Yeah, I’d rather be there to be honest. But the car culture is admittedly pretty cool here. Tons of supercars too.
Alrighty. No worries.
So you have the Amsoil European Formula 5w40 Classic Formula which, as I found out, is rated for Diesels. I’m surprised, I didn’t know about this one; it doesn’t show up under Amsoil’s “Diesel Oils” section (oh, dear.) I’m guessing it’s not fit for all Diesel Engines. You got a break with it, here’s why:
As far as Viscosity goes (and hence, fuel economy,) this 5w40 is more of a 0w40. I’m even more surprised, I didn’t realize there were any Amsoil Diesel Oils in the xw40 range that are this thin:
Kinematic Viscosity @ 100°C, cSt (ASTM D445) - 13.6
Kinematic Viscosity @ 40°C, cSt (ASTM D445) - 83.3
To compare, Renewable Lubricants’ Low Ash 5w40 is:
Kinematic Viscosity @ 100°C, cSt (ASTM D445) - 14.0
Kinematic Viscosity @ 40°C, cSt (ASTM D445) - 76.9
Huh. I wasn’t expecting this, either; between these two oils, although the Amsoil 5w40 that you have in your car now is thinner when hot, RLI’s oil is thinner when cold.
In short, I think the Amsoil 5w40 you have in your car now is about as fuel efficient as you can get it without sacrificing engine longevity; Shell T6 0w40 (yes, it exists; please don’t mistake it for 5w40) is thinner, but I don’t expect it to give near as much protection to the engine. Here are its viscosity ratings:
Kinematic Viscosity @ 100°C, cSt (ASTM D445) - 13.2
Kinematic Viscosity @ 40°C, cSt (ASTM D445) - 75
I won’t talk about engine longevity based on oil at the moment, I think I’ve covered enough for now.
Sources:
Amsoil European Formula 5w40 Data Sheet (4 different oils are listed here, your oil is listed as “EFM.”)
Renewable Lubricants 5w40 Low Ash Data Sheet
Shell T6 0w40
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