You just can't have enough oil threads. I posted this in the other forum and decided to do it here too in case some don't go to it.
My 2012 Base with a manual transmission has a little over 19k miles on it.
I let the factory fill go to 3619 miles and had the dealership change it because they gave me one free oil change. I have always done routine maintenance on all of my cars, but I thought since it was free, I may as well let them do it. The was done in January 2012. I bought the car on October of 2011. At the time the dealership was using conventional 5-30 Shell. I wasn't crazy about them using 5-30 when the oil cap said 5-20.
I left that oil in until April of 2012. The car had 7260 miles on it at the time, so the oil had 3641 miles on it. I decided to use Pennzoil Platinum(PP) 5-20 as I have used it in a 2004 Mazda 3 HB I used to own and in a 2006 Honda Element that I still have. I have been able to get 7500 miles or so out of it on those vehicles before it starts looking like it needs to be changed. I'm too cheap to send off a sample to Blackstone. I've read plenty of oil analysis on the BobIsTheOilGuy site. On the Soul I noticed around 3500 miles that the oil had a little gas smell to it and was pretty dark. I never noticed this while using the same oil in the other cars.
I decided that if the car was going to be that hard on oil that I wasn't going to pay for synthetic. So at 10,864 I went back to the Kia dealer and had them change it again. They only charge $8.88 for an oil change (when conventional 5-30 is used). The total cost is about $15.50 after tax and fees. So the Pennzoil Platinum had 3604 miles on it when I dumped it.
I kept that oil in until 15,326, so it had 4462 miles on it. It wasn't as dark as the Pennzoil Platinum that had about 800 less miles on it. I thought maybe the PP had better cleaning additives in it and I should try it again, so I did.
I changed it again yesterday at 19,235 when the oil had 3909 miles on it. It was smelling like gas again, was dark and appeared to have lost its viscosity. I decided to go back to the dealer to do the $8.88 oil change again. When I got there, they said they can no longer do that on KIAs. KIA is making them use 5-20 now - probably due to the fuel mileage issue. This dealership uses a semi-synthetic 5-20 and the cost of the oil change with tax and fees would have been over $34. I can do a full synthetic change for that price, so I passed.
I did buy a filter and drain plug washer while I was there for $8 and change. I went across the street to Wal-Mart to get the oil. I always buy oil from them as they are MUCH cheaper than anywhere else. I could get a five quart bottle of PP for $26, where at Pep Boys or AutoZone it was about $8 or 9/qt. As much as I hate Wal-Mart, I'm not going to spend $40 or $45 on oil elsewhere when I can get it for $26 from them. I could have got conventional Pennzoil (aka PYB on BITOG) for about $14 for the 5 quart bottle or Quaker State for about a buck less. I decided to get Motorcraft 5-20 Semi-Synthetic for about $18. About five years ago this oil was around $11. Oh well. It does get great reviews on BITOG. I'll see how long it lasts.
I'm not sure why I get the gas smell in the oil. I got 36.7 mpg two tanks ago and 34.5 on the last one. I have never got less than 30 and it is usually in the 32 to 34 range. I calculate this myself. The car's mpg calculation is always 1 or 2 mpg high. Given the mpg I am getting, I don't think the engine is using excess fuel. I think it has to do with the GDI engine. Most people own the 2.0 liter version of this engine, where I have the 1.6. Maybe there is a difference between the two. I don't have any confidence in going over 4000 miles between oil changes the way it is now.