Justify upgrade to C++11/14 from c++98 to my management

I work on a mixed codebase (Java/C++) of 1M-2M lines of code and we are upgrading our development environment to RHEL 7.3 and gcc from 4.5 to 4.8.5 which does give some (experimental) support for C++11.

The C++ code has been around for a few years and you would be hard pushed to find any use of STL containers as most of the current coders believe that c-style arrays and raw pointers are the most efficient way to code [we do a lot of signal processing stuff in the Defence domain]. We use a bit of Boost and ACE for threading/networking/timers/filesystem.

I need a few good reasons to present to management to persuade them that upgrading gcc to 6.1/2/3 would be beneficial. The most compelling argument would revolve around performance but given the heavy usage of c-style arrays and raw pointers I'm not sure that upgrading helps.

I am aware of the of the new language features such as lambdas, auto, threading, uniform initialization, smart pointers but don't know how to 'sell' these features. In fact, I think the new features might be seen as more of a hindrance as any usage of them would require the current developers to understand their usage.

There doesn't seem to be any reluctance to upgrade RHEL 7.3 to use Java 8 on the grounds that it contains the latest 'security patches' but upgrading C++ meets more resistance!