I remember in the 1960s - 1980s where carbureted cars, especially during colder months, had huge fuel dilution issues. I ran everything from 5w30, 10w30 to 10w40 and didn’t give it a second thought. 3-4K OCI’s. Can anyone point to a study or UOA on newer DI cars where damage has been caused by Fuel Dilution? It seems to me that the manufacturer’s have done their homework and so have the oil companies for newer cars. Fuel Dilution, even when raising the oil level, has no detrimental effect on engine wear. Am I wrong???
Fuel dilution is nothing new
- Thread starter Oliveoil2
- Start date
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You are not on the wrong train of thought
What causes bearings to spin?
Back in the 60's a 100K miles on a car was a pretty decent run. Today it's a walk in the park for most cars. Simply put yea oil got better, so did fuel management with the invention of EFI. Some of us might say DI could have been considered a step backwards in some instances, especially early DI. Flame suit on.
Yes that is correct, carbed engines also suffer from it especially on cold start, then with the adoption of multipoint port fuel injection that problem was for the most part eliminated.
Now with GDi engines, yeah they may make more power and be more efficient, but i don't want one, the issues with fuel dilution and intake deposits is somethimg that has yet to be solved if there is any way to solve it other than more frequent oil changes and periodically having to manually de-coke the intakes .
All in all i think too that the cons of GDi outweigh the pros, and that port fuel injection is overall the best.
Now with GDi engines, yeah they may make more power and be more efficient, but i don't want one, the issues with fuel dilution and intake deposits is somethimg that has yet to be solved if there is any way to solve it other than more frequent oil changes and periodically having to manually de-coke the intakes .
All in all i think too that the cons of GDi outweigh the pros, and that port fuel injection is overall the best.
I was just going to type this!
A car that made 100K miles was rare. And usually a guy using the lousy oil back then changing it every 2K or less!
Engines sludged up with regularity, and hard black junk too.
I think some memories are just being selective. We had a couple beasts that poured gas in the oil. Not pretty.
Our age is showing!
But nowaday's oil is much better, i myself have a 51 year old engine, never bewn rebuilt just the heads, knocking on 240k miles now, cross hatching still present in the cylinders, British Ford Essex 3.0 V6, Weber 38/38 carb.
Run on mostly 20W-50 conventional or 10W-40 most of its life.
Run on mostly 20W-50 conventional or 10W-40 most of its life.
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A few thoughts.
We ran much thicker oil back then
We changed the oil more frequently back then.
The big one - engines were often oil burners at 100K back then.
I do remember dilution back then, but it was mostly due to cars that were flooding or had a sticking choke at startup. Remember back then the car atomized the fuel way, way upstream from the cylinder back then. The issue wasn't dilution as much as running rich and fouling plugs and valves.
We ran much thicker oil back then
We changed the oil more frequently back then.
The big one - engines were often oil burners at 100K back then.
I do remember dilution back then, but it was mostly due to cars that were flooding or had a sticking choke at startup. Remember back then the car atomized the fuel way, way upstream from the cylinder back then. The issue wasn't dilution as much as running rich and fouling plugs and valves.
There is a lot of UOAs that show dilution didn't do anything.
However, once the dilution gets too extreme I think we do see wear. In these UOAs we start to see lead.
Mobil 1 1.9k miles / 2020 48k miles Rav4 - Fuel Dilution
Hello all, Looking for advice. Here is the only UOA I’ve done on my wife’s 2020 rav 4. We purchased it with around 30k miles on it. I started to notice an alarming rise in the oil level (smelled fuel-like), decided to dump and get a sample. I estimated an additional 1/4 - 1/2 qt of fuel. I...
bobistheoilguy.com
2018 CRV 40.1k mi // M1 EP HM 5W30 1.6k mi - Fuel Dilution Bonanza!
Okay. Let me preface this. I intentionally did an OCI for the four coldest months of the year (11/17 - 3/17), where fuel dilution is at its worst. I *expected* astronomically high fuel dilution. My theory is, if I can bottle up the worst of the fuel dilution in the coldest months of the...
bobistheoilguy.com
Another thought I have been having lately around the fuel dilution topic is maybe some of these port fuel injected engines were having some fuel dilution but we just weren't seeing it. Like we all know how inaccurate Blackstone's method of determining fuel dilution is. During the era of mostly port fuel injection, UOA on this site were mostly from Blackstone. Now we know how inaccurate they are, so maybe we were getting some fuel dilution without knowing. So wonder if we were using someone that used GC for fuel dilution measurement, we might be more accustomed to some fuel dilution.
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Possibly - but the reason dillution has become more discussed is not because of blackstone, but because many peoples garages started to smell like gas stations - people that would never likely changed their own oil in the past let along analyzed it. Its always certain models - like the Honda 1.5 seems to be one of the worst, but GDI only turbo engines in general seem to be the main ones.
A lot of people are actually attributing it to the oil not getting warm enough / thermal efficiency - which might also be true.
Unless you tore down the engine, and measured bearing clearance, you had no idea if wear was taking place.
The absence of catastrophic failure is not the same as “no detrimental effect”
Patman
Staff member
I have always used Wearcheck for my UOAs and they do a proper GC for fuel dilution and in the 9 or 10 cars that I have taken samples for, I have only had a couple of instances where I have seen high dilution. One was on my 2006 Civic when I had a leaky injector and saw 7% fuel dilution (which I brought down to zero on subsequent UOAs after using a lot of good PEA injector cleaners) and the other time was on my Corvette on it's very first UOA of the factory fill where it showed 2% dilution (which came down to zero on subsequent UOAs) The Corvette is the only direct injected car that I've taken samples for, all others were port injected.
In my train of through, I was thinking we would be more accustom to fuel % in the 1-3% range instead of blackstones <0.5% or 0%. Like for example, my wife's car which in theory shouldn't have fuel dilution because its a naturally aspirated port fuel injected engine (Honda R18 in a Civic). But my last UOA done by Oil Analyzers on the car showed 3.5% fuel. So, it appears on some engines, where one would expect a fuel dulition result of basically zero, can have some fuel dilution. We will see what the result it when I change the oil again.
As has been noted a UOA is not the tool for determining the totality of issues regarding fuel dilution. Besides increased wear from viscosity loss, there are other detrimental effects of fuel that will not be seen in a simple spectrograph analysis. Increased oxidation is one thing along with detrimental effects on dispersants and other additives.
I'm not sure why such unwarranted importance is placed on these $30 UOA when many of the posters have been involved in lengthy discussions about their limitations. There is not one good thing about fuel diluted oil nor is it benign.
Carb vs PI and DI. Remember, PI and DI also run a much richer mixture when cold, but, much better controlled.
Patman
Staff member
You should try what I did in my R18 Civic and run a few bottles of a good PEA fuel system cleaner through it, because after I did that in mine the fuel dilution went down to zero. So her car might possibly have a leaky injector too. Does it ever take a few extra cranks to fire up when it's sitting overnight? That's something mine did before I ran the fuel system cleaners through it.
I have ran some Techron through it, but not lately. It has never had an issue with delayed starting. Next time I hook up a the scan gauge I will check fuel trims to see if they are in check.
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