> ## Documentation Index > Fetch the complete documentation index at: https://playbook.smedleygroup.com/llms.txt > Use this file to discover all available pages before exploring further. # Fuel Correction > Why lap times are adjusted for fuel burn, where the numbers behind it come from, and which widgets use it. ## Overview A car gets faster over a race simply by burning fuel and getting lighter, independent of anything the driver or tyres are doing. Fuel correction removes that effect from a lap time, so you can compare a driver's pace lap to lap, or stint to stint, without the comparison being skewed by how much fuel was on board at the time. *** ## How It Works ### The Corrected Laps Insight A dedicated metric, `corrected_laps`, computes this every time a lap completes. For each lap it works out how much fuel the car was carrying, and applies a per-round sensitivity figure (seconds of lap time per kilogram of fuel) to convert the raw lap time into a fuel-corrected one. Its output carries the driver, lap number, the raw lap time, the estimated fuel mass at that point, and the corrected time. Fuel correction is one part of a shared correction pipeline that other metrics build on too: the tyre degradation metrics (stint-level and compound-level degradation, and race pace) all consume the same fuel-corrected numbers before fitting a degradation curve, so a change to the fuel correction maths flows through everything downstream of it rather than being reimplemented per widget. ### Where the Numbers Come From The sensitivity used to correct laps for fuel isn't a constant in the code. It's an event parameter, loaded per season and round from timing data: a fuel effect in seconds per kilogram, the estimated fuel load at the start of the session, and an estimated burn rate per lap. These are versioned rows, resolved for the specific round being watched. If those parameters haven't been loaded yet for a round, the metric doesn't guess. It withholds its output for that lap rather than publishing a corrected time built on an invented number. The same applies when the raw lap time itself isn't available yet. **Practice is a distinct case, not a silent one.** The metric runs on practice sessions too, but a practice car's fuel load is genuinely unknown rather than merely unloaded, so it never invents a fuel figure there. The row is published with no fuel mass and a corrected time equal to the raw time, plus an explicit marker saying the correction is absent because practice fuel is unknown. The webapp reads that marker and labels the mode "Uncorrected (practice fuel unknown)" instead of implying a correction that did not happen. Qualifying, and any session that cannot be positively classified, withhold entirely. *** ## Where You See It in the App A shared raw/fuel-corrected toggle appears on the **Lap Times** chart, the **Laps** table, the **Stints** viewer and the **Stint Lap Times** viewer. Each keeps its own toggle state, but they share the same underlying data: if fuel-corrected numbers aren't available for the session, the corrected option is disabled with the reason as its title rather than silently showing raw data under a corrected label. Several other widgets consume fuel-corrected data without an explicit toggle, because correction is baked into what they're modelling: **Corrected Laps Plot** shows the corrected times directly, and **Deg Fit Plot**, **Tyre Deg Table**, **Tyre Deg Ranking** and **Tyre Strategy** all build their degradation curves and rankings on top of the same fuel-corrected foundation. *** ## FAQ > **Why is the fuel-corrected option greyed out on a widget?** > > The event parameters for that round (fuel sensitivity and load) haven't been loaded yet, so the corrected laps metric has nothing to compute from. Raw lap times are still shown; only the corrected view is unavailable until the parameters land. > **Does fuel correction apply to practice and qualifying?** > > A real fuel correction applies to race and sprint sessions, where the fuel load is known and genuinely changes over the run. Practice sessions still get corrected-lap rows, but with no fuel correction applied and a label saying so, because a practice car's fuel load is unknown. Qualifying withholds entirely. *** ## Next Steps > **[Insights and Versioning](/software/internal/watchparty/concepts/insights-and-versioning)** > > How this and every other metric is versioned and kept honest. > **[Lap Times](/software/internal/watchparty/widgets/lap-times)** > > See the raw/fuel-corrected toggle in context. > **[Corrected Laps Plot](/software/internal/watchparty/widgets/corrected-laps-plot)** > > The dedicated widget for fuel-corrected lap times. > **[Tyre Deg Table](/software/internal/watchparty/widgets/tyre-deg-table)** > > Degradation modelling built on the same corrected data. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.