Car service from Lisbon to Porto

We used taxis quite often locally and occasionally for long distances.
On long distances we usually paid just over 1€ per kilometer, on a 200 kilometer ride we paid €240.
Between Lisbon and Porto would be over €300 .

You can take the AP train ( bullet train ) for about €40 per person in first class.
We also used the AP train often and enjoyed it, comfortable relaxed ride.

We used mydaytrip.com twice, Lisbon to coimbra with a stop in Obidos, and coimbra to Porto. We were a party of four to split the cost. Worked great.