From the above results, it is observed that the F-statistic value is 17.94 and it is highly significant as the corresponding p-value is much less than the level of significance (1% or 0.01). Thus, it is wise to reject the null hypothesis of equal mean value of mileage run across all the tyre brands. In other words, the average mileage of the four tyre brands are not equal.
Now you have to find out the pair of brands which differ. For this you may use the Tukey’s HSD test.
ANOVA is a fairly simple test, but it can be quite useful to know.