Fernando Alonso is braced for the "most horrible" laps of his racing career during qualifying for the Indianapolis 500 this weekend following advice from his mentor, Gil de Ferran.

De Ferran won the Indy 500 in 2003 and is acting as Alonso's coach throughout his preparation for his maiden race outing on the Indianapolis Motor Speedway oval next weekend.

Two-time Formula 1 world champion Alonso has been getting to grips with his McLaren-Honda-Andretti Dallara DW12 car this week in practice, finishing fourth-fastest on both Wednesday and Thursday.

"The car felt quite OK from the very beginning in the morning, but then I think we did improve it during the day. I'm quite happy," Alonso said on Thursday.

"We're working still a lot on the race simulation, meeting other guys out there and running in traffic, and I think we've found a good balance for traffic. I think tomorrow we will concentrate a little bit more on qualifying, but priority is the race."

Alonso's focus on perfecting his qualifying setup comes following advice from de Ferran about the four-lap run that requires drivers to be on the limit throughout or risk falling down the grid.

"We've still full concentration on the race situation, so I think tomorrow they will for sure help me in a way to understand what we need to be quick in qualifying, what's the key point on the laps, on the qualy," Alonso said.

"So far, Gil de Ferran, my coach and mentor, told me that the four laps in qualifying will be the most horrible laps you've ever done, because the car is very on the limit.

"I will have a first touch tomorrow on Fast Friday and then we'll see on Saturday."