TooSlick,
I think you misread some items:
"If the vehicle manufacturer recommends drain intervals of 7500 miles/1 year under "normal conditions" - as does Toyota - then you should be able to run even an average quality, "SL" rated petroleum oil this long. I would certainly consider 90% highway driving @ 75 mph to be almost ideal in terms of oil degradation, wouldn't you?"
Mola: First of all, I didn't say that you couldn't run over 3.5k, I only stated that oil analysis should take place at 3.5k and not later in order to avoid oil related suprises. I do not agree you can run an oil this long simply because it is "spected" to do so. I consider field tests and endurance runs to be indicitive of service, not just engineering data alone. It takes engineering data AND field tests to work out bugs.
"Toyota has been pushing to get the even better, GF-4 oils on the market ASAP, according to Lubricants World magazine. Why do you think that is?"
Mola: I think it is because Toyota, as well as other vehicle makers, wants to extend drain intervals, reduce maintenance cost, and get as much CAFE as possible out of their engines.
"If you can't run this 7500 drain interval under ideal conditions, then the engine design is defective - period. That is why Toyota has agreed to settle this issue out of court and extend the warranty on these 3.3 million affected engines to 8 years with unlimited
mileage - provided you can show the oil has been changed at least every 7500 miles."
Mola: No, I think Toyota screwed-up in a number of areas rushing to advertise this engine as their highest power density V-6 widget, just as Amsoil screwed-up with their XL7500 formulations. Had Toyota tested their engines and oil past 7k this problem would have reared its ugly head. Had Amsoil tested their their claims in this V-6, they would have not kept up their 25k prayer meetin's. The owner took Amsoil at heart, believing that the oil would go 25k miles. As I have stated in other posts, I believe both Amsoil and Toyota should have shared the costs of engine replacement in this specific case.
"I would not be surprised to see Nissan go the same route on their 2.4L if they start having oil related engine failures. Designing a pickup truck engine that is used to carry heavy loads this way is simply poor engineering. Of all people, you should certainly understand that .... "
Mola: The oil companies, including the specialty blenders, should have realized long ago that engine power densities have gone way up past some of their oil's capabilities
and not guaranty oils that cannot be expected to perform past 7k in these environments.
As a matter of fact, Nisssan recommends 3.7k oil changes for the Frontier. BTW, NISSAN DID NOT SAY THAT AMSOIL IS AN EXCEPTION TO THIS RULE.
[ November 19, 2002, 02:28 PM: Message edited by: MolaKule ]