Cooling issue on highway

[1] And lots of people use 180 [ or 160 ] thermostats in their old cars NOW. When these cars were made, the fuel had lead in it which cooled the combustion process & reduced the chance of detonation. No lead to day, cooler engine by whatever means, to reduce chances of detonation.
[2] New cars have much more alum in them than old cars [ look it up ]. Easier to cool because of it's greater thermal conductivity compared to CI.