"I think that the first half was our best performance of the season, we were excellent. We didn't play as well in the second half but we had already done the damage in the first half," said Dillon, speaking to Teamtalk.com.
Reading had to cope without suspended captain John Mackie and also goalkeeper Marcus Hahnemann who was kept out due to injury.
Due to the absences the Royals reverted to a hugely effective 4-5-1 formation.
Dillon added: "We changed the tactics today, and we got it spot on. We reverted to a 4-5-1 formation and played Andy Hughes in the hole. He did superbly.
"In the second half Grimsby worked it out, but it was too late by then."
Reading fans will for a long time remember the game for the bizarre 90th minute third goal.
Forty-yards from goal Grimsby defender Alan Pouton slid in on Darius Henderson and as the pair collided the ball looped up and over the stranded Danny Coyne in the Mariners goal.
Whilst it went down as an own goal Dillon revealed that Darius will want to claim it: "It was an attempted tackle by one of their players, but Darius is going to claim the goal.
"I have never seen a goal like that before, I don't know where their keeper was."
Andy Hughes had opened the scoring for the Royals in the 13th minute of the game whilst Nicky Forster made it 2-0 just 20 minutes later, bagging his first of the season.