If your US friend tells you how many mpg the car uses you can use the RTA Gas calculator. You can use gas buddy to get an idea of fuel costs in various States, but I generally use $3 per gallon. Being from the UK I usually work with that a meal here costing £20 will be about $20 in the US and so on, [Groceries, Hotels ] with the exchange rate being the benefiting factor. It's not an exact science, but because everyone is different in where they eat and what is considered a decent meal etc, it gives a good indication.