The objective of this study is to examine the determinants of household petrol and diesel expenditures using a large micro data set of Irish households. This research is timely given the switch in purchases from petrol cars to diesel cars arising out of changes in how vehicle registration tax and motor tax rates are calculated. The study finds that households living in urban areas, households that spend money on public transport and households that do not possess a car will spend less on both petrol and diesel. In contrast, households in possession of higher number of cars, households with more occupants working and households with higher levels of household spending will spend more on petrol and diesel. The econometric methodology employed takes into account the fact that the dependent variable contains zero expenditures. Such an approach has never previously been applied to analyse Irish household transport use and provides interesting insights. In particular the effect that the explanatory variables have on participation in the market is quite different for petrol and diesel. For example, the model predicts a much larger increase in the probability that households will spend in the diesel market relative to the petrol market as income increases. The results have implications for the design of tax policy in the transport sector as the Irish economy recovers and average household income increases.