To convert the fuel efficiency from kilometers per gallon to miles per gallon, we can use the conversion factor that 1 mile is approximately equal to 1.61 kilometers.
Given that Erika's car gets 30 kilometers per gallon, we can calculate the distance in miles as follows:
\[ \text{miles per gallon} = \frac{\text{kilometers per gallon}}{\text{kilometers per mile}} = \frac{30 \text{ km}}{1.61 \text{ km/mile}} \approx 18.63 \text{ miles per gallon} \]
Now, rounding this to the nearest tenth:
\[ 18.63 \text{ miles per gallon} \approx 18.6 \text{ miles per gallon} \]
Thus, Erika's car travels approximately 18.6 miles per gallon of fuel.