http://neptune.spacebears.com/cars/stories/mobil1.html Very interesting reading!! Turns out it works BETTER over time Some original photos have not been recovered yet.

Yes maybe, but.............. The oil itself is probably o/k but what about contamination from combustion products and metal wear particles? They suggest frequent filter changes and leaving the same oil in there. Also, in cold weather acids produced from the hydrogen in the fuel may not be removed by the PCV if you only do short trips and the engine temperature is below optimum most of the time. The cost of many oil filters might actually end up costing you more than if you just change the oil regularly. At least with new oil you know it is completely clean. When Mobil one first came out, they advertised widely claiming you could leave it in there for 50,000 Km. They ended up being sued by unhappy owners for engine damage, and it cost them a bundle. Mobil no longer make claims about how long it will last. Funny that.

You'd really need to do the same kind of testing out here with our kind of weather (0�C to 40�C instead of -30�C to +30�C), our kind of oil to suit (5W50 instead of the much thinner 5W30) and our kind of engines (non-oil blowing turbo six rather than sludgy V8 with a lot of wear/manufacturing problems by the looks. Oil top up between changes ? What's that ?) to get a proper look at the picture. You'd also perhaps need to look at perhaps three vehicles, one driven normally in the city, one country driven and one driven once a week but flogged on the street/drag strip. As all our engines are so old now I don't think you'd ever get anything like reliable results from such a test. Speaking as someone who's car has been on the stuff since 15,000km (now 270,000km) with changes every 5,000 I've got nothing but good things to say about it and I just love the polished metal look inside when you pop the filler cap off. Some original photos have not been recovered yet.