I found the link that I mentioned above. Great information on lubes. It all started from a newspaper article about "Pickup Truck Records One Million Miles on PennzoilŪ Motor Oil". I started using Castrol GTX when I was 15 (good father), then I switched to using Synthetic (Castrol Syntec or Mobil 1), now after reading this article I'm looking for a new Synthetic oil to use for my next oil change.

Pickup Truck Records One Million Miles on PennzoilŪ Motor Oil

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Thanks,
Dave

1998 BMW 540i Sport
1995 E320
1992 400E
1989 BMW M3
1979 Triumph TR7 (1st car)
1986 BMW 735i (Sold)
1980 BMW 320i (Sold)

Recently, Mobile oil changed the formulation of the popular Delvac 15W-40 diesel oil. It was using a Group II base stock as Chevron Delo 400 15W-40. Now it uses a mixture of Group II and Group I base stocks. Remember that Group II base stocks are more refined than Group I and has less wax and other impurities.

The link below is from the Mobile Website and it explains why a cheaper base stock is better for your car:

http://www.mobil.com/mobil_lubes/onhighway/products_services/delvac1300/faqs_content.html

Here are some quotes from them:

The new formulation incorporates a mixture of high viscosity index Group II and low volatility Group I base stocks that feature superior performance in heavy-duty engine oil applications. These new base stocks, manufactured using proprietary ExxonMobil technology, are uniquely coupled with progressive additive chemistry to further enhance the position of Mobil Delvac 1300 Super 15W-40 as the industry's technological leader.

It is likely you will notice that the oil is darker than the previous formulation. Although oil color is simply a physical property, our deeper color is being largely driven by chemistry changes that deliver stronger performance.

Through this forum, I have developed a compulsive behaviour to change oil and filter frequently and religiously. And changed when oil has been run in for at least 15 km.

I use semi-syn and without additives.

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... Kerry

126 tailed by a 203, 129 leading the pack.