From Sacramento to LA area..mid day during week..mid Feb.
Renting a car & driving to Oxnard...
Actual miles similar but have no idea about --ease of car rental ....freeway issues ???
Flying into Santa Barbra would be closer to Oxnard but expensive..also neither of my airlines (for which I have miles to use fly there)

Burbank . . .

Or you could fly into LAX and take Lincoln up to Santa Monica and then cut over to the PCH up through Malibu and then take Rice to get to Oxnard. This would avoid all but maybe 5 miles of freeway.

I mentioned Burbank because LAX is such a zoo. Burbank is easy peasy.

It takes longer to get out of LAX and then shuttle to the rental cars, so if you are arriving mid-day and if it's a weekday, I would choose Burbank. You walk out of the terminal and then it's a 4 min walk to the rental car center and you're into your car within 5 minutes usually.
Hopefully by mid-day you mean by 2pm, because at 3pm the freeways start getting congested and stay that way until 7pm , from either airport.

From Burbank you also have option of train service out to Ventura in case it's raining cats n dogs and you don't want to join in the bumper car battle on the freeway.

I agree with janisj and clarkgriswold. If you don't want to rent a car, the Amtrak/Metro station is directly across Empire Avenue from the entrance to the Burbank airport. The fare on Amtrak from BUR to OXN is in the $20 range. The seats on the Pacific Surfliners are unreserved so if you miss one, your ticket is good on the next one

Burbank. We used to live near there, now live in Sacramento. Going to Oxnard Burbank is the best choice. You can walk to the car rental area and be on the 101 in relatively easy time.

Burbank is my new favorite airport, we’ve used it three times in the past three months around the holidays and it’s a dream compared to LAX! Santa Barbara is also nice but as you’ve mentioned, usually more expensive. SBA and BUR are your best choices.

If you wanted to stay on the ground from Sacramento to Oxnard, you have a couple of choices. If you can leave Sacramento at 6:35AM, you can get on the Amtrak Coast Starlight and be in Oxnard in about 12.5 hours (around 7PM). If you can't leave Sacramento until after noon, you get an Amtrak bus at 12:41PM to Stockton where you get on a San Joaquins train all the way to Bakersfield. At Bakersfield you get on another bus (2hr20min) to Oxnard arriving about 9PM.
The Coast Starlight stops in Santa Barbara about 6PM which is probably late to rent a car.

Which airlines? Would be good to know before recommending an airport if you're set on using either of those airlines.

Really interesting about LAX vs Burbank..shows how
"miles" don't always tell the time involved..
Thanks everyone....