PHEV mileage & running cost — full analysis

BYD Sealion 6 · 8 fill-ups tracked · Dec 2025 – Jul 2026

Disclaimer: Efficiency figures, cost calculations, and usage splits are derived from odometer and meter readings you provide. Accuracy depends on the accuracy of those inputs. Values are for personal tracking purposes and should not be used for warranty claims, tax filings, or official reporting without independent verification.

Generated by PHEV Tracker: https://github.com/marfillaster/phev-tracker

Last Refuel

Usage: 32.6% F / 67.4% EV (last) · 35.0% F / 65.0% EV (cumulative)

* Combined efficiency: EV cost converted to equivalent fuel liters

Cumulative

* Combined efficiency: EV cost converted to equivalent fuel liters

Executive Summary

• 9,600 km tracked · ₱36,222 spent · 65% EV across Dec 2025 – Jul 2026 (221 days).
• Running cost is ₱3.77/km, against roughly ₱5.50/km for a comparable mid-size ICE SUV — about ₱16,600 saved over the tracked distance.
• Cost per kilometre rose from ₱3.24 (Mar) to ₱4.76 (Jul). Pump price accounts for almost all of it: fuel went from ₱53/L to ₱82/L over the same period.
• July's tank covered a provincial round trip and reads 11.57 L/100km, the highest in the log. It is a tank-to-tank measurement. A single interval's efficiency is not a reliable signal on this vehicle; telemetry from the trip puts the charge-sustaining driving at about 14.8 km/L.
• Battery SOH is 99%, rechecked 2026-08-02. Next service is time-triggered, around Sep 2026.

AI Analysis

1. Efficiency trends — Fuel efficiency sat in a tight 8.12–9.45 L/100km band for the first seven intervals, then read 11.57 L/100km in July. EV-mode efficiency has held between 5.35 and 6.53 km/kWh apart from two outliers in early July. There is no drift with accumulated mileage across the record.

2. Cost optimisation — EV running costs ₱2.62/km against ₱5.92/km on fuel, so every kilometre moved from fuel to plug saves about ₱3.30 at current prices. That gap has widened as pump prices rose: in December the spread was nearer ₱2.20/km. EV already carries 65% of cumulative distance, and the remaining fuel kilometres are mostly long-trip distance that plug charge cannot reach.

3. Usage patterns — EV share climbed from 48% in the first tracked interval to a 76% peak in June, and has been noisier since: 74%, then 38%, then 67%. The 38% interval was a road trip. Local driving stays in EV mode on overnight charging; the share drops whenever a long trip puts distance beyond the battery's range.

4. The limits of per-interval efficiency — A single interval's L/100km moves with the mode mix and with the amount of regenerative braking collected, and that movement usually cannot be explained from the log. July's 11.57 L/100km reflects this rather than an efficiency loss. The drivetrain section below sets out the mechanism and the trip telemetry.

5. Anomalies — Three, all explained, none mechanical. (a) A 101-day gap between the March and June fill-ups: the car was in for radiator replacement. (b) Pump price paid rose from ~₱53–59/L to ~₱70–82/L across June and July, tracking a regional supply-driven spike rather than any change in consumption. (c) EV-mode efficiency swung from 4.08 to 16.06 km/kWh across two fill-ups six days apart in July; taken as a pair they give 5.46 km/kWh, so a charge landed on one side of a fill-up while the kilometres it powered fell on the other.

6. Performance comparison — At ₱3.77/km the car sits inside the ₱3–4/km band typical of a mid-size PHEV SUV and well under the ₱5–7/km of a pure-ICE equivalent. EV-mode efficiency of 5.74 km/kWh is at the lower edge of the 5.5–7.0 km/kWh class range, which is consistent with a heavy vehicle in a hot climate running air-conditioning almost continuously.

7. Recommendations — Keep charging overnight: the fuel-to-plug spread is ₱3.30/km and widening. Use cost per kilometre rather than individual tanks to judge running cost; the per-tank measurement cannot support that comparison. Recheck SOH around March 2027, far enough from the last reading to establish a degradation rate. The time-based service trigger arrives around Sep 2026, well before the 40,000 km trigger.

How the Drivetrain Works, and Why Per-Trip Efficiency Misleads

The car draws propulsion energy from three places and meters one of them.

The two modes. On a full charge the car runs in EV mode, propelling on battery alone until state of charge reaches roughly 25%. Below that it switches to HEV mode, where the engine either charges the battery or drives the wheels directly, depending on power demand; high speed and uphill sections bring the engine into direct drive. The EV odometer advances only while EV mode is active, so the HEV and EV distance columns count modes, not energy.

Three sources, one meter. In HEV mode the energy reaching the wheels comes from the battery, from regenerative braking, and from the engine. The plug meter counts electricity drawn from the wall. There is no meter for regen, and none for charge the engine produces through the onboard generator. The log records how much fuel and how much mains electricity went in, and cannot attribute any given kilometre to either.

Two effects follow, in opposite directions. Plug charge still in the pack at the switchover is spent as HEV kilometres, which raises apparent fuel efficiency. Regen adds unmetered energy to both columns. Neither is measurable here.

Effect on a per-trip figure. A trip's consumption figure depends on where the trip started in the charge cycle. On the provincial round trip in this log, the outbound leg began on a full battery and ran its first 150 km on plug charge with the fuel gauge nearly stationary, then continued in charge-sustaining mode. The return leg began at 19.5% and ran on fuel throughout. Measured over charge-sustaining running only, same route and same load, the two legs came within 1% of each other at about 14.8 km/L, against a cumulative figure of 11.0 km/L. Measured as whole trips, they differ by roughly a factor of two.

Counted readings and estimated ones. The gap above is in coverage, not accuracy. The three quantities this log uses are counted directly: the odometer counts distance, the plug-side meter counts mains kilowatt-hours, the pump counts litres. What the car does not provide is a meter for regen or for the onboard generator.

The dashboard's estimating readouts drift. The 35.06 L fill raised the fuel gauge 64 points; 64 points of a 60 L tank is 38.4 L, so the gauge reads full about 3.3 L early. Over the return leg the gauge implied 27.6 L consumed where the trip computer's injector count gave 22.4 L, a 23% difference in the upper part of the tank. The 14.8 km/L figures above are derived from the gauge and are approximate, and their distances come from integrating the speed feed, which ran about 5% above the odometer.

The fuel side is tank-to-tank. A fill records how much fuel was consumed since the last one without depending on an estimate. With the odometer and the energy meter, that gives three counted inputs. Efficiency over a single interval still carries the attribution gap above; the distance, fuel, energy and cost totals do not.

Cost per kilometre needs no attribution. Pesos spent at the pump, plus pesos spent on metered electricity, divided by kilometres driven. It is the figure this report leads with, and the one to use when comparing against another vehicle.

Inferred Insights

Time-based:

• Refuel cadence averaged ~29 days across the tracked period; excluding the 101-day service gap, ~19 days.
• Daily average: ~43 km/day over the 221-day tracked window.
• Projected annual distance: ~15,900 km/year at the current pace.
• Projected annual spend: ~₱59,800/year at current prices and usage mix.
• Next refuel: roughly 2–3 weeks out on recent cadence.

Savings & Environment:

• Savings vs ICE over the tracked window: ~₱16,600 across the 9,600 km actually logged, using a ₱5.50/km mid-size-SUV ICE benchmark.
• This is the measured figure and covers only the tracked period. The 32,021 km lifetime odometer includes ~22,421 km driven before tracking began (Sep 2024 – Dec 2025), for which no fuel or energy split exists.
• Extrapolated lifetime saving: ~₱55,300 across the full odometer, applying the tracked period's ₱3.77/km against the ₱5.50/km benchmark. This assumes the untracked driving had a similar mix and pricing, which is unverified — a rough estimate, not a measurement.
• CO₂ avoided: ~760 kg over the tracked period. The 6,240 EV kilometres would have needed ~567 L of fuel (~1,305 kg CO₂ at 2.3 kg/L); the 1,087.5 kWh drawn to cover them carries ~544 kg at the Philippine grid average of ~0.5 kg CO₂/kWh.

Battery Health:

• SOH 99%, rechecked 2026-08-02 — unchanged from the March reading, and healthy.
• Estimated charge cycles: ~59 full-equivalent from plug energy (1,087.5 kWh / 18.3 kWh pack). This undercounts real cycling, since charge produced by the onboard generator is not metered and does not appear in the plug total.
• A degradation rate still cannot be derived: two readings four months apart both report 99%, which sets a floor on health but gives no slope.

Trends:

• EV usage: rose from 48% to a 76% peak, then became trip-dependent rather than trending.
• Fuel price paid: ₱53.04/L (Dec) → ₱82.30/L (Jul), a 55% rise, and the dominant driver of rising cost per kilometre.
• Efficiency vs mileage: flat across the tracked range. No degradation signal.

Predictions:

• Next refuel: ~2–3 weeks out.
• Next service: due around Sep 2026 on the 12-month trigger, or ~Feb 2027 at 40,000 km on current pace — the time trigger lands first. Inferred from mileage and acquisition date only; no service records are tracked here.

Data Sources

• data/phev_log.csv - refuel log (odometer, plug meter, fuel, tariff) backing every figure above