How much am I going to pay for fuel?

Hi I'm going to US in summer and I would like to know how much I'm going to spend for petrol.
I rent Ford mustang in Las Vegas (uses about 13 litres for 10km )and I'm going to grand canyon south rim, then to yellowstone and from there to San Francisco. From San Francisco I'm taking pacific highway to la and San diego. After that I'm returning back to vegas. I'm going yo spend about three weeks in these cities therefore you need to add some little milage that is going to be driven within this cities.
I worked out I'm looking at 500 $is that right?
I'm aware that fuel price is different in each state and I tried to include it in my calculations
Tell me what you think and did you count.

There's a website - www.gasbuddy.com - that shows fuel prices in almost all areas ; you can use that for estimates on the price of fuel where you will be travelling + you can use the google maps feature to get estimates of the amount of miles from point A to point B… Using those sites will give you a good figure of fuel costs

Sounds about right. Grand Canyon is odd bc LV to GC then you will have to drive back to LV(10 hours) to Yellowstone. May I suggest a bus tour to GC from LV. You will only get to see GC for an hour of so only with the bus. Would suggest to stop by Zion and Bryce Canyon on you way up to Yellowstone. Fill up the tank before coming into California. Drive hwy 1(PCH)/101 from SF to LA. Unless you want to drop by Yosemite. Consider getting an annual National Park pass.

I would think $500 for gas would be about right. Depending where you get gas finding the right price and some states have cheaper gas.