I had the same thing happen to my Olga and a motorbike when I logged into my private server, which is running Nasdara, today. Gas is now empty in both and the radiator is also empty on my Olga.

I confirm the issue. It also occurs on the PC platform.

From testing some workaround: I tried Leak(FUEL, 21) and Fill(COOLANT, 5) directly on a persistent car after boot, and neither changed anything, even 6 seconds later. A car I spawned fresh from script did take Fill within 3 seconds. My guess is that these calls only take effect while the car is awake and simulated, and persistent cars are asleep with no player nearby. I haven't confirmed that.

https://steamcommunity.com/sharedfiles/filedetails/?id=3821410886 is a server side workaround, not well tested yet though.

I too can confirm the issue on PS5. To replicate:

• Fill a vehicle with fuel (& the radiator with water)

• Retsart the server

• Both the fuel & water are empty
  

We used this fix for the server, making some minor modifications (we added engine oil saving as well).
It doesn't always help. We have the Expansion Bundle installed, and vehicles disappear under the grid after an hour. We also have RaG_Immersive_Vehicles installed (which adds engine oil to vehicles).
In short, this fix doesn't provide a 100% solution.

Now the upload went trough

https://steamcommunity.com/sharedfiles/filedetails/changelog/3821410886

Vehicles lose fuel and coolant after every restart - i can confirm this bug

https://steamcommunity.com/sharedfiles/filedetails/?id=3821410886
now also supporting expansion helicopters + the deer isle helicopter (ATVs are normal cars)