The truth about fuel dilution

[mousejunks]

I was just going through my warranty guide and noticed there was a section about oil consumption. We all know it is normal for some oil to be burnt between oil changes. However what interested me was a paragraph which stated that start-stop traffic causes fuel dilution (i.e. contamination of fuel in engine oil). The only way to avoid fuel dilution is to travel at a constant low speed which is impossible 90% of the time.

[CROSSBOLT]

Reads like they "covered their butts." Have yet to see any significant dilution or consumption or leaks in ANY of the Kymco models we have or had.

[Kansas kymco]

I have never known it to be a issue with gas engines it's called wash down in the Diesel world from idling the motor for long periods of time. 

[Iahawk]

it's becoming more of an issue in the car world with the adoption of the DI (direct injection) turbo motors. Some manufacturers seem to have more problems than others.

For people that do used oil analysis there is a category for fuel dilution..certain motors with extended oil change intervals combined with short tripping can be more or very prone to it.

In the scooter world?  Not an issue that I'm aware of..

[de dee]

  I use to hear about that back in the 1940 s., when motors had low compresion now my piaggio B V 350 has 12 to 1 and that was high speed racing just a few years ago,. engines are a lot tighter today , I wonder how high it will be in another 50 years  or will it be electric motors with batterys that will last hundreds of miles, they will get better compression on the Wankel we may have a wankel in our scooters WOW 30,000 RPM motors

[Kansas kymco]

it's becoming more of an issue in the car world with the adoption of the DI (direct injection) turbo motors. Some manufacturers seem to have more problems than others.

For people that do used oil analysis there is a category for fuel dilution..certain motors with extended oil change intervals combined with short tripping can be more or very prone to it.

In the scooter world?  Not an issue that I'm aware of..

I'm aware of carbon build-up on the intake valves with DI. I know some manufacturers have added another injector on the intake to help alleviate carbon buildup.  Is this adding to fuel wash down in DI motors?  Did not know it was a issue.

[stuo]

What a crock!

[Wil B.]

Fuel dilution is a real thing. My 2018 Mitsubishi is awaiting a new engine (warranty replacement) because of this.  The engine began making a ticking noise and dealer diagnosis was "cylinder scoring due to overfueling of the engine."  The fueling system poured too much gas into the cylinders, which diluted the oil, and caused the scoring of the cylinders. No warning lights and the engine still ran fine.

Having said this, I doubt this would ever be a problem on our small engined scooters. They are designed for stop and go - short distance travel and it looks like Kymco is just playing CYA on this one. Unless they know something we don't.

[Kansas kymco]

Fuel dilution is a real thing. My 2018 Mitsubishi is awaiting a new engine (warranty replacement) because of this.  The engine began making a ticking noise and dealer diagnosis was "cylinder scoring due to overfueling of the engine."  The fueling system poured too much gas into the cylinders, which diluted the oil, and caused the scoring of the cylinders. No warning lights and the engine still ran fine.

Having said this, I doubt this would ever be a problem on our small engined scooters. They are designed for stop and go - short distance travel and it looks like Kymco is just playing CYA on this one. Unless they know something we don't.

I'm curious how over fueling occured? When the computer detected the rich mixture it should have  cut back on fuel or thrown a code. The computer should keep the optimum fuel mixture on a injected motor.  I take it was a failed injector?

[JJJoseph]

What model and engine is this?  Can't even get close without knowing what it is.

[mousejunks]

What model and engine is this?  Can't even get close without knowing what it is.

Kymco Downtown 350i

[Wil B.]

I'm curious how over fueling occured? When the computer detected the rich mixture it should have  cut back on fuel or thrown a code. The computer should keep the optimum fuel mixture on a injected motor.  I take it was a failed injector?

The dealer has not gone into details,  but there were no warning lights or check engine warnings the entire time.  I found a TSB from 2014-15 Mitsubishi Mirages dealing with the same problem saying they would re-flash the computer and if that didn't  work....replace the engine. So all I really know is that's a fueling issue, and the end result is a destoyed engine.

[CROSSBOLT]

Local guy had Kawasaki side-by-side Mule or something and that thing had a TERRIBLE problem with fuel dilution of lube oil. In the shop 20+ miles away about 4 times. Owner finally dumped it back on the dealer and took home a Polaris.

[Kansas kymco]

Local guy had Kawasaki side-by-side Mule or something and that thing had a TERRIBLE problem with fuel dilution of lube oil. In the shop 20+ miles away about 4 times. Owner finally dumped it back on the dealer and took home a Polaris.

Was it the gas or Diesel mule? I owned a Diesel mule without issues, other the slow as molasses.

[CROSSBOLT]

Was it the gas or Diesel mule? I owned a Diesel mule without issues, other the slow as molasses.

Gas. They even changed the engine and the new one had the same problem!