Chip Ganassi Racing's Dixon suffered an issue with his 2.2-liter, twin-turbo Honda V6 on his final run in Friday practice that he said puts his team "on the backfoot". He has started on pole for the last two Indy 500s, and has five to his name compared to Mears' all-time record six.
After installing a fresh engine from Honda's pool of motors, Dixon returned to the track in Saturday morning's available half hour of running to run-in the new power unit.
"It's just a bit of a process, you've got to get miles on it, so it definitely puts you in a bit of a compromised position," he told NBC Peacock. "We tried to get some miles on it this morning, and we'll try again later [in qualifying] – we may have to do a few runs to get everything dialled in.
"I think the car's good, we made some changes on it last night. Yesterday was decent but we just had a bit of an issue there."
When asked when the peak power of these engines becomes available, he replied: "I think there's a sweet spot, I don't think that's it at the start or the end [of their life cycle] but it is one of those things of trying to get them to be dialled in.
"They're very sensitive, each cylinder needs its own special thing so, it is what it is, we can't do anything about it and we'll just have to try a little bit harder to get the most out of it."
His team-mate Alex Palou also required a new motor but set the third-fastest time in Saturday practice, compared to Dixon's fifth-quickest lap, and remains confident of a good showing in qualifying later today.
"The guys did an overnight engine change, so we just wanted to check that everything was right," he said. "The car is fast again, so really pleased with that. I feel it could be a good day for us.
"It's pretty close so I don't think it will be easy to get into the Fast 12, it's going to be really challenging, so it will depend on the third and the fourth lap, to try and be consistent as possible.
"Hopefully we'll get all four Ganassi cars into the top 12."
The two-day qualifying process begins at 11am local time, and the pole won't be decided until Sunday afternoon.
