How much fuel you need, lap by lap.
Every lap it works out how much fuel you need to finish and how many stops that takes, based on what you're actually burning.
It keeps track of your fuel during the race, tells you when to box, and can set the right amount of fuel in iRacing's pit menu for you.
Free. No account. Independent third-party app, not affiliated with iRacing.

On the left, Race Engineer's call: box this lap, add 6.8 L. On the right, iRacing's pit menu already set to 7.0 L. You didn't touch anything.
The call is also spoken, in English, Portuguese or Spanish.
Recorded in test mode, which simulates the end of a race so you can try it in practice. The fuel goes into the car as usual. How to try it yourself →
You stop in your box and iRacing adds what was set: the tank goes from 38.1 L to 43.3 L, without you opening the pit menu.
Every lap it works out how much fuel you need to finish and how many stops that takes, based on what you're actually burning.
It tells you when you can already stop and the last lap you still can.
It reads iRacing's own telemetry, and only sends the chat messages you chose.
In a short race, iRacing's own fuel calculator is enough. Race Engineer makes the difference in long races, when there's a safety car, when you need to save fuel, or when the race ends up longer than you expected.

Lap times, fuel used, pit stops and cautions are saved for each car and track. You can open an old race and see how the strategy played out. Everything stays on your computer, with no account.
When a new version is out, the app lets you know and updates with one click, whenever you're not connected to iRacing.