Suzuki skipped required coastdown tests on 26 models; the retests beat the catalog anyway

In 2016, with Japan's transport ministry scrubbing certification files after the Mitsubishi mileage-fraud case, it emerged that Suzuki had never run the legally prescribed coastdown test — rolling a car to a stop on a road to measure its driving resistance — for the fuel-economy figures in its filings. Suzuki confirmed the scope: 26 models covering 2.14 million vehicles. Instead of the road test, engineers stacked indoor wind-tunnel drag with component-level resistance values, then entered fabricated test dates, weather and coastdown times into the ministry's forms.

Suzuki's public explanation kept shifting. The first press conference argued that stacking indoor component measurements could replace the road test; the story then became that one representative model had been road-tested with variants corrected by component data, which the company said Europe accepted. Nikkei's technology columnist tracked the shifting accounts and concluded the substitute was never an equivalent of the prescribed test. Suzuki said staff had no intent to cheat, and its report found no material gap between the methods.

The government's confirmation tests settled it. On August 30, 2016 the transport ministry published NASVA's retests: all 26 current Suzuki models — 28 vehicles — delivered fuel economy above the filed figures, unlike Mitsubishi, whose tested cars came in up to 8.8 percent below spec and were ordered to correct them. Suzuki paid no fine, but on June 8, 2016 chairman-CEO Osamu Suzuki had given up the CEO title and the vice-president in charge of technology had left. A fraud that never moved a number still ended a CEO's job.

No fine. Chairman-CEO Osamu Suzuki gave up the CEO title and technology VP Osamu Honda resigned; 26 models' mileage paperwork was refiled under ministry oversight.

The shortcut was process fraud, not results fraud: engineers trusted their substitute physics, so for years nobody inside saw a reason to run the expensive road test the regulation actually requires.

The defense moved across press conferences — from 'stacking works' to 'Europe allows it' — and each revision made the company look worse even though the underlying numbers held up.

Certification filings went unreviewed internally: fabricated test dates and weather sat in ministry paperwork for years without anyone asking why the measurements never came from the road.

The people who benefited from a passed certification were the same people documenting the test — an audit-proof process needs separation the testing culture didn't have.

Paperwork shortcuts survive until someone reads the files. Suzuki's fuel numbers were honest, but the skipped test runs still cost the CEO his title: results without an auditable process don't count.

The ministry accepted Suzuki's refiled, compliant measurements, and NASVA's August 2016 confirmation tests showed all 26 current models exceed their filed figures. Suzuki switched its official road-load method from stacked estimates to real coastdown runs, which improved the catalog values. No fine and no criminal case followed; the price was Osamu Suzuki surrendering the CEO title and the technology vice-president's resignation. The case became the standard contrast with Mitsubishi's results fraud: a broken process with honest numbers is still a scandal that reaches the top.