Open Question on Fuel Dilution

I would suspect the engine not getting hot for long enough time... especially if you are a high MPG seeker. You could do an easy test of this by taking your sample (at around 5,000 miles), then drive the car at freeway speeds for an 1 hour or more. The idea being to make the engine run continuously and to get the oil nice and hot... as well as give any light ends enough time to boil out. Upon completion of the trip, take a second sample. send them both in and compare them.

If engine temperature is the issue, then you should consider changing your oil more often... It just indicates that your driving style does not give the engine an opportunity to run hot long enough.

 

bad PCV might not necessarily cause a rich mixture, but if the fuel vapor is not actively purged it's going be collected in the oil. so yes, that can contribute to fuel in the oil. ours will be done at 60k and i believe he put that in our "services you need and when" thread.

the question is how does the fuel get into the crankcase? blow-by. severe blow-by is caused by piston ring wear. but any engine, even a new one, is going to have miniscule amounts of blow-by.

other failures contribute to how much fuel gets into the oil- spark plugs that don't ignite the fuel, mass airflow sensors that cause the system to run rich, carbon buildup on valves or piston heads. there are a ton of things that can cause incomplete combustion. and the more fuel that's not combusted, the more chance it's getting into the oil.

now if you honestly think there's a major problem with your engine, a compression test will tell you. this will tell you the condition of your valves and piston rings. you can even determine which of the two is at fault if there's a problem.

all engines wear as time and mileage goes by- so you need to account for the fact that your rings will wear and allow more blow-by as time passes. this is just a fact of life. seals and gaskets and etc are technically maintenance items. they wear. DH's camry engine (i say engine and not car because the body's dead) came with a 7.5k mi oil change interval but since it has 140k on it, it's been every 3k since the day we bought it.

 

<div class='quotetop'>QUOTE(dmckinstry @ Jun 9 2007, 12:35 PM) [snapback]458780[/snapback]</div>

Unless you have a lot of miles (say more than 75,000 miles... and really 100K +), and given your comments about zero oil consumption, I would focus on the engine just not getting hot enough AND not long enough.

Your comments about going 5 miles at 55 and 3 to 4 miles uphill... tell me as much. I was talking about 60 to 100 miles under load (say doing 65 to 80 MPH)... continuously. That's probably the easiest test you can do.... while enjoying the car too...

John

 

<div class='quotetop'>QUOTE(dmckinstry @ Jun 9 2007, 07:58 PM) [snapback]458892[/snapback]</div>

Dave

I did post a reply to the other thread about fuel dilution, and can only repeat that the sodium is almost certainly from the dealer oil. See if you can get a virgin sample off them, wishing you luck with that too.

If you recall, my dealer oil had very high sodium too

I take the sample at my hobby farm after driving 140 km, so in theory any moisture or fuel in there should have disappeared. But any excess moisture or fuel should also cause permanent viscosity loss. I believe you PM'd me awhile back stating your UOA had indicated substantial viscosity loss.

What I will do this week is take a sample of the Mobil 1 0W-30 with around 7,000 km on it, with the motor cold and the Prius not having highway driving in quite a while. I'm now curious if this is a widespread Prius issue.

Though if this was an issue, a lot of Prius cars in the EU with their normal 12 month/10,000 mile interval would have had problems by now.

j

 

Moving your car into your garage right before taking a sample is another way to ensure you get excess fuel in your oil.

I have heard of some people having better luck with aftermarket air filters, in order to reduce fuel dilution. This is especially true for Honda engines. Fram makes good air filters.

 

Before driving off to work this morning, I pulled a sample. The Prius has been sitting for over a week, and had been used for short city drives before that. Actually most of the Prius driving since I got my FJ Cruiser in March has been city only. I now use the FJ to drive out to the hobby farm.

So if there is fuel dilution, I should have it by now.