For the most part, I leave the PC's motor vehicles to be powered by Handwavium. It's covered in basic lifestyle/vehicle costs, you can always be assumed to have some gas in the tank to drive across Seattle, I'm always going to assume the steely-eyed professional criminal thought to gas up before the heist, etc, etc. Much like basic clothing and basic food, I'm fine with handling it largely "off screen" and letting it fall under lifestyle costs. Real life is where we worry about rising gas costs, wearing out our clothes, and grocery shopping. In a few Shadowrun games I've run, I haven't even had players keep track of basic ammo purchases (only having them spend money on the good stuff), just to cut down on bookkeeping.
But...if it should become an issue, it can become an issue. "Extra Fuel Tank" and similar mods from Arsenal exist for, well, making it an issue. When the PCs are doing more than cruising across the Metroplex for a Meet -- say, off-wheeling across the open country on a long distance smuggling run -- then it might start mattering. I'd call it 10 nuyen per hour of driving time (so a default "full tank" costs 60 nuyen), and let them look over the vehicle rules for options, add-ons, and modifications they could make to prepare a vehicle for a long haul trip.
Like probably 75% of the vehicle customization in Arsenal (in my experience), it's not going to come up most sessions, with most groups.