What does oil have to do with DI engines?

[otis24]

I was a salesman at a GM dealership when Direct Injection engines were coming on market and GM began the push for Dexos approved oils. I had also been a long time member of BITOG, so I was aware of reports of engine sludge and other problems with DI engines. I asked the GM trainer about this and his response is that that was why the Dexos oil requirements. Based on my rudimentary understanding of how engines work, what do oils have to do with Direct Injection? Oils do not enter the combustion chamber, at least not in sufficient quantity to provide a detergent effect. What am I missing?

 

[AZjeff]

Originally Posted By: otis24
What am I missing?


PCV

 

[Artem]

Well, Dexos oil can be formulated to withstand say, fuel dilution from Di engines better then oil B. That's about as far as the story goes.

 

[Quattro Pete]

LSPI?

Also...
http://www.underhoodservice.com/oil-direct-fuel-injection/

 

[bigj_16]

LSPI

 

[AZjeff]

Low Speed Pre-Ignition is mainly a problem in turbo engines isn't it?

 

[Quattro Pete]

Originally Posted By: AZjeff
Low Speed Pre-Ignition is mainly a problem in turbo engines isn't it?

Yes, but a lot of GM's DI engines are turbocharged, so it applies to OP.

 

[UncleDave]

The part you are missing is that the (expensive) high pressure direct injection pump has a tremendous load on it - similar to a diesel HEUI type oil pressure driven pump.

This load is typically driven off a tertiary lobe on a cam.

This extreme pressure shears and is hard on oil.

UD

 

[SilverSnake]

Originally Posted By: Quattro Pete
LSPI? Also...http://www.underhoodservice.com/oil-direct-fuel-injection/


Excellent article. Thank you.

 

[StevieC]

LSPI, Fuel Dilution as I understand it.