Editing Compression ratio (section)

==Variable compression ratio engines==
{{Main article|Variable compression ratio}}
Most engines use a fixed compression ratio, however a [[variable compression ratio]] engine is able to adjust the compression ratio while the engine is in operation. The first production engine with a variable compression ratio was introduced in 2019.

Variable compression ratio is a technology to adjust the compression ratio of an internal combustion engine while the engine is in operation. This is done to increase [[fuel efficiency]] while under varying loads. Variable compression engines allow the volume above the piston at top dead centre to be changed.<ref>{{cite web |title=Variable Compression Engine |website=fs.isy.liu.se |url=https://www.fs.isy.liu.se/Lab/EngineLab/SVC/ |url-status=dead |archive-url=https://web.archive.org/web/20050311210702/http://www.fs.isy.liu.se/Lab/SVC/ |archive-date=11 March 2005}}</ref>

Higher loads require lower ratios to increase power, while lower loads need higher ratios to increase efficiency, i.e. to lower fuel consumption. For automotive use this needs to be done as the engine is running in response to the load and driving demands.

The 2019 [[Infiniti QX50#Second generation (P71A)|Infiniti QX50]] is the first commercially available car that uses a variable compression ratio engine.