Hi Sean

"Proper" or "Blended" brands

Most of the "Proper" brands are blended anyway

We use the Vauxhall Trade Club 10w40 and 5w30 after years of expensive Valvoline, Castrol oils etc

I did enquire with Vauxhall for data sheets for the two oils before i would commit myself, the e-mail back from Vauxhall was enlightening

The 5w30 is a synthetic longlife oil and is supplied by FUCHS, they sell the same oil under their own banner

The 10w40 is a semi synthetic and supplied by MORRIS, one of the oldest and most established oil companies in the world. Morris also supply base/stock oils to larger "Branded" companies so they can blend their own

So don't be put off by the low price of the Trade Club oils, GM would not supply inferior quality oils. The "Branded" and "Motor Factor" reps will tell you otherwise, but that's just sour grapes because they cannot compete on price

Peter

PS: Been using the GM oils for 2 years on mostly late vehicles with no problems....we purchase 205 ltr drums