Real MPG: real-world fuel economy against the official figure, by engine (UK)
Car Advert Check, https://www.caradvertcheck.co.uk/real-mpg/official-vs-real
Exported 2026-10-10. 8,216 engines across 830 models and 65 makes.

LICENCE
Creative Commons Attribution 4.0 International (CC BY 4.0). Free to reuse, quote and republish,
including commercially, provided you credit "Car Advert Check" and link to
https://www.caradvertcheck.co.uk/real-mpg. The owner-reported averages are rebuilt from the archived Honest John
Real MPG tables (Honest John closed in August 2026); Car Advert Check is not affiliated with
Honest John. Nothing in this file identifies a person.

HEADLINE FIGURES (recomputed from this file)
Median real-world economy as a share of the official combined figure:
  NEDC-tested engines: 82% (6,888 engines)
  WLTP-tested engines: 94% (1,328 engines)
Always quote the two figures with their test names. "Cars return 82% of their
official MPG" without "NEDC" is not supported by this data.

Distribution (engines):
  Beats the official figure    NEDC   410 (6%)   WLTP   392 (30%)
  90 to 99% of official        NEDC  1320 (19%)   WLTP   488 (37%)
  80 to 89% of official        NEDC  2486 (36%)   WLTP   283 (21%)
  70 to 79% of official        NEDC  2162 (31%)   WLTP    84 (6%)
  Under 70% of official        NEDC   510 (7%)   WLTP    81 (6%)

METHOD
real_pct_of_official = real_mpg_avg / official_mpg_mid, for the same engine, as a whole percent.
official_mpg_mid is the official combined figure the car was type-approved on (NEDC up to 2017-18,
WLTP after); where the archive held a range, min and max are given and the midpoint is used.
NEDC and WLTP figures are never compared with each other. Medians are of real_pct_of_official,
split by test_basis. All MPG is in imperial gallons (4.54609 litres).

COLUMNS
make, model, generation, years_from, years_to, van (true for a van base), engine,
test_basis (NEDC or WLTP; blank when no official figure was held, so no percentage),
official_mpg_min, official_mpg_max, official_mpg_mid,
real_mpg_avg (owner-reported average), real_mpg_min, real_mpg_max (owner-reported range),
real_pct_of_official, generation_submissions (owner submissions counted per generation in the
source, not per engine), page_url (the live page), source_archive_url (archive.org snapshot the
row was rebuilt from).