The hydrocarbon emissions results for the bio-diesels are shown in Fig. 10. It can be seen that bio-diesel A and B show an increase in hydrocarbon emissions with increasing blend ratio. Conversely, the US EPA reports that HC should decrease with increasing blend ratio. Fig. 11 shows that HC emissions of bio-diesel A increased by 1% while bio-diesel B increased by 80%. This is quite different compared to the US EPA figures which suggest that HC emissions should decrease by around 65%. If diesel/bio-diesel hydrocarbons were to be measured accurately, a flame ionisation detector would need to be used instead of the infra-red (IR) sensor that was used for this testing, but this equipment was unavailable.