Doyle's round got off to a shaky start as his drive at the 1st found the lip of a bunker and he could not get up and down to save par. He rebounded at the next hole when his 6-iron approach landed 12 feet from the hole to set up birdie.
He closed out the front nine with a pair of birdies, another from 12 feet at the 8th and a 30-footer at No. 9.
Doyle ran in three birdies over his last nine holes for his 67 and his seventh consecutive round in the 60s at Silverado.
'For whatever reason, this course suits my game,' Doyle said. 'It was definitely some odd conditions out there, but I like coming here. I've said that every year I've been here.'
Doyle is in a battle with Irwin and Bruce Fleisher for the Senior Tour's money title. He has won twice this season at the State Farm Classic and the elder circuit's final major, the Senior Players Championship.
'Probably no one else would have expected me to be in this position to win the title,' said Doyle, who used to caddy for Fleisher while he was on the PGA Tour. 'No matter what happens from here on out, I'd be very satisfied to win $2.6 million. I couldn't complain at all.'
Jenkins was flawless on Friday with four birdies and no bogeys. He made two putts from inside five feet at 11 and 14 and two-putted from 50 feet at the last to get to 4-under.
'I felt good about the round,' said Jenkins, who has won twice on the Senior Tour. 'This is a hard course when the wind blows and the greens get hard.'
Irwin, seeking his fourth win of the season, picked up three birdies on the front side but dropped a shot at the 12th when his second shot found a greenside bunker. He made back-to-back birdies at 13 and 14 but bogeyed the 16th.
Irwin two-putted from 20 feet at the par-5 18th to join Jenkins in a tie for second.
'I'm just trying to get through the year,' Irwin said. 'The old body is breaking down. Considering how I felt and the conditions, I'm very satisfied with that score.'
Terry Mauney, Rocky Thompson and Don Pooley share fourth place at 3-under par.
NBC commentator Roger Maltbie made his Senior Tour debut and it was one that he would like to forget. He posted a 7-over 79 that included a double- bogey and a triple-bogey.