Thought some of you in here might like this:

Hey guys there has been a bunch different threads on oil, especialy on oil life - ie: changing frequency. One of my concerns is I have a couple cars I do not drive very often, so they do not get many miles put on them and I am not sure how long (timewise) I can wait between changes. So I emailed Royal Purple with afew questions and they got right back to me. Just wanted to share it with you. My questions are followed by their answers:
1) Do you recommend a particular oil filter?

You are welcome to use the filter of your choice, as we do not have one we fell is better than others. Some of us here use Wix, [/b]NAPA[/b] Gold, K&N, Mobil 1, or OEM filter[/b]

2) Which viscosity do you recommend? My vehicles manufacturer recommends 5w30 but I live in Arizona where it is very hot and I have always used 10w30.

You can use either RP 5w30 or RP 10w30. Your radiator will keep your car cool, and our oil will also help reduce the operating temperature of your vehicle.[/b]

3) I see you recommend up to 12 months between changes. One of my cars I use very seldom and maybe put 500 miles/ year on it. If I start the vehicle on a regular basis to bring it up to operating temperature to combat moisture forming inside the engine can I extend the time between changes?

Since you do not drive you car that often you can go 2 -3 years with a filter change and oil top off every year before you store the car. We do not recommend starting the car unless you plan to drive it. Starting and bringing the car to temp. does not mean the oil is at a high enough temperature to burn off any moisture or fuel that could be in the oil. If you start the car you should drive the car, to avoid adding to the moisture, which is a by-product of combustion. It is safer to let the car sit for 3months then it would be to start it every month.[/b]
[/b]
Here is our recommendation for how often you should change your oil in your other cars-[/b]

How often should I change Royal Purple in my passenger car? [/b]
[ul][/ul]
Royal Purple recommends following the manufacturer’s maintenance intervals while the vehicle is under factory warranty. In clean engines that are no longer under warranty, oil change intervals may be extended up to every 12,000 miles or annually, whichever comes first. Oil filter changes should be done as recommended by the filter's manufacturer and oil should be topped off as needed.
In dirty engines, Royal Purple recommends the standard 3,000 to 5,000 mile oil and filter change interval until the engine oiling system is clean and free of deposits left by lower quality oils and / or poor maintenance or mechanical problems. This will allow time to gradually remove existing deposits without overloading the oiling system. Mechanical problems such as fuel dilution, coolant leaks into the crankcase, poor air filtration and / or failure to maintain proper oil level are all detrimental factors to the service life of any engine oil. Any one of these factors can significantly shorten the useful service life of any oil.

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