I read a few places that they say with Mobile 1 synthetic oil that you can go up to 15,000 miles before changing it. I would do maybe 5-6,000 at the most. Going 15k or a whole year would have a sludge built up, right?

 

Yes. It's doable but a bad idea.

 

My Toyota goes 10k using 0w20 Mobil. Factory recommends it.

 

I just sold my 2012 MBZ C250 (1.8 L turbo) to get my Sonata Sport 2.0T and I was suprised that Hyundai requires 5,000 mile oil changes even with synthetic oil. My 2012 MBZ C250 was 10,000 miles using Mobil 1 per factory spects and the newer MBZ are now at 15,000 miles for oil changes using Mobil 1.



Before the MBZ I had a 2010 Infiniti G37s bougjht new and it was 7,500 miles for oil changes using synthetic oil and that was back in 2010.



Unfortunatly unless the factory changes their reccommendation it is 5,000 miles to maintain warranty, but everyone else is at 7,500 -15,000 miles per service

 

My F150 uses an oil life monitor. Usually goes about 8K miles.

 

5K is probably for "severe duty" a.k.a. city driving on cheap oil. Any good synthetic with an OEM filter and you'll be fine for 8k-10k if you keep it topped off. With a premium synthetic oil and regular used oil analyses to keep an eye on it, and with keeping an eye out for sludging, 15k is not out of the question.

 

Stick with Factory recommendations and you'll be fine and save money on less expensive oil! Only newer engines with much tighter tolerances can really take advantage of longer change intervals. Ring gaps and piston to wall clearances are so much smaller on a new engine so you get much less contaminants in the oil to cause it to break down sooner. Stuff big enough to be caught by the filter don't break down the fluid, its the combustion blow by that does.