To convert kilometers to miles, you can use the following formula:
\[ \text{miles} = \frac{\text{kilometers}}{1.61} \]
Given that Timmy's van travels 30 kilometers per gallon of fuel, we can substitute this value into the formula:
\[ \text{miles} = \frac{30 \text{ kilometers}}{1.61} \approx 18.634 \]
Now, rounding this to the nearest tenth:
\[ 18.634 \approx 18.6 \]
Therefore, Timmy's van travels approximately 18.6 miles per gallon of fuel.