Okay, well I'd suggest you add column headers to the first two columns, say "Category" and "Fuel". Then export it as csv. We don't want the title, so if you can select specifically what to export, just don't select the first two rows. If you can't do that before the export, then just delete the first two lines of the resulting file. What we want is a file that looks like this (just showing a few lines):

Category,Fuel,2018,2019,2020,2021 Combines vehicles,Petrol,1964,1735,1523,1406 ,Diesel,14904,13044,11506,10316 ,Paraffin,0,0,0,0

We don't really need the first column either, but it'll work either way.

Now we need to import as a Dataset (replace pathToFile with the actual path):

theData = Import[pathToFile, "Dataset", HeaderLines -> 1]

You should now have a Dataset. Now do the totalling:

theData[GroupBy["Fuel"], Total, {"2019", "2020"}]

For simplicity, let's say your dataset looks like this:

origData =
 Dataset[
  {<|"Thing" -> "A", "Type" -> "4 cyl", "2019" -> 1, "2020" -> 4|>,
   <|"Type" -> "6 cyl", "2019" -> 1, "2020" -> 2|>,
   <|"Thing" -> "B", "Type" -> "4 cyl", "2019" -> 3, "2020" -> 4|>,
   <|"Type" -> "6 cyl", "2019" -> 0, "2020" -> 2|>,
   <|"Thing" -> "C", "Type" -> "4 cyl", "2019" -> 2, "2020" -> 3|>,
   <|"Type" -> "6 cyl", "2019" -> 6, "2020" -> 4|>}]

Then maybe you want something like this:

origData[GroupBy["Type"], Total][All, {"2019", "2020"}]

Thanks for the reply Eric, however, it's difficult to carry out this operation on the dataset I have because it's not an association list. I tried to convert the lists of list to an association but the repeated row names it isn't making it any easier.

Hi Eric, I've attached the excel file. Thanks.

Attachments:

Data.xlsx