SAE 40 for warmer climates?

[MissTrish]

A friend who has had long experience of Gardners recommended using Shell Gadinia 40 for southern France where we both have our boats. Summer temperatures are around 30 - 35 degrees. However spring temperatures are often not very different to uk. I've followed this advice for the last 3 years with no problems, but I am feeling slightly uneasy since said friend's big end recently failed on his 6LW.

According to my manual SAE 40 is OK down to 10 degrees, while the upper limit for SAE 30 (from memory) is 30 degrees. I believe multigrades are not favoured for older engines.

I'd be grateful for readers' thoughts about this and whether I should change oils.

 

Jon

Zee Otter

[jonesthenuke]

I have a manual which states below 2C SAE 20, 2-32C SAE30 and over 32C SAE40.

 

I do not have a date for this manual but in one place it refers to a 1967 British Standard, so must be later than that date. I have a 1945 manual but it dies not give SAE values.