Just had the light come on in my ST170, from Full to light on i got 219miles, that £50 of fuel. They are rubbish on economy. Im lucky and have a good one that is plenty quick enough. The VVT is constant, the valve timing on the inlet cam is constantly adjusted so you dont get the "switch over" of a V-tec its progressive. Its not the clutch that goes its the Dual Mass fly so the lot need swapping, i just did mine at 60K stuck at 12lb aluminium fly in and stage 3 kevlar clutch, expect to pay £500-600 for parts alone. The lightened fly has transformed the car. I know your not looking at modding it but mine has a filter, exhaust and re-map plus ported TB and lightened fly and it pulls hard right through the rev range. My brother in law has a new clio 197 and he can only pass me very slowly top end, i rape him in acceleration.