Prueba con:
Código PHP:
echo "<table><tr>";
echo "<td>$arr[$x]['Marca']</td>";
echo "<td>$arr[$x+1]['Marca']</td>";
echo "<td>$arr[$x+2]['Marca']</td>";
echo "</tr><tr>";
echo "<td>$arr[$x]['Combustible']</td>";
echo "<td>$arr[$x+1]['Combustible']</td>";
echo "<td>$arr[$x+2]['Combustible']</td>";
echo "</tr><tr>";
echo "<td>$arr[$x]['Combustible']</td>";
echo "<td>$arr[$x+1]['Combustible']</td>";
echo "<td>$arr[$x+2]['Combustible']</td>";
echo "</tr></table>";