A semi or tractor trailer can hold up to 40 quarts of oil after you drain the old oil out.
So when you change oil in a semi or tractor trailer you need to be sure you have at least 40 quarts of oil so that you have enough oil to fill the oil pan of the semi.
Semi trucks or tractor trailers take a lot more oil than a regular pickup truck or car.
I once saw a guy in Walmart buying 40 quarts of oil and he said he had a Semi Truck that he was changing the oil in.
I didn't think those semi trucks took that much oil but I learned something new.
I'm glad my vehicle doesn't need that much oil.
That can equate to around 5 to 10 gallons of oil for a semi.