You pay tax on any particular amount per gallon offered so you aren't going to pay $3.85. It is NEVER, EVER a good idea to accept Hertz refill option. We've discussed this in many other threads in this forum. Please do a search.

At LAX, you will pay another 9% (Los Angeles City sales tax) + 3.75% (fuel only tax...so you are not JUST paying the "usual" taxes) on top of the $3.85 (I know, I am fighting being charged for gas from an award reservation from last week and these were the taxes added at LAX for gas alone - which was $9.78 per gallon last week at Hertz). That's low compared to other airport locations. Gas can be had in the LAX area for less than $3.85 per gallon today.

Adding the taxes from Hertz to a $3.85 gallon of gas offered by them, you are really paying $4.34 per gallon. I do not know of any station in the LAX area that has self service gas, today, that high. BAD IDEA!

Update: The Arco gas station on La Tijera just west of the 405 freeway is $3.85 today per http://www.losangelesgasprices.com (zipcode for Hertz LAX is 90045).