Ryan Hunter-Reay put Andretti Autosport at the top of the timesheets following the 45-minute Saturday morning practice session ahead of this weekend's GoPro Grand Prix of Sonoma, the season finale of the 2015 Verizon IndyCar Series.

Hunter-Reay's best lap came in his very first effort and clocked in at 1:16.8702s (111.695mph) on the 2.385-mile, 12-turn road course, already far outstripping the existing track qualifying record of 1:17.2393s (111.161mph) set by Penske's Will Power last year on his way to pole position and clinching the 2014 title.

CLICK: Full Saturday morning practice 2 times from Sonoma Raceway

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In fact the top ten drivers were all under Power's qualifying record time. Coming in just 0.0287s behind Hunter-Reay in the session was Rahal Letterman Lanigan Racing's Graham Rahal. Josef Newgarden (CFH Racing) was third fastest while championship points leader Juan Pablo Montoya was fourth, still within six hundredths of a second of Hunter-Reay's time.

Montoya - who has been out on front in the championship since winning the season opener at St Petersburg in March - currently has a 34 point lead over Rahal in the title race. As well as Newgarden, the other drivers still mathematically in with a chance of snatching the title away from Montoya are Ganassi's Scott Dixon (fifth fastest on Saturday), Penske's Helio Castroneves (sixth) and Will Power (ninth). Power is a three-time winner at Sonoma Raceway and has started from the pole four times in the past five years.

Other drivers beating the 2014 pole record were Andretti Autosport's Carlos Munoz (seventh) and Ganassi's Tony Kanaan (eighth), with the top ten rounded out by the remaining Penske driver Simon Pagenaud.

Drivers were helped to their flying lap times by new primary and alternate Firestone Racing tyres being used for the first time this weekend, which feature softer compounds to improve grip levels around the circuit.

Just missing out on both the top ten and pipping the 2014 qualifying record was Sebastian Saavedra, who was 11th fastest in the session as he returned to the race seat of the Ganassi #8 in place of Sage Karam with whom he has been sharing the car this season. Meanwhile Mikhail Aleshin had an impressive run to 13th place in the Schmidt Peterson Motorsport #77 after a year away from IndyCar.

There was a good showing for the Dale Coyne Racing cars, with Rodolfo Gonzalez ending up 21st on the timesheets just a tenth ahead of his team mate Tristan Vautier.

Returning to the IndyCar Series for the first time since Indianapolis, Oriol Servia was 24th fastest in the Andretti Autosport #25 that he is driving this week in tribute to his friend Justin Wilson, who was tragically killed after sustaining severe head trauma in a freak accident at Pocono last week.

The slowest of the 25 drivers taking part in the session was SPM's James Jakes, who was 1.7585s off Hunter-Reay's pace but still enjoying his time back at one of his favourite venues.

"Sonoma is a great place to end the season. It's one of my favourite tracks on the calendar," he said. "I really like the layout because it's very challenging and feels great when you can put a lap together. With so many different types of corners, it's always a challenge to find the perfect balance."

Thanks to cooler and more overcast conditions today, everyone ended up improving and going faster on Saturday morning than they had previously managed in the marathon three-and-a-half hour long session on the hot and sunny Friday afternoon.

See full Saturday morning practice 2 times from Sonoma Raceway