Fuel dilution -- a real issue?

[pitzel]

Common wisdom in here has been to automatically state that frequent short trip operation leads to a lot of fuel dilution.

While absolutely true in non-fuel-injected vehicles with chokes, there are surprisingly few used oil analysis that actually show this phenomena in modern fuel-injected vehicles that do not have obvious fuel injector problems or malfunctioning instrumentation.

As BiTOG's raison d'etre is to challenge myths that exist about motor oils, does anyone want to offer an argument for or against why one really needs to be overly concerned with fuel dilution on an otherwise properly maintained vehicle used for short cold-weather trips?

 

[medic]

I have to agree with you. This is no longer a problem with todays engines (exceptions: motorcycles, lawnmowers, etc...). Here are a few used oil analysis that I have posted from vehicles that see multiple short trips or extended idling and cold weather.

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[TooSlick]

It would be more technically correct to say that short trip driving - esp in very cold weather - leads to more fuel "contamination" than driving under steady state conditions. With modern fuel injection systems, the "as-tested' equilibrium level of raw fuel in the crankcase will always appear to be low. However what is actually happening is that this fuel is constantly reacting with the engine oil to form insoluble polymeric materials, ie higher molecular weight species. This causes significant increases in viscosity and more rapidly depletes the oil additives.

Partially burned fuel particles actually act as a catalyst for the processes of oil oxidation and nitration, as do water, and certain wear metals like copper compounds.

I hope this clarifies the matter?

Ted

 

[bighead]

Clears it up for me

. Thanks TS.

 

[Nosmo King]

While I agree that FI has cleaned up the fuel dilution problem, there are still a few 'gotchas' out there.

My MB C230 is often driven out of the garage , example for washing etc, on a weekend. Then it is driven back in , and then maybe out later that day.
There have been a few times when the car has been hard to start and one case when it was only firing on 3 cylinders. All due to raw fuel build up in the combustion chamber.

I still believe that short journeys in the winter and combined with stop/start type driving could pose dilution problems.

 

[JeepZJ4.0]

So say, if I take 1 short trip once a week for 2 months but then drive on a 300 mile roadtrip, would that reduce the amount of fuel in the oil or will it be there once its there?

I drive my Jeep to Wal-mart once a week to buy food but I manage to get the Jeep upto operating temp. I go home every 2 months or so. While I'm here, I rarely drive it.

 

[99]

That bit about fuel injection playing a big part in reducing fuel dilution is all fine and dandy....unless you have clogged or leaky injectors. 4.0s for example are notorious for having bad injectors.