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72c20customcamper · 06-05-2023, 03:59 PM

Been using it for a while I buy big containers since I have two diesels . It does have less zinc than it used to Since diesels have cats on them too for the past years . But to be honest I’ve never had an oil related issue in 30 years of driving old flat tappet engines . 15-40 is more than thick enough

The 15 is when it gets to 30 degrees so it will flow like a 15 weight oil the 40 means it will still retain the viscosity of a 40 weight oil when hot . Don’t think you need to worry about the cold number .

This is a good oil for warm climates Castrol GTX Classic and at $24 for 5 quarts it’s a good deal

https://www.amazon.com/Castrol-Class...5995518&sr=8-2

06-05-2023, 03:59 PM	#3
72c20customcamper Registered User Join Date: Jul 2018 Location: Catskill Mountains,NY Posts: 8,225	Re: Question about oil viscosity Been using it for a while I buy big containers since I have two diesels . It does have less zinc than it used to Since diesels have cats on them too for the past years . But to be honest I’ve never had an oil related issue in 30 years of driving old flat tappet engines . 15-40 is more than thick enough The 15 is when it gets to 30 degrees so it will flow like a 15 weight oil the 40 means it will still retain the viscosity of a 40 weight oil when hot . Don’t think you need to worry about the cold number . This is a good oil for warm climates Castrol GTX Classic and at $24 for 5 quarts it’s a good deal https://www.amazon.com/Castrol-Class...5995518&sr=8-2 Attached Images __________________ Mark 72 c20 custom camper Husky edition, 66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark 1969 AMX , 1968 c20 stepside ,85 K20 1977 Suburban sold 68 anniversary. Last edited by 72c20customcamper; 06-05-2023 at 04:08 PM.