Three light-duty vehicles were measured on-board for their fuel
consumption and regulated emissions while driven on diesel, pure
rapeseed plant oil (PPO) and a 5% biodiesel (B5) mix with diesel.
They were driven along a realistic cycle covering urban, rural and
motorway roads. The vehicles were an Opel Vivaro 1.9 DTI Van, a
Citroën Berlingo 2.0 HDI car and a Nissan Patrol GR 3.0 diesel SUV.
Each vehicle was retrofitted with an Econet PPO two tank kit. They
started on diesel when cold and switched to PPO -heated over a heat
exchanger- when warm.
As PPO has a lower caloric value compared to diesel fuel,
consumption on PPO was higher. On B5 no significant effect was
noticed. PPO however has lower carbon content and CO₂ emissions
were a few percent lower than on diesel except for the Nissan
Patrol where they were 8% higher. Carbon monoxide (CO) emissions
were low on all fuels and showed no clear trend except for the
Nissan Patrol that emitted three times more on PPO and for the Opel
that emitted three times more on B5. The total hydrocarbon (THC)
emissions were two to three times higher on PPO but at a very low
absolute level. Nitrogen oxide (NOx) emissions were higher on PPO,
from 9 to 56%. On B5 there was no significant effect. As to the
Particulate Matter (PM) emissions a drop of about 50 to 60% was
found. On B5 there was a drop of less than 10%.
The Nissan Patrol in this study showed high CO emissions at
idling when running on PPO. The engine management system was not
able to correct this and produced a fault code indicating that the
fuel was out of specification. Overall this vehicle was having
higher fuel consumption and emissions on PPO than the other two
vehicles. This indicates that not every diesel-fuelled vehicle can
be easily converted to PPO with success.