I was looking at Oakland Airport recently as I had got a good flight price. We are not going after all but there seems to be plenty of choice. I just looked for rough costs at that time. Oakland Airport has a list of transport options. You might want to look at the door to door shuttle - United Shuttle
I also found a range of options here You will see pre bookable uber for instance.
Finally I did find an option through Viator at £71 - private transfer. I think you could get cheaper private transfers elsewhere. I only had a quick look and would have researched further when we booked- I just needed an idea of prices.

thanks Fiona. i will have a look when i get home, i too got a great price with Norwegian out of gatwick, we flew with them to New York and Majorca and i can't fault them

I have been hearing good things about Norwegian! Must try them sometime.

they are good we have had no problems at all low prices and flying on a dreamliner, a tip is if and when you book pay extra for the nice "n" tasty option that gives you meals, a suitcase in the hold and most importantly pre book your seat, my wife and I have extra leg room both ways at no extra cost, otherwise you just get a seat allocated to you

Good to know!