Official fuel economy comes from a laboratory test. Nobody publishes how far real cars miss it. Across 8,216 engines with an owner-reported average set against the official combined figure for the same engine, the typical car tested on the old NEDC cycle returns 82% of its official MPG and the typical WLTP-tested car returns 94%. The newer test closed most of the gap, not all of it. The full engine-level data is free to download below and free to reuse with a link.
| Real-world result | NEDC-tested engines | WLTP-tested engines |
|---|---|---|
| Beats the official figure | 410 (6%) | 392 (30%) |
| 90 to 99% of official | 1,320 (19%) | 488 (37%) |
| 80 to 89% of official | 2,486 (36%) | 283 (21%) |
| 70 to 79% of official | 2,162 (31%) | 84 (6%) |
| Under 70% of official | 510 (7%) | 81 (6%) |
| Total engines | 6,888 | 1,328 |
Two thirds of NEDC-era engines land between 70% and 89% of the brochure figure. About one engine in ten across the whole dataset beats its official number.
One row per engine: make, model, generation and years, engine, test basis (NEDC or WLTP), the official combined figure (range and midpoint), the owner-reported average and range, real as a percentage of official, submissions per generation, the live page and the archive source. About 2 MB. Method and licence as plain text.
Free to quote, chart and republish, including commercially, if you credit Car Advert Check and link to caradvertcheck.co.uk/real-mpg. Please keep the test name beside the figure: “82% under NEDC, 94% under WLTP”, never a bare “82%”. Press enquiries: hello@caradvertcheck.co.uk.
Each engine’s owner-reported average is divided by the official combined figure for the same engine, giving real as a whole percentage of official. The official figure is the one the car was type-approved on: NEDC for cars tested before the switch in 2017 to 2018, WLTP after. Where the archive held a range for the official figure, its midpoint is used. NEDC and WLTP results are never compared with each other. The medians are of that percentage, split by test basis. All MPG is in imperial gallons.
The owner-reported averages are rebuilt from the archived Honest John Real MPG tables, which went offline when the site closed in August 2026, plus new submissions from readers of this site. Every model page links to the archive snapshot it was built from. How the rebuild was done. Figures on this page are recomputed from the dataset at every site build; this build: 10 October 2026.
Car Advert Check is not affiliated with Honest John or Volkswagen Financial Services. Owner-reported figures depend on how and where people drive; a single engine’s percentage is a guide, the medians are the robust number.
Looking for one car? Search the Real MPG checker by make and model, or read why real MPG is lower than the official figure.
Fuel economy is one line on the running-cost sheet. These cover the rest of buying a used car without getting stung.