Luis de la Fuente's side, with five European group stage victories so far, are poised to wrap up a spot in the finals when they meet Turkey in their last qualifier on Tuesday.
The European champions lead Group E by three points over Turkey, who also won their fixture on Saturday when they overcame Bulgaria 2-0.
Captain Hakan Calhanoglu put Turkey ahead in the 18th minute from the penalty spot after a handball.
The hosts doubled their lead in the 83rd minute when Bulgarian defender Chernev turned the ball into his own net attempting to clear a low cross.
The only way the Turks can pip Spain for the top spot and grab a direct ticket to the World Cup would be by winning in Seville by a huge margin.
Spain didn't appear to miss injured stars Lamine Yamal, Pedri Gonzalez or Rodri against the overmatched Georgia.
Real Sociedad striker Oyarzabal led Spain with his two goals and an assist. MartÃn Zubimendi and Ferran Torres also scored as their team was up 3-0 by halftime.
Oyarzabal opened the scoring with a penalty in the 11th minute and headed in the fourth goal in the 63rd. Marcos Llorente cleared a late Georgia shot from the goal-line to protect Spain's run of clean sheets.
Earlier, Belgium held to a 1-1 draw in Kazakhstan and missed a chance to qualify for the tournament in the United States, Canada and Mexico.
But Rudi Garcia's side, who lead Group J with two points more than North Macedonia, can still advance with a win over Liechtenstein on Tuesday in their final qualifier. The draw in Astana guaranteed the Belgians will finish in the top two.
Kazakhstan took a ninth-minute lead through 17-year-old Dastan Satpayev. Hans Vanaken levelled for Belgium in the 48th when the Club Brugge midfielder headed in a cross by Timothy Castagne.
But Belgium, which had routed Kazahkstan 6-0 in September, were unable to take advantage of playing with an extra man from the 79th minute after Islam Chesnokov was red carded for a hard challenge on Jeremy Doku.
