What could be causing Fuel Dilution?

Status
Not open for further replies.
C

canadiantim

Joined
Sep 26, 2005
Messages
62
Location
Alberta, Canada
I have a 2005 Pontiac Vibe with the 1.8litre Toyota motor that is also used in the Corolla and Matrix.

I have had 4 consecutive UOA come back showing "oil should be changed due to fuel dilution".

The car has 48,000km (30,000miles) on it. This last UOA is concerning as it was intentionally a short 3000mile change over the summer with nearly 100% highway driving to test the fuel dilution issue with winter driving out of the picture. Average outdoor temp was probably 75degreesF during this test period.

I'm using Mobil 1 5w30. I also have a MG bypass filter but should not be a factor.

UOA: Viscosity (D445)@100ºC: The last 3 results for viscosity have been 8.976, 8.961, 8.786. The lab has indicated Mobil 1 should be approx 10.35 out of the bottle.

I still have 6 months warranty left but not sure if this is a concern or typical for these motors? If not normal what could be causing this that I could have the dealer examine?

Thanks for your thoughts/ideas.
 
The most likely cause is rich running for some reason. Check that first.

There may also be a PCV issue.

What kind of fuel do you use?
 
I use 87 octane from either Esso or Shell. No cut-rate fuels.

Fuel economy is amazing but I honestly haven't checked the numbers for awhile so need to do this. Your PCV suggestion makes sense. Maybe I'll replace the PCV for this next OCI.
 
Check your air filter as well. We've seen evidence here that certain vehicles, especially newer Hondas, can develop fuel dilution issues/rich mixtures from a clogged air filter. Seems counter intuitive, but Terry Dyson, one of the leading experts on UOA testing, has shown this to be a problem with some vehicles.
 
How much % is the fuel dilution reported ?

If you have an obd-2 reader check the long term fuel trim and see where its at. If you see anything odd (more than 5-7% positive) check how the O2 sensors are doing.
 
Just a quick caveat: Blackstone's reported fuel dilution numbers are not really reliable. The viscosity is a much better indication, especially since Mobil 1 5w-30 should NOT shear.
 
Thanks all.

I need to do my homework and take care of some basics first like the air filter and do a current mileage check. The car is so good on fuel that I probably wouldn't even notice a 15-20% mileage decrease over time at the pump. The OBII check is a good idea.

My viscosity numbers are in my original post.
 
Use a good fuel system cleaner like Amsoil PI. Not too many engine management systems can poll individual injectors so the O2 reads the average oxygen content. You can have rich and lean running cylinders.

That and all the other input should straighten you out.


btw-Blackstone's fuel numbers are found from a table based on the flash point. They do not measure the actual fuel content. Visc may not be a reliable way to factor it either and shear is possible with any oil, synthetic or otherwise, that has any VII. The amount will vary.
 
Been a few months so now for an update:

1) Ran Amsoil PL
2) Had dealer do their "fuel system cleaning". Consisted of running the fuel rail off the commercial bottle of cleaner and a throttle body cleaning. Dealer had no clue how to respond to a few years worth of oil analysis results showing fuel dilution.
3) Had the dealer check TSB's (none), no PCM updates were available, no codes, had them check the operation of the temperature sensors.
4) I replaced spark plugs, PCV Valve, air filter, thermostat, cleaned MAF, cleaned intake temp sensor.
5) Disconnected the battery to reset PCM and then drove the car for a few days to allow the PCM to adapt to the changes and then changed the oil/filter. Mobil 1 5w30.

UOA: Viscosity (D445)@100ºC: The problematic results for viscosity have been 8.976 (9000km), 8.961 (8000km), 8.786 (5000km), 8.720 (1500km), 9.60 (1500km).

A km = approx 0.62 miles.
I gave the lab a sample of my most recent virgin Mobil 1 and the tests showed Mobil 1 was approx 11.40 out of the bottle. This last test was short but my warranty is expiring in a couple weeks.

So, I have noticed a slight reduction in fuel dilution after doing the above "tune-up". I am wondering about getting an emissions test done to show the dealer that "something is wrong". I'm thinking it may just be simpler to drop my injectors off at a local company I've used where they clean and flowtest. I can't see anything else being wrong at this point other than just a characteristic of the computer's injector programming or a leaky injector. I've had the car since new and the UOA showed no fuel dilution in the first couple years. I'm getting about 44MPG, down from 49MPG but it's winter and I have harsh winter tires on.

Should I be concerned with the viscosity dropping from 11.4 out of the bottle to 9.60 in only 1500km (1000miles)????
There was another note on my most recent oil analysis " ALERT! Flash Point
This is bugging me but maybe I'm looking too closely!

Thanks!
 
Been trying to solve a fuel dilution issue that has been showing up in my UOA but not sure if I'm looking too closely. Previous posts in this thread show what I've done to correct.

Should I be concerned with the viscosity of M1 5W30 dropping from 11.4 fresh out of the bottle to 9.60 in only 1500km (1000miles)????

There was another note on my most recent UOA: " ALERT! Flash Point
Any thoughts?
 
Seems like you have a fuel dilution problem, the oil thinned quite a bit in a short period of time.

You heard some of this already but here goes again.

Check mpgs, compare to mpgs prior to problem, same season of the year if you have that data.

Check air filter

Try a good FI cleaner like Redlines product.

Have the injectors checked to see if they are leaking down. A high pressure injector cleaning via the rail is a good idea.

Make sure there are no codes, and that all sensors are working properly. Coolant Temp Sensor, along with the Air Charge Temp Sensor could be out of spec causing a rich condition. HTH
 
Thanks Guys. I agree the fuel dilution is still too high but the dealer hasn't a clue how to resolve or test so I'm paranoid to let them tinker. My warranty expires in 2 weeks.

Demarpaint, I have tried all of the items you suggested and did get a slight improvement but still seem to be getting a pretty good fuel dilution. The car only has 30k miles on it and all highway...
 
Mass air flow sensor may also be a problem. I have had more problems from mass air flow senors than the normal oxygen sensor everyone complains about, however I'm not sure what is your problem. I would also somehow talk with the dealer on you having these problems long before warranty expires, and also you will need to document this with the dealer.

Have you done a google search for fuel dilution, also fuel dilution with your car in the search phrase ?
 
Shearing/Fuel dilution is only really a problem if it affects wear metals - you wear metals are very low, so I wouldn't worry that much.

What are your drving habits, and your subsequent sampling technique? That will have an effect on it.
 
Not sure about things there but my dealers here will honor warranty claims after the expiration if the complaint was documented before expiration. You could inquire as to that there. You MAY have a leaky injector, or maybe the engine is simply good at shearing oil mechanically. My EVO sure is. Doesnt matter what wt, 30, 40, or 50, it will shear to a light 30 wt or even an heavy 20.
 
Originally Posted By: canadiantim
Thanks Guys. I agree the fuel dilution is still too high but the dealer hasn't a clue how to resolve or test so I'm paranoid to let them tinker. My warranty expires in 2 weeks.

Demarpaint, I have tried all of the items you suggested and did get a slight improvement but still seem to be getting a pretty good fuel dilution. The car only has 30k miles on it and all highway...


I would think it is either the faulty injector or improper cylinder sealing, have you checked the color of your old plug ?
 
Status
Not open for further replies.

Similar threads

Sandstorm
Oil Fuel Dilution, the Russian perspective
2
Replies
25
Views
2K
Sandstorm
O
Fuel dilution is nothing new
2
Replies
21
Views
971
Chris142
3UR-FE
2022 Camry 2.5 fuel dilution/viscosity selection question
2
Replies
30
Views
992
SammyChevelleTypeS3
P
  • Locked
Can oil dilution cause a gasoline engine to rapidly consume oil?
2
Replies
31
Views
2K
M56959
B
Long OCI
2 3 4
Replies
61
Views
3K
camrydriver111
Back
Top