Originally Posted by catchmeifucan
Well, I would agree that you should be able to extend the life of your oil to at least 7,500 miles with your highway driving.
But, one thing to consider - the warranty (GM and Extended)
I had a Ford car that had just went out of the factory warranty. And, I had purchased a extended warranty through Ford. At about 40K, the lifters starting tapping. Ford essentially refused to cover the engine work because I could not demonstrate that I had changed the oil per their recommendations.
So, since the GTO has a sensor (is this truly a sensor or just mileage driven anyway?), I would assume the mileage in between would extend out with this highway mileage. I would just take it to a local dealership and have them change the oil as needed. This way you should get the extra miles between changes and they can't argue about meeting their recommendations and that the job was done by their own trained mechanics.
I would prefer to change my own oil myself. But, after this experience with Ford, I will continue to pay a few extra dollars have the dealership change the oil until that warranty expires.
This sounds strange but I remembered reading about When to Change Engine Oil (GM Oil Life System) a few weeks ago and it mentioned in the GTO owners manual about not pertaining to mileage of the engine but being based on other factors. So I just now got out the owners manual again so as to read that section. I opened the manual to 5-16 and this is a quote from the 04 GTO Owners Manual as follows: Your vehicle has a computer system that lets you know when to change the engine oil and filter. This is based on engine revolutions and engine temperature, and not on mileage. Based on driving conditions, the mileage at which an oil change will be indicated can vary considerably. For the oil life system to work properly, you must reset the system every time the oil is changed.
When the system has calculated that oil life has been diminished, it will indicate that an oil change is necessary. A Service Engine Oil message will come on. Change your oil as soon as possible withen the next two times you stop for fuel. It is possible that, if you are driving under the best of conditions, the oil life system may not indicate that an oil change is necessary for over a year. However, your engine oil and filter must be changed at least once a year and at this time the system must be reset.
Then it goes on about what to do after having reset the system accidentally. Incidentally, the next page 5-17 How to Reset the Service Engine Oil Message, tells you how to reset the (GM Oil Life System) with your accelerator pedal.
Myself, I will make the first oil change with filter at 2,000 miles which is a few miles away. Then it will depend on when the oil Life system comes on or if I get uncomfortable with the mileage before it comes on. Somewhere on one of these forums I seen an owner who has 8,000 miles on his GTO and has no oil change light come as yet!!! If I was him I would take it in for oil and filter change and have the system checked out. Never know if there could be a failure in the warning system. Hope this helps!!!