Oil changes fulfill the same function for these GDI (gasoline direct injection) engines as they do for other “normal” gasoline and diesel engines. Used oil gets drained and does so (hopefully) per a healthy interval that yields good value (service life relative to cost, and good engine protection throughout) and gets that oil out before it experiences significant changes in lubricity and additive protection. Oil filters get changed because they have a finite amount of capacity to store debris that gets removed from the engine oil, and if they are run for too long, excessive debris storage can result in the filter going into bypass.
GDI engines need oil changes for the same reasons that other engines do, but they can actually degrade the oil’s performance more rapidly. This is relevant to both oil selection and proper change intervals. Also relevant to oil selection is the concern of LSPI (low speed pre-ignition). This condition commonly occurs in GDI engines and can be prevented or discouraged by running engine oil that resists LSPI activity. Unfortunately, while GDI (gasoline direction injection) represents an advance in technology, it’s an advance that the North American oil market has not fully caught up with.
Soot production is a normal characteristic of GDI engine operation. The problem that can occur here is that soot production suspends hard particles in the engine oil. These particles have been associated with timing chain wear. Two of the most important ways to counter this are to change the oil before soot production has the chance to encourage chain wear, and to run (if possible) oil of the ideal dynamic viscosity (this goes beyond simply selecting oil based on the viscosity printed on the bottle.)
GDI engines with poor oil change history (or less than ideal oil change history) risk premature timing chain wear (please see “Soot Production” above.. Timing chain replacement is a major repair operation. The cost to do it well is certainly far from engine rebuild or replacement territory but also substantial enough that you want to keep that timing chain setup healthy for as long as you possibly can. Time will tell with GDI engines, but previous (older technology) fuel injected engines have commonly seen chains last for 200,000 miles and much longer still!
An easy way to think about this is that GDI engines “beat up” on the oil more quickly than the “normal” fuel injected engines that have been around for 20 years now. Maintenance schedules don’t always reflect this and may show the same minimum and maximum intervals for both engine types. So (for example), for a “normal” gasoline engine and a GDI engine being run under similar conditions, if 5,000 miles is a appropriate interval for the “normal” engine, we might advocate 4,000 miles for the GDI engine. This goes back to the concern of warranty period versus desired vehicle lifespan. The vehicle probably won’t need much extra help to get through the warranty, but if you want that engine to last for a 300k life cycle, careful oil change interval selection might help you!
LSPI refers to low speed pre-ignition. This is a condition in which uncontrolled combustion occurs in the engine’s cylinders or combustion chambers. Uncontrolled combustion refers to a condition in which out of control combustion events take place (at the wrong time, wrong location in the cylinder, or both). Severe uncontrolled combustion can cause internal damage (Further details available in separate entry.) There are engine oils available that discourage this activity from taking place.
GDI engines are harder on the engine oil than the preceding fuel-injected engines that have been around for the last 20 years or so. Extra attention to oil selection, a little bit more money for high-grade oils, and moderate reductions in common change intervals can help you save money over the long run.
A5/B5, API SP, and LSPI protection are relevant things to look for in oil selection.