Editing Fuel efficiency (section)

=== Hydrogen fuel cells ===
In the future, [[hydrogen vehicle|hydrogen cars]] may be commercially available. Toyota is test-marketing vehicles powered by hydrogen fuel cells in southern California, where a series of hydrogen fueling stations has been established. Powered either through chemical reactions in a [[fuel cell]] that create electricity to drive very efficient electrical motors or by directly burning hydrogen in a combustion engine (near identically to a [[natural gas vehicle]], and similarly compatible with both natural gas and gasoline); these vehicles promise to have near-zero pollution from the tailpipe (exhaust pipe). Potentially the atmospheric pollution could be minimal, provided the hydrogen is made by [[electrolysis]] using electricity from non-polluting sources such as solar, wind or [[hydroelectricity]] or nuclear. Commercial [[hydrogen production]] uses fossil fuels and produces more carbon dioxide than hydrogen.

Because there are pollutants involved in the manufacture and destruction of a car and the production, transmission and storage of electricity and hydrogen, the label "zero pollution" applies only to the car's conversion of stored energy into movement.

In 2004, a consortium of major auto-makers — [[BMW]], [[General Motors]], [[Honda]], [[Toyota]] and [[Volkswagen]]/[[Audi]] — came up with ''"Top Tier Detergent Gasoline Standard"'' to [[gasoline]] brands in the US and Canada that meet their minimum standards for [[detergent]] content<ref name="Top Tier Gasoline">[http://www.toptiergas.com/retailers.html Top Tier Gasoline] {{webarchive|url=https://web.archive.org/web/20130815031514/http://www.toptiergas.com/retailers.html |date=2013-08-15 }}</ref> and do not contain metallic additives. Top Tier gasoline contains higher levels of detergent additives in order to prevent the build-up of deposits (typically, on [[fuel injector]] and [[intake valve]]) known to reduce fuel economy and engine performance.<ref>{{Cite web
| url = http://www.toptiergas.com/deposit_control.html
| title = Deposit Control Standards
| access-date = 2012-10-19
| archive-url = https://web.archive.org/web/20040806012056/http://www.toptiergas.com/deposit_control.html
| url-status = dead
| archive-date = 2004-08-06
}}</ref>