Originally Posted By: CrackyWainwright
Well you fellows have scared me off of doing the M1 AP and one year OCI in the 2.4 KIA. I hadn't purchased the oil and M1 filter when I first made the original post, so I guess I'll go back to my normal habit of Castrol EP and a Fram Ultra for ~12,000 miles.
Question: Can someone explain to me (I'm not a mechanic) what's DIRECT INJECTION and why it's hard on oil in an engine such as the KIA 2.4? Thanks.
Traditional port fuel injection injects fuel into the intake manifold where it mixes with air and is inhaled into the combustion chamber. Direct injection injects the fuel directly into the combustion chamber.
The advantages of direct injection are improved fuel economy, more power and more manageable emissions because:
1) The fuel evaporates in the combustion chamber the associated cooling effect occurs there rather than in the intake manifold. This cooler charge allows a higher compression ratio that in turn has fuel economy and power benefits.
2) Direct injection allows more precise timing and metering of injected fuel (sometimes making multiple injections of fuel per stroke), also helping with power, fuel economy and emissions.
The disadvanatages of DI are:
1) Because the fuel/air mixture doesn't wash over the intake valves, carbon deposits can build up as PCV vapors hit the hot valve. This problem seems to have been largely addressed by OEMs, but the worry persists.
2) Despite the overall fuel economy improvement, DI allows largish droplets of fuel to remain unburied, part of which will make their way past the piston rings and wind up diluting the oil in the sump and reducing the oil's viscosity. This is the primary worry with your Kia, as Kia/Hyundai, Honda and some Ford EcoBoost engines seem to be chronic fuel dilution offenders.
3) While not a worry in the US yet, DI engines also have more particulates in their exhaust. Eventually, DI engines may be required to include a particulate filter like diesels.
Fuel dilution is hard to deal with. The only strategies that seem to work are:
1) More frequent oil changes
2) Heavier viscosity oil to compensate for expected dilution
3) Top-tier fuel, perhaps in a higher-than-required octane
4) Avoiding short-tripping, especially in cold weather