Plug-in hybrid electric vehicles with its low local emissions are very promising alternative to conventional vehicles. Similar to conventional hybrid vehicles, plug-in hybrid electric vehicles use multiple energy sources for propulsive power. The power split between these energy sources must be managed carefully to achieve reduction in fuel consumption and carbon dioxide emissions. The decision to use either or both of the power sources is made by the vehicle supervisory controller. Depending on how the supervisory controller uses the off-board electricity source, supervisory control strategies can significantly impact the component size, cost and overall vehicle energy efficiency.This paper reports the impact of supervisory control strategies on a full parallel plug-in hybrid electric vehicle's emission performance over two drive cycles. The effects of a limiting speed for electric only driving and carbon dioxide emission under various vehicle operating modes are investigated and reported. The paper also discusses the benefit of light weighting of city cars and its impact on green house gas emissions. It has been shown in this paper that well-to-wheel carbon dioxide emissions less than 50 g/km is possible in real world applications using light weight PHEVs.