Recently I came back to Avast (I used you once before) from AVG as that was also using a lot of the CPU.
One thing I noticed as soon a it was installed was CPU usage again
I do have a screenshot but the insert images function doesn't work on your forums but here what it says.
There is an advertisement from Avast to hassle me to "Activate your PC optimization tool" for £1.25 a month for a period of time. Before this it said that I had performance issues. The only performance issues I have is what Avast has caused as my PC is clean (Clean reinstall of Windows 10), uses Malware Bytes Pro and has Pro Advanced System Care so what Avast has picked up is only minor to my performance issues or is something that avast created to get me to buy this addon tool. It uses between 50% and 70% consistently as well as around 3MB/s constant disk usage. I do hope this fixed otherwise I will be moving again to another popular antivirus software.
