Actually I just filled up my 3.2 and after doing 100 miles of motorway (sensibly) and 185 miles of ragging it about York I averaged 22mpg, using 97 RON fuel. Not too bad! How you got 18mpg out of a 2.5 I don't know!!
Quality motor but you want a newer and better cared for example
I average around 25mpg on short trips (6 miles) back and forward to work but regularly acheive 30mpg (even 35mpg on occassion) when I go on a run. I took the Super to France on holiday this year covering 2500 miles on varying roads at varying speeds (85mph [cruise on] on French motorways, M25 dead stop for 2 hours but engine running, blating about french rural roads) with a fully loaded car and got 28mpg overall for the trip!
As long as a 166 is cared for the ongoing maintenance will be bearable BUT problem is that due to bargain basement prices now, some are not receiving the care they should and a lot out there are full of problems which will cost a lot to sort out. BUYER BEWARE!
Gone but not forgotten - 164 3.0 12v - 156 1.8 SP1 - 164 3.0 24v - 156 SW 1.8 SP3 - 166 Super - 166 3.2 Ti - Brera SV JTDM - 156GTA - 147GTA - 147GTA - 156GTA - currently Alfaless
All belts and tensioners will need to be changed - No question about it, do not live on the edge!! Rubber components have a fairly short life span. Only 19000 miles in 6 or 7 years could bring other problems also - I would check out rubber fuel pipes for leaks or deterioration, the brakes, all the bushes and electrics.
The Super does not have a metal impellor - The 3.0 GTV does and is a common upgrade on the 166 but not fitted by Alfa as standard!
To be fair there reliable cars, you'll prob need to change the radiator soon and maybe the water pump while your doing that! MAF may also need a clean in the next 30k (easy job), side lights..........ask me how to correct the xenons (you'll know what i mean when you cross that bridge).