DI engines: ethanol fuel better?

[Benzadmiral]

In several items I've read on the 'Net, many of which are over my head technically, I've seen the occasional suggestion that use of ethanol-charged gasoline could help with the tendency of DI engines to buildup deposits on their intake valves. Now as I understand DI, no gasoline "washes" the valves, unlike in port-injected engines. So I don't see how E10 gas can help with the deposit problem. Or am I getting this backwards?

Is there any accepted preventative for these deposits, other than frequent oil changes with a low-NOACK, carmaker-approved oil?

 

[Quattro Pete]

Originally Posted By: Benzadmiral
Is there any accepted preventative for these deposits, other than frequent oil changes with a low-NOACK, carmaker-approved oil?

In some cases, driving aggressively now and then seems to help - high sustained temperatures apparently help burn off some of the deposits.

 

[Swift101]

I use top tier gas and drive aggressively on occasion.

A little redline for a good time

Time will tell if it cleans out deposits.

 

[badtlc]

Originally Posted By: Benzadmiral


Is there any accepted preventative for these deposits, other than frequent oil changes with a low-NOACK, carmaker-approved oil?


Yes, keeping the RPMs above 4500 for 20+min every now and again to help prevent and clean.

Prevention is aided with regular injector cleaning, running premium oil and not changing the oil too often.

 

[Benzadmiral]

Originally Posted By: badtlc
Originally Posted By: Benzadmiral


Is there any accepted preventative for these deposits, other than frequent oil changes with a low-NOACK, carmaker-approved oil?


Yes, keeping the RPMs above 4500 for 20+min every now and again to help prevent and clean.

Prevention is aided with regular injector cleaning, running premium oil and not changing the oil too often.

Hm. This seems counter to all BITOGer wisdom I've read on the subject. Why would it help to not change the oil often? Does fresh oil contribute, in the early weeks after a change, to more deposits? Or does oil that's run longer deposit less oily film?

 

[Hyde244]

On the topic of E10, you are going to be using it regardless as majority of America has E10 at the pumps.

Driving the engine at higher speeds can help burn off deposits, and keep a well maintained OCI schedule also helps ensure deposits are minimal.

 

[Benzadmiral]

Well, there are still a few non-ethanol gas stations in my area; I'm hanging on to the pure stuff, and avoiding the ethanol blend, as long as possible.

The local Buick dealer says they recommend changing their dexos1 approved oil, AC Delco semi-synthetic, at 5000 miles, never mind the OLM. I'll follow that regimen, or maybe 4500 miles, even when I go to synthetic.

And it'll take an effort for me to run my car at 4500 rpm for 20 minutes straight. Hard to get over the feeling that I'm throwing gasoline, and thus money, out the window.

 

[sciphi]

The theory of not changing the oil too often (Warning: Opinion following!!!) revolves around how older oil usually has had the more volatile stuff gone out of it early on. Thus there isn't as much stuff passing through the PCV system, and less to deposit onto the intake valves. At least that's my take on why that theory works. Gosh knows if it's correct.

Otherwise, I'd run a synthetic to help combat fuel dilution, and otherwise have less stuff the PCV system needs to deal with.

I may be talking out my derriere, but an in-tank PEA cleaner still might be able to do some good if enough PEA can survive the oil to travel through the PCV system and ultimately make it onto the valves. That's just my uninformed rambling, take it as you will.

 

[Hyde244]

Originally Posted By: Benzadmiral
And it'll take an effort for me to run my car at 4500 rpm for 20 minutes straight. Hard to get over the feeling that I'm throwing gasoline, and thus money, out the window.
Highway driving will more than suffice; a 70 mph cruise in the 2,500/3,000 rpm range.

 

[wemay]

Originally Posted By: Swift101
I use top tier gas and drive aggressively on occasion.

A little redline for a good time

Time will tell if it cleans out deposits.


My method as well.

 

[Benzadmiral]

Originally Posted By: Hyde244
Originally Posted By: Benzadmiral
And it'll take an effort for me to run my car at 4500 rpm for 20 minutes straight. Hard to get over the feeling that I'm throwing gasoline, and thus money, out the window.
Highway driving will more than suffice; a 70 mph cruise in the 2,500/3,000 rpm range.

I've got a long road trip into Texas coming up in 2 weeks. Plenty of opportunity for that!

 

[wemay]

Also, there is a theory that the only way to combat dilution is thru more conservative oci, not extended ones. Be it with conventional or synthetic oil, no difference.

 

[Garak]

Originally Posted By: Benzadmiral
Hm. This seems counter to all BITOGer wisdom I've read on the subject. Why would it help to not change the oil often?

This has been posited by one of our most respected members some time ago, but the jury was still out on that one, and presumably still is.

 

[Shannow]

Originally Posted By: Quattro Pete
Originally Posted By: Benzadmiral
Is there any accepted preventative for these deposits, other than frequent oil changes with a low-NOACK, carmaker-approved oil?

In some cases, driving aggressively now and then seems to help - high sustained temperatures apparently help burn off some of the deposits.


My take is less that the temperatures are high enough to burn off deposits, than break them off...

e.g. when the metals run hotter, they expand. The deposits have a different co-efficient of thermal expansion, and can only handle a certain amount of internal shear forces.

Once that's exceeded, they flake off, or only ever form to their shear limit.

Could be mildly uncomfortable if a Granny car is given an Italian tuneup, but I've had engines swallow stellite exhaust seats without being wrecked, so probably no biggie.

edit:...forgot to add that this was what I was theorising back in the days of water washing...water cannot dissolve them, it has to break them off...

 

[tstep]

http://crcindustries.com/auto/intake-valve-cleaner.php

Anyone ever try CRC intake valve cleaner?

 

[Lurgi]

tstep,
Thank you for that link! I've been looking for a product like that from a well respected company like CRC for years! I didn't know it existed.
I've already signed up for my $5 rebate and will be reporting my results on a direct injected car with 77k miles that has become low-octane intolerant.
Thanks again.

 

[Hyde244]

Originally Posted By: Benzadmiral
Originally Posted By: Hyde244
Originally Posted By: Benzadmiral
And it'll take an effort for me to run my car at 4500 rpm for 20 minutes straight. Hard to get over the feeling that I'm throwing gasoline, and thus money, out the window.
Highway driving will more than suffice; a 70 mph cruise in the 2,500/3,000 rpm range.

I've got a long road trip into Texas coming up in 2 weeks. Plenty of opportunity for that!
Perfect! Will definitely help with deposit control.

 

[TiredTrucker]

I have been convinced for some time, that no matter the design, there is always some oil, condensation, etc making its way thru the PCV line to the intake manifold. If you get on any number of the performance car forums, and several truck forums, installing a PCV oil catch can is the cat's meow for keeping the stuff from making it to the intake and building up on intake valves and increasing deposits in the combustion chamber. Also, oil and other particulate in the combustion chamber can lower the overall octane rating of the fuel in the burn. This is known from performance engines.

I installed on on my 2013 5.3L and in roughly 10,000 miles, it captured about 1/2 quart of oil and gunk that would have made it to the intake. In that 10,000 mile interval, the engine used a total of about 2/3 quart of oil.

I am convinced that the first line of defense with a DI engine is keeping any crankcase residues and particulates from getting to the intake. A PCV oil separator catch can would do more than anything else as a proactive measure. It would greatly reduce the intake deposits and reduce the risks of lowering octane in the combustion chamber and knock.

 

[Lurgi]

And to the other posters,
I'm having problems with a direct injection car pinging on low octane fuel. I ran top tier gas exclusively since the car was new (almost 3 years ago.)
Top tier didn't do anything. I recently started running premium to prevent the knock sensor from causing ignition retard and thus waste of fuel. The car went from a max of 37 mpg to 42.5 mpg. The premium fuel is actually cheaper to run the car on with this massive improvement in economy.
I suspect intake valve deposits and or piston crown and combustion chamber buildup.
Once again, top tier gas has not prevented this problem from developing. As evidence, the car didn't ping at all when it was new. And it didn't get 42.5 mpg either when new. A design or production flaw? I don't know.

 

[Shannow]

auto-ignition is a problem with the GDI cars, and GM/API are working on oils to prevent it.

If you've got oil, and only oil in the end-gasses, near the walls, they can be much more prone to dieseling that when there's fuel mixed with it as well.

There's some papers around that I've linked to before on GDI oil formulation to reduce end gas autoignition.