Im about to go in for my 37500 service. While scheduling it, I asked the service adviser what all was involved. Of all the things that were recommended, the flushing of the fuel system for $150 really stood out. Ive been working on cars for all my life and I generally keep cars until 300k miles or more. The only time Ive ever flushed or otherwise performed major maintenance to the a fuel system is after a fuel pump failure, load of bad gas, or get tons of water in the gas. And in that case, I generally install a new filter and flush fresh fuel through the system and out the test port or return line. Then again, consider the unique fuel system in the Volt and that I drive mine 90% EV, is it needed?