CPU-usage on 4.* compared to older versions

Has any measurement been made on the consumption of CPU on new versions, compared to the older ones? We run a professional site with usually around 40 site views per second.
Previously we used version 2.25.1, but we have now updated to version 4.6.0.
Afterward we have been measuring the differences and the new version seems to use twice as much CPU. Could this be because the old version was more lightweight and complexity has increased in newer versions? We use a number of systems for cache and performance optimaiton,
but this was still not what we wanted to happen after updating to a new version.