LPG / autogas conversion: UK vs US vs Germany
Unlike ethanol, LPG has a mature approval framework in all three markets, so the answer is less about whether and more about who signs it off.
All three markets reach the same verdict, conditional. What differs is the rule each one uses to get there, which is the third column.
| Market | Verdict | The rule that decides it |
|---|---|---|
United Kingdom DVSA / GOV.UK |
Conditional | Competent approved installer, tell DVLA and insurer The V5C fuel type is updated to gas or petrol, and the test checks the installation for leaks and secure mounting. |
United States EPA, NHTSA and state codes |
Conditional | EPA-recognised certified conversion system It must additionally carry a CARB EO in California and CARB states. A non-certified conversion is treated as emissions tampering. |
Germany StVZO / KBA |
Conditional | ECE R115 system approval plus installation test A recognised organisation carries out a gas-system installation test, then a change inspection and an entry in the papers. A recurring gas-system check follows, normally on the main inspection cycle. |
Germany is the only one with a recurring re-test obligation for the gas system itself, on top of the initial sign-off.
Why the answers differ
Is an LPG conversion legal?
LPG is the counter-example to E85, and comparing the two rows is more informative than either alone. Autogas has a mature approval framework in all three markets, so the answer is not whether but who signs it off. The US routes it through certified conversion systems and, in CARB states, an exemption order. The UK routes it through a competent installer plus notification to DVLA and the insurer. Germany builds the most process around it, requiring a system approval, a dedicated gas-system installation test by a recognised organisation, a change inspection and an entry, and then a recurring gas-system check on the main inspection cycle. That recurring obligation is unique in this dataset and is the part owners most often do not budget for.
Verdict at a glance
The same three markets, grouped by where they land.
Conditional
ConditionalUnited Kingdom, United States and Germany. Permitted, but only once the condition in the table above is met.
Sources
Primary legislation and regulator guidance behind each market's verdict.
- UKTell DVLA about changes to your vehicle (GOV.UK)
- UKMOT inspection manual: cars and passenger vehicles (GOV.UK)
- UKVehicle insurance (GOV.UK)
- USClean alternative fuel vehicle and engine conversions (US EPA)
- USAftermarket, performance and add-on parts (California Air Resources Board)
- Germany§ 41a StVZO - Druckgasanlagen, Flüssiggasanlagen (gesetze-im-internet.de)
- Germany§ 47 StVZO - Abgase (gesetze-im-internet.de)
- Germany§ 19 StVZO - Erteilung und Wirksamkeit der Betriebserlaubnis (gesetze-im-internet.de)
Other cross-market comparisons
This is a comparison of national rules, not legal advice for your vehicle. Rules change, and the US row in particular summarises federal law where one exists and the common pattern across states where it does not. Confirm the position in your own state or region before you buy or fit anything. Sources last reviewed July 2026.