So... are sludged engines a thing of the past?

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I was just thinking about this the other day during the 47 threads on T/GDI fuel dilution of the engine oil. It seems to be, at least to some extent, that these engines should never suffer being sludged to death, right? I mean, if they are truly dumping 3, 5, 9% volume of gasoline into the engine oil, and gasoline is obviously a solvent, is it even possible for an engine to form sludge with that much solvent in it?

Obviously there are the other concerns of fuel in the oil causing lubrication problems, which, at least to me, seem to be mostly unfounded since we are not having engines fail left and right after they've put up a 3-5% fuel content on their UOA. So I'm lead to believe that a majority of the fearmongering of fuel in engine oil is just that, and with today's oils and add packs, a low-level fuel intrusion does not have a negative effect on lubrication, and may also keep engine oil from sludging? Just a thought...
 
It was my understanding that with GDI, the fuel burns more completely creating more power, better MPG, and fewer emissions. It also caused issues with carbon on the valves because you are not getting fuel wash over the valves to keep them clean. If this is indeed the case, where does the fuel dilution come from?
 
I ran a carbed Jeep until '11. Reading UOA for oil from a GDI is scary compared to a UOA from a non-GDI. The fuel contamination has to go waaay down before, I'd consider a GDI
 
No sludge can still be an issue if oil is not changed regularly. I have seen Kia forum posts of sludge problems with GDI. I believe that these were on the 2.4 engine.
 
Originally Posted By: otis24
It was my understanding that with GDI, the fuel burns more completely creating more power, better MPG, and fewer emissions. It also caused issues with carbon on the valves because you are not getting fuel wash over the valves to keep them clean. If this is indeed the case, where does the fuel dilution come from?


From what I understand:

1) With a cold engine, fuel injected directly into the cylinder, especially if the injector is at an angle, fuel can condense on the cold cylinder wall and get past the rings

2) Compared to a port-injected engine the fuel has less time to fully evaporate before combustion occurs, leaving some unburned droplets that again can get past the rings

3) DI gives engineers a whole new toolbox to deal with issues like spark knock. Instead of retarding timing when it’s detected as was the case with port injection, the mixture can be richened instead, again leaving more unburned droplets. This seems to be why using premium fuel reduces dilution in some DI engines.

4) To prevent LSPI, OEMs program DI/TGDI engines to inject additional fuel at any throttle/rpm combination that might cause it, again creating more unburned droplets. SN Plus oils may allow some of this intervention to be avoided, but we’re not there quite yet.

Despite all of this, DI engines do seem to have a fuel economy and performance advantage, but it’s still a maturing technology.

Additions/clarifications welcome.
 
This seems to have turned into a GDI vs non GDI thread, different from the OP’s question.

I think we will not see the sludge issues going forward like we saw in the past in general. Sure there will be some extreme cases. Opening valve covers to see sludge right up to the gasket level is extreme. Today’s oils are better.
 
Originally Posted By: Virtus_Probi
Maybe GDI engine makers should advertise that they are giving owners a free petroleum-based solvent flush with every oil change?
;^)
`

All for the low price of $89.99, shop fees may be extra ;-) .
 
Originally Posted By: JLTD
IMO if your oil is taken far enough past its condemnation point, you will get sludge.


OK since you opened this door, I want to shove you through it.

Define your understanding of condemnation point. Doug Hillary posited on here it was when the oil gets to 150ppm of Fe. For my engine, that's roughly somewhere between 145-155 THOUSAND miles on the same oil, and that's not diluting it any with makeup oil. About the only engines I have seen that can hit the 150ppm limit in any kind of reasonable OCI are likely Gen 1 SBCs, these seem to shed 7-10ppm of Fe per 1k miles. Even the "OMG it's got fuel dilution!!" 3.5 EB motors only make around 3ppm/1k, so that would mean they can go 50k miles per OCI?

Again I reiterate my point/comparison- most "engine flushes" are around 12-16 ounces. This will usually equate to 8-10% of the sump volume. If your GDI engine is putting 3-5% gasoline in the oil, this is essentially the same as half a bottle of engine flush, over the whole OCI. Just positing questions here... I'm not in the market for a T/GDI anytime soon.
 
Just did a timing belt and valve adjustment on an MDX with 160k km and the front head was sludged to [censored]. Vehicle only saw oil changes as per maintenance minder.
 
Originally Posted By: SubieRubyRoo
Originally Posted By: JLTD
IMO if your oil is taken far enough past its condemnation point, you will get sludge.


OK since you opened this door, I want to shove you through it.

Define your understanding of condemnation point. Doug Hillary posited on here it was when the oil gets to 150ppm of Fe. For my engine, that's roughly somewhere between 145-155 THOUSAND miles on the same oil, and that's not diluting it any with makeup oil. About the only engines I have seen that can hit the 150ppm limit in any kind of reasonable OCI are likely Gen 1 SBCs, these seem to shed 7-10ppm of Fe per 1k miles. Even the "OMG it's got fuel dilution!!" 3.5 EB motors only make around 3ppm/1k, so that would mean they can go 50k miles per OCI?

Again I reiterate my point/comparison- most "engine flushes" are around 12-16 ounces. This will usually equate to 8-10% of the sump volume. If your GDI engine is putting 3-5% gasoline in the oil, this is essentially the same as half a bottle of engine flush, over the whole OCI. Just positing questions here... I'm not in the market for a T/GDI anytime soon.

You can't assume the Fe contamination rate is linear forever though. The rate seems to be linear while the oil is still "good" but at some point the oil won't be able to minimize wear any more, and contamination, sludging and wear will go exponential.
Off the top of my head I think I've seen totally sludged engines with 30k-40k on the oil, and I don't think extreme fuel dilution will help much.
 
Originally Posted By: mightymousetech
Just did a timing belt and valve adjustment on an MDX with 160k km and the front head was sludged to [censored]. Vehicle only saw oil changes as per maintenance minder.


Interesting.
 
Originally Posted By: mightymousetech
Just did a timing belt and valve adjustment on an MDX with 160k km and the front head was sludged to [censored]. Vehicle only saw oil changes as per maintenance minder.


VCM engine?
 
Originally Posted By: SubieRubyRoo
Originally Posted By: JLTD
IMO if your oil is taken far enough past its condemnation point, you will get sludge.


OK since you opened this door, I want to shove you through it.

Define your understanding of condemnation point. Doug Hillary posited on here it was when the oil gets to 150ppm of Fe. For my engine, that's roughly somewhere between 145-155 THOUSAND miles on the same oil, and that's not diluting it any with makeup oil. About the only engines I have seen that can hit the 150ppm limit in any kind of reasonable OCI are likely Gen 1 SBCs, these seem to shed 7-10ppm of Fe per 1k miles. Even the "OMG it's got fuel dilution!!" 3.5 EB motors only make around 3ppm/1k, so that would mean they can go 50k miles per OCI?

Again I reiterate my point/comparison- most "engine flushes" are around 12-16 ounces. This will usually equate to 8-10% of the sump volume. If your GDI engine is putting 3-5% gasoline in the oil, this is essentially the same as half a bottle of engine flush, over the whole OCI. Just positing questions here... I'm not in the market for a T/GDI anytime soon.


You're not shoving me anywhere, and you can stop trying to paint me into a corner. If you don't understand my meaning, then read the site so you will understand the meaning of the phrase, "condemnation point". And also so you might understand that condemnation point may be subject to interpretation, aka debated BITOG style, depending on who you're talking to, what they drive, and their driving habits.
 
Originally Posted By: mightymousetech
Just did a timing belt and valve adjustment on an MDX with 160k km and the front head was sludged to [censored]. Vehicle only saw oil changes as per maintenance minder.


VCM?
 
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