Octane, Ethanol, and Dilution

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I bought a 2018 Hyundai Elantra Sport a couple of weeks ago, and have been zipping around in it.

Got about 900 miles on it now.

Checked the oil today, smells like a fuel factory.

I have been putting 90 octane, ethanol-free Valero (a recommended Top-Tier branded) gasoline in it.


Does octane and/or ethanol levels play any role in dilution, or are they unrelated?

What steps can be taken to mitigate dilution?


The reason I like the higher octane and the ethanol free is supposedly they help prevent LSPI.
 
Reduce short trips if possible. Is the 90 the highest octane available?

I also short trip the Mazda but I purposely drive the long way when I can. Run the car at highway speeds for 30+ minutes each week if possible. The last thing to do is to keep oci short.
 
In your manual, you have the option of 3 oil weights. 5w20, 5w30, and 10w30 all in the chart on page 8-9. Since you smell fuel, and its a DI engine, and the manual allows it, i would run a 5w 30 oil. The fuel is already reducing the viscosity of the 5w20 to even less.

You could get a uoa sample drawn after a typical drive, and send it of to confirm fuel ( i'm going to do this on my mazda). A 5w 30 oil will give you a bit more viscosity if you are getting fuel dilution.
 
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being in a warmer area the 10W-30 is a better choice, less viscosity improvers and a better noack, prolly a higher HTHS as well that is seldom shown anymore. noack and hths are important and not easily 'pumped' up by additives that do not last.
 
Unless it is very well known synthetic (Mobil, Motul, etc.) the XW rating mostly tells you what the base oils are. 5W is thinner than 10W in base oils. Then they add VII's to make the op temp (hot) grade numbers.

Fuel dilution thins the base oils badly, so given any choice, always opt for the highest XW grade they will allow. In this case it's 10W-XX.

Don't put expensive oil in there as you'll have to run short oil change intervals. The only effective solution for fuel dilution is change the oil ... Sorry, but it's a fact of some cars life. It used to be bad carburetors, now it DI engines. We're back to 3~5,000 mile oil changes.

Use a good quality oil with chemistry that will reduce intake deposits, but no need for expensive synthetics as you are not going to get their real benefit before the oil has to come out ...
frown.gif
 
FYI, not that it has anything to do with your situation. The 90 octane E0 may not be the same brand as the station.
 
Originally Posted By: BrocLuno


Don't put expensive oil in there as you'll have to run short oil change intervals. The only effective solution for fuel dilution is change the oil ... Sorry, but it's a fact of some cars life. It used to be bad carburetors, now it DI engines. We're back to 3~5,000 mile oil changes.


OCI, OCI, OCI is most important when combating dilution, nothing else.
 
Just stay with the pure fuel and 5w30 full synthetic oil. Clean throttle body with CRC GDi IVD cleaner. iTs made for DI and has PEA in it every 10k. Use Gumout Regane/Redline Si-1 in conjunction. No Seafoam. No PEA,no good.
 
Go with the octane rating as specified in your owners manual. If it's regular then using a premium will have no benefit. The octane rating is commensurate with your normal combustion chamber temps. Going with a higher octane when not required could lead to more unburned fuel.
 
Originally Posted By: wemay
OCI, OCI, OCI is most important when combating dilution, nothing else.


What's the typical OCI called out by manufacturers for their DI engines? If fuel dilution is a major concern I'd think the OCI would be less than a typical non-DI vehicle calls out.
 
Originally Posted By: ZeeOSix
Originally Posted By: wemay
OCI, OCI, OCI is most important when combating dilution, nothing else.


What's the typical OCI called out by manufacturers for their DI engines? If fuel dilution is a major concern I'd think the OCI would be less than a typical non-DI vehicle calls out.


My normally aspirated GDi?
Normal: 7500 /12 months
Severe: 3750 /6 months*

The turbo GDi?
Normal: 5000 /6months
Severe: 3000 /same*

*me
 
So wemay, you could say it is the turbo that changes the OCI recommendation, NOT the fact that they are GDI.

Based on many EcoBoost UOAs, I think the whole fuel dilution thing is WAY overblown on here. I can't remember seeing ANY UOA that was truly concerning solely due to excessive fuel. Maybe now that we're moving to ultra-low sulfur fuels it's nowhere near the issue it once may have been? I know gasoline is not a lubricant... but it also has a much, much lower viscosity and therefore would be "pushed away" by the oil?

I'm not saying try to run 20k OCIs on a GDI, but I think a large portion of the witch hunt is just that, until I see horrible UOAs or failed GDI engines that had reasonable UOAs. JMO
 
Some distillation curves




Premium should have less left in the crankcase both with or without ethanol.
 
I agree with SUBYRUBYROO THAT fuel dilution in most cases is overblown because, the wear values are usually low or in-line with non DI engines. A teas-spoon of gasoline in a gallon of oil smells like 50% fuel due to the aromatics in gasoline. I guess BITOGers need something to champion. Ed
 
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Originally Posted By: SubieRubyRoo
So wemay, you could say it is the turbo that changes the OCI recommendation, NOT the fact that they are GDI.

Based on many EcoBoost UOAs, I think the whole fuel dilution thing is WAY overblown on here. I can't remember seeing ANY UOA that was truly concerning solely due to excessive fuel. Maybe now that we're moving to ultra-low sulfur fuels it's nowhere near the issue it once may have been? I know gasoline is not a lubricant... but it also has a much, much lower viscosity and therefore would be "pushed away" by the oil?

I'm not saying try to run 20k OCIs on a GDI, but I think a large portion of the witch hunt is just that, until I see horrible UOAs or failed GDI engines that had reasonable UOAs. JMO


My earlier UOA for the 2.4 non-turbo did show a little "trace" dilution, the most recent ones have shown slightly less (not that i do a lot of UOA). But i do drive under the "severe service" schedule so change out accordingly. For those who don't care to UOA, my suggestion remains to shorten your OCI. Regardless of turbo, GDi will dilute is driving under certain conditions.
 
I would definitely stick with a very reasonable 5000 mile oil change. Also make sure you only use high-end ice OEM filter. You have to remember these cars have a really lousy track record for destroying their own engines. Take a look at the Hyundai forums and you’ll see exactly what I mean. For some reason it appears to affect cars in very cold climates to a far greater degree whatever that means. Of course Hyundai having solved the problem a couple of times in the past many years seems to keep having the problem so don’t count on much help from them. All this mess started with sonatas with that direct injection engine 2.4 and 2.2 but it’s now happening to the Elantras as well.
Also do keep your receipts and such when you do your oil changes just in case you’re one of the unlucky ones like my daughter who had the engine begin to die at 45,000 miles. All OEM filters all top-tier synthetic done by me personally so I know when I speak of here. The previous solution to the Hyundai Electra problem with some new sort of coating on the Pistons in 2014 which sure didn’t work as we found out with her 2015 . If I was you I would take the cell phone and record a nice long clip of how your engine sounds running now and save it so you’ll have something to compare to if you think you hear the dreaded ticking. it starts like a slightly loose valve and then just progresses in our case coming from over by the timing chain top section. Also from others experience watch out for it suddenly using a lot of oil. That never happened in our case however it didn’t burn a drop.
Anyways sorry to rain on your parade but these are just things I keep an eye on with any DI Hyundai with that Theta 2 mill. They have been pretty good from what I read at replacing engines but I have to say in our experience the engine they put in sure didn’t sound like the original. It sounded more like my old farm all tractor and the daughter said it didn’t seem to have the power so we get rid of it pronto, hello Toyota . Sign up for the Hyundai Forums. That’ll make it easier for you to keep up with who is ruining what how well they’re being treated. Good luck with yours..........
 
Originally Posted By: Eddie
I agree with SUBYRUBYROO THAT fuel dilution in most cases is overblown because, the wear values are usually low or in-line with non DI engines. A teas-spoon of gasoline in a gallon of oil smells like 50% fuel due to the aromatics in gasoline. I guess BITOGers need something to champion. Ed


+1

It doesn't take much fuel in the oil to smell it and unfortunately, I think people here tend to say "it's diluting like crazy" if they can smell it at all. My small displacement DI car will have a fuel smell in the oil in relatively short order but it doesn't get worse over a 5K OCI. No issues in five years of having the car. I think it just comes with the territory.
 
Engine is new. you will have more fuel smell given a turbo, Di, and new engine.

Even I run 10w30 QSUD to keep my NA port injected 2.5 Nissan running proper.

I don't think a turbo, high compression and Di would like a 20 or a severe multigrade.
 
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Originally Posted By: Vuflanovsky
Originally Posted By: Eddie
I agree with SUBYRUBYROO THAT fuel dilution in most cases is overblown because, the wear values are usually low or in-line with non DI engines. A teas-spoon of gasoline in a gallon of oil smells like 50% fuel due to the aromatics in gasoline. I guess BITOGers need something to champion. Ed


+1

It doesn't take much fuel in the oil to smell it and unfortunately, I think people here tend to say "it's diluting like crazy" if they can smell it at all. My small displacement DI car will have a fuel smell in the oil in relatively short order but it doesn't get worse over a 5K OCI. No issues in five years of having the car. I think it just comes with the territory.




Thanks for putting scientific reason to this. I too check by smell but I’m used to oil not smelling like gasoline. A gas chromatography test for fuel dilution would be the ideal test rather than the nose.

Also, I have noticed as well that uoa’s done on severely fuel diluted fuel samples have shown low wear rates. The only thing I might question is a long term effect of FD as I don’t know of any members here with 100k plus miles showing high FD all along the way.
 
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