This serves as an excellent workout as well as an FTP test. Even if the result isn't stellar, it's still worth doing. Don't worry about any drops or tiny improvements.
The first interval is a warm-up. Keep the power steady and consistent here to make sure you're not cooking yourself for the real test.
5x5min @55-65rpm; RBI 5min @90+ rpm
Last minute of each HARD @55-65rpm
Power on intervals:
Notes: Make sure the rest period is 95+ rpm. You can ride as easy or as hard as you want for the rest period.
Keep it easy.
Can be substituted for a longer ride of 4+ hours, or a group ride.
Additionally, this workout's rest period can be dropped to half the working interval in order to cut the total duration to ~2 hours.
The rest of the ride should be easy, at or under 70% of FTP.
Intervals on 20min
6x7min @steady state; RBI 13min