Firm believer in that Amsoil. Great oil, super grease.
We have been taking oil samples on some trucks down here for awhile.
Everytime we think about changing the oil, send in samples, remarks come back
telling us to run it another 7,000 - 10,000 miles and take another sample.
One truck has 17,000 miles on that oil, and they say keep running it. ( Ford 7.3 diesel )
Chevy Duramax has approx 16,500 miles on that oil, and the Dodge Cummings, has bumping 14,800 on that engine oil.
We changed the Amsoil EA filter right at 14,000 miles, they guarantee the filters
to 15,000 to 25,000 miles.
We have several others, including gas burners. They don't have the miles on thier oil like the diesels, but we send samples out to them also. We use the Oil Analyzers Inc. and the
Blackstone Industries companies for samples. Blackstone sends there sample bottles free.
They give you the Source of Elements in your oil, iron , lead, copper, zinc, Titanium, silver, nickle, etc,... etc ....
.... and , the oil degradation such as soot, oxidation nitration, acid, etc ... etc .>>
Will let you know the physical properties as water, anti-freeze, fuel, Vidscosity, and any solid contaminants that made its way into your oil .....