First up we need to set things straight, Kia is an exceptional brand that produces a high quality vehicle for a very fair and reasonable price. Like all vehicle they require you to keep on top of the maintenance of them, unfortunately Kia and in particular the Carnival and Grand carnival are less forgiving than other makes and models if you neglect the maintenance of the vehicle.
The fault in question is the fact that the Kia V6 engine fitted to many year models of the Carnival and Grand Carnival can develop a smoky problem. After a few skipped services and then receiving a oil change the Kia develops a lot of white smoke out the exhaust pipe. This is often worse on a cold start up.
The Lack of oil changes has caused the engine to sludge up, which has caused rubber seals to harden and in some cases the oil scrapping piston ring to stop doing its job. After receiving a service and a fresh dose of oil the Carnival is now pumping smoke out the back and you naturally assume you mechanic has done you some sort of dis service. The facts are that because of the lack of oil changes the engine internals are now damaged and the fresh new oil is making its way into the combustion chamber and then out the exhaust.
The correct rectification procedure for this is to firstly diagnose if the fault is caused by valve stem seals or if it is in fact the piston rings that need replacing. Either way this is a large and labour intensive job which will hurt your pocket.
One alternative which is only a band aid fix is to use a thicker grade of oil and an additive called stop smoke. This additive is as thick as molasses and more than likely is doing damage to other engine components that require good oil flow to them. We have seen clients successfully reduce the smoke by using a 20W50 grade oil and the stop smoke additive. We do not advise this as a permanent fix but it will reduce the smoke while you save a few pay checks to get the fault rectified.
It is worth noting that when first released the Kia Carnival had many recalls for piston ring faults. It may be worth having a discussion with your local Kia dealership if you have developed this issue and have kept to the services. If you have missed your services you have little chance of getting help form the dealer.
Kia does offer 7 years warranty so if you have this issue and you have been religious with your servicing Kia may come to the party and help you if you are still within the seven year window. You can find information on this by clicking the link below.
Kia and the seven Year warranty.
Finally the Kia service manual advises that the service intervals for this vehicle is 15,000kms or six months. Which ever comes first. We agree with six months but strongly feel that 15,000kms on any car is far to long between drinks. Most consumers are looking at kms rather than months anyway and 15,000 on any engine, let alone one that is common for oil consumption faults, is not frequent enough. if you own a Kia of any sort we advise every 5000kms for an oil change.