I noticed that it seemed off as well so I lookes it up. The character is sometimes is pronounced shen and sometimes can but in this context can seems correct.

When I hover over the words, I can see that 加 is add while 油 is oil!

Here's some extra knowledge about the two characters if you are interested:

加 is made of 力 and 口. 力 means "power/ strength" while 口 is mouth as you may know. The original meaning of 加 is the exaggeration of speech, and you can guess that from the constituents - "to use strength when your mouth is open". It acquired the meaning of "increase" because when you exaggerate something, then the nature of that thing may be boasted. Hence, the word also refers to add, as add is similar to increase.

油 is made up of the 3 dots on the left which represents water, and 由 on the right. 由 in ancient hieroglyphics was actually a drop of liquid falling onto a bowl (try to imagine), which people later referred to as a bowl with oil. As the meaning of oil transformed, people added 3 dots on the left to show that oil is a liquid.

Some funny, extra knowledge. If you see the word 加油添醋, it is no longer "add oil" = "come on". It means "add oil and add vinegar", as an idiom to describe how a person exaggerates things by adding a lot of made-up content. E.g. 他喜歡在說話時加油添醋的！