Fellas, thank you for all the great advice in my previous thread on same; I'm in Austin TX for the moment...a local AMSOIL dealer who owns a diesel eng shop in Austin said that AMSOIL also recommends their 5W30; this guy loves it; said it improved mileage and pressure. My owner's manual says 15W40 for the temperatures of south Alabama. My truck is a 2001 GMC 3500 Duramax w/ 53K miles.

Can I trust this 5W30 AMSOIL?

--Bryant

 

I'm not aware of any problems using it. It's highly recommended by AMSOIL as it's their most "robust" diesel oil, but I myself am a little gun shy. I like the 40 weight. It does help with fuel mileage. Same principal behind why all these OEM's are changing from 5W-30 to 5W-20 oils...fuel mileage only.

 

I wasn't aware of a 5-30 diesel oil. I'm still unsure about changing to 5-40 oil

 

The 5W30 is great for those who mainly use their trucks as daily drivers. I know two individuals myself that switched to the 5W30 and are reporting increased fuel mileage. If you're doing any heavy towing and live in an extreme climate like Texas, New Mexico or Arizona I'm not so sure I would trust it to protect my $15K engine. For the record, I run Amsoil in everything I own so I'm not speaking against the Amsoil product but the 5W30 oils in general.