GT-40 Oil

[Canuck-Surfer]

So up here in Canada, I compared what's been mentioned here. SAE40 in almost non-existant in stores. VR1 20W-50 and Royal Purple (type ??) are available but crazy expensive ($35/qt). Shell Rotella T4 Diesel 15W40 is easily available and dirt cheap.... $26/gal $62/5 gallon bucket from Walmart. So I am leaning towards the T4. Rebuilt GT40 engine is about to get dropped back into our 96 Sport so I want to have a plan from get-go.

Only question I have is how cold mornings in August impact the 15W-40. It can often be 8 C (45 F) airtemp for morning surf runs (water is still warm...70 F). Is the 15W-40 good in those conditions since I can't source straight 40 easily?

[GMLIII]

So up here in Canada, I compared what's been mentioned here. SAE40 in almost non-existant in stores. VR1 20W-50 and Royal Purple (type ??) are available but crazy expensive ($35/qt). Shell Rotella T4 Diesel 15W40 is easily available and dirt cheap.... $26/gal $62/5 gallon bucket from Walmart. So I am leaning towards the T4. Rebuilt GT40 engine is about to get dropped back into our 96 Sport so I want to have a plan from get-go.

Only question I have is how cold mornings in August impact the 15W-40. It can often be 8 C (45 F) airtemp for morning surf runs (water is still warm...70 F). Is the 15W-40 good in those conditions since I can't source straight 40 easily?

I had no problem getting the cheap house brand of straight 40 oil for my GT 40. Ran it with no problem for 16 years and over 1,000 engine houses. It should be ready available even in Canada

[windsurfnut]

So up here in Canada, I compared what's been mentioned here. SAE40 in almost non-existant in stores. VR1 20W-50 and Royal Purple (type ??) are available but crazy expensive ($35/qt). Shell Rotella T4 Diesel 15W40 is easily available and dirt cheap.... $26/gal $62/5 gallon bucket from Walmart. So I am leaning towards the T4. Rebuilt GT40 engine is about to get dropped back into our 96 Sport so I want to have a plan from get-go.

Only question I have is how cold mornings in August impact the 15W-40. It can often be 8 C (45 F) airtemp for morning surf runs (water is still warm...70 F). Is the 15W-40 good in those conditions since I can't source straight 40 easily?

I'm also in Ontario. Been running Rotella T4 15W-40 for years now in my GT-40 Ski Nautique and my big block 502 MAG Baja 232. We ski/boat early in the season (soon as the ice goes out) and well into the fall. Highly recommend the Rotella T4 15W40- my GT 40 oil was pristine at the end of our high hour ski season each year.