant to climb some hills even in 2nd gear. Also the fuel consumption had gone up to 6.3 litres/100 km (45 UK mpg) and, when crawling in traffic, the car had started to "kangaroo" hop.
I used to do all my own servicing but, at age 73, I'm not as keen or supple as I was, so I entrusted the refurbishment to a trusted mechanic.
So, for the record, he replaced all of the valves and piston rings. He had the hydraulic tappets and fuel injectors professionally cleaned. New seals, gaskets, filters and synthetic engine oil completed the job. The new piston rings were made in the USA. The engine did not need a rebore - just a light cross-hatch hone - or new pistons. Amazing.
Now the engine is quiet and more lively. Fuel consumption has dropped to 5.9 litres/100km. (48 UK mpg)
Total cost including full annual service, parts and labour was 1,400 Euros. I could have got it done cheaper but, as I said, I trust this mechanic.
I hope this info. helps someone.