Diesel will get used excessively and you will get more road wear, as the user proposed. If you tax it, you will pay more directly for goods, but as costs rise people will be incentivized to find more efficient transport solutions.
It might still be worth it if road wear is cheap or the predictable misuse is predictable and that saves money somehow, but in all likelihood little harm would come from a fair treatment of diesel vs. gasoline etc. taking into account road wear of each vehicle class. It would be more natural to tax vehicle weight, hours driven etc. directly based on a sound model of societal cost though.