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On my Honda, whenever the maintenance minder says too, which is about every 6K miles.

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Full synthetic, every 10k.

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Used Oil Analysis' at Bob Is The Oil Guy BITOG.com

http://www.bobistheoilguy.com/forums/ubbthreads.php/forums/3/1/Used_Oil_Analysis_-_Gasoline



NoVaRight, you are half right.  UOA's are useful for a number of reasons. Most people use them to check the oil condition, but they also use them to check the engine condition.  One shows the other.  

UOAs show wear metals (rings, cylinders, cam lobes, etc) as well as anti-freeze, water, and fuel amounts in the oil. People get UOAs to see whether there are any bad things going on with their engine.

Also shown in the UOAs are oil life indicators.  TBN (total base number, how much acid-eating additives are left), insolubles (dirt/carbon particles), and viscosity (high or low) show the condition of the oil itself. Oil can fail in several ways. It becomes too viscous, or too thin. It can contain too much dirt or carbon (filter failure, too). Most consider the main failure point to be when the TBN goes below 1. At that point it can no longer counter the effects of acids that develop and is no longer protecting in that way.

But by and large I think users get them done because THEY ARE ANAL about their car and oil. Anality manifests itself in a number of ways with cars and oil. The 3k mile change is one. Buying the best oil and filter available (or are perceived to be the best) and changing way before the oil needs it is yet another.  Both, however, depend on substituting money for knowledge. The user is throwing money away in lieu of knowing actually what is going on.  By using UOAs to check the engine and oil health, the user is seeing what is going on and can plan accordingly.

One does not need to buy UOAs at each oil change.  A user can get one done on the first one to see that there are no catastrophic failures right from the factory. They can get another done after a few more oil changes to see if anything has developed over the short term. Then they could get one at any point thereafter, as they see fit.  Or, they could get it done at EVERY oil change as a hobby.  There are a lot of hobbies that cost waaaaay more, so talking bad about the buyers of such things is pretty useless.

But the overall question is when to change oil.  The answer is, after you learn about oil, and come up with a number, THAT's the right interval for you.  But for my money, 5k mile intervals w/Mobil1, oil weight dependent upon the vehicle.

BTW, I remember an old web page that is no longer available that tested oil  and filter life on a '98-ish Z28.  The results were amazing and went HARD against the grain of conventional thought. The website took a UOA every certain interval and checked all the numbers.  The oil (Mobil 1 5w-30) protected out to about 16k miles IIRC.  Filters lasted approx. 10k miles. It was amazing to see it all happen.  It completely blew apart the 3k mile interval thing, a holdover from non-detergent oils of the past, and gave rise to the 10k mile intervals of today.  Still, I can't bring myself to leave oil in that long so I change at 5k miles.



YMMV.



http://www.briggsauto.com/blog/wp-content/uploads/2013/11/oil-sludge-engine-1024x768.jpg













 

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It blows me away what people spend on Royal Purple when M1 0W-40 is about $25/5 quarts at Walmart.  

And it is unlikely that M1 0W-40 will be "too thick" for whatever you drive.

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6.0 Superduty

Oil - 5k
Fuel Filter every 15k

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(my vehicle is a 2009 Toyota Tacoma 4.0L V6)





I've been running Royal Purple 5W-30 synthetic oil and Bosch "Distance Plus" filters since I got the truck new.  I change the oil every ~4000 miles (when the light comes on).  Last night at Pep Boys when I plunked down like 60+ bucks for oil and filter I was like God dang, this is *ridiculously* expensive for a do-it-yourself oil change.  It actually would have been more if I didn't already have a quart or two of oil left from the last change.  





So I started to wonder if I can go longer between changes with such a high end oil and filter.  Maybe as high as 10,000 miles?  





The way I figure, if I'm not going to extend the life out of the oil and filter, what is the point in using such high dollar stuff in the first place, what am I really getting out of it?





Commends/thoughts welcome!  





I also wonder if Pep Boys is really the right place to be buying that stuff, but nonetheless, it's extremely expensive for what it is.

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4k-5k miles.  Any longer and and the engine runs noticibly more rough.  That's also when the oil starts to appear dirty so changing it seems like a good idea.

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Every 5 k. Easy to remember on odometer

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Full synthetic, every 10k.