4 Litre Cans Of Oil

Plannng to do my first oil filter change on the Thunderbird. The book says (?) that you need 4.2 litres of oil. Have folk found this right? Why does the recommended oil (Castrol) only come in 4 litre containers, meaning you have to pay the extra for a 1 litre container to filI up on oil change. I know this sounds moaney but whatever happened to 5 litre containers - fill up your bike & use the rest of the oil during the year to top up.

 

Sorted then, will go for that brand and size. Thanks.
Cynically I wonder why Triumph recommend a brand when the biggest container doesn't fill the bike.

 

Thanking you for the link. I did have a gander before but only came across 4 litre containers - my conspiracy feelings were in overdrive!