Fuel in the oil

[Scout]

I sent a sample of my used oil to Blackstone Labs for an analysis and everything came back fine except I had 1.5% fuel in the oil. This caused the viscosity to drop my 40 wt oil down to a 30 wt range. Any idea what's causing this?

My bike is an '07 and I've been using it mostly for back and forth to work which is 27 miles each way on the freeway. Some stop and go freeway traffic in the afternoons (hey... this is Seattle!). So the bike always gets the oil up to temperature on each ride. I also do some weekend cruising, so again, no short trips or extensive idling.

The oil I used was Shell Rotella-T-Synthetic 5w40 and I use a Mobil 1 oil filter. The oil had 2200 miles on it when I pulled the sample and the bike has 7350 total miles on it. Everything is stock. I had the ECU replaced on the recall during this oil run and noticed a 1 or 2 miles per gallon drop in my average fuel economy.

The 1.5% fuel isn't a dramatic problem, but is sort of a "watch" item per the lab's averages. Does the FJR tend to dilute the oil or does mine have a problem?

 

[FJRay]

I don't recall of this being discussed before. I used to do oil samples all the time when I was in the marine diesel biz but Haven't done it on the bike. The only way to get fuel in the oil would be through the injection system via a faulty injector. Generally a one time test isn't real cause for alarm. If you do a sample on each oil change for awhile and track the results it may give a better indication of a problem. I wouldn't think that 1.5% is a real concern but if it continues to get worse then go after the injectors or if you have done the jumper thing it may be to rich and unburned fuel is getting passed the rings which wouldn't be a good thing for the cylinder walls.

 

[dcarver]

I'm afraid to send my oil in for analysis.

Don't ask, don't tell.

 

[Geezer]

I don't recall of this being discussed before. I used to do oil samples all the time when I was in the marine diesel biz but Haven't done it on the bike. The only way to get fuel in the oil would be through the injection system via a faulty injector. Generally a one time test isn't real cause for alarm. If you do a sample on each oil change for awhile and track the results it may give a better indication of a problem. I wouldn't think that 1.5% is a real concern but if it continues to get worse then go after the injectors or if you have done the jumper thing it may be to rich and unburned fuel is getting passed the rings which wouldn't be a good thing for the cylinder walls.

This is an interesting discussion. When I read this post I was thinking that the fuel had to be getting past the rings in order to get into the oil. I suppose it could also squeeze through a bad gasket or maybe even the valves seals, but I don't understand the bad injector scenario. Can you tell us more?

 

[Fred W]

When you stop your bike there is still pressure in the fuel rail. A leaky injector could allow the raw fuel to drip into the combustion chamber (through an open valve) when the engine isn't running. It would eventually work it's way past the rings and into the crankcase.

This would be a bad scenario as the raw fuel would also wash (some of) the oil off the bore walls meaning you'd be causing a lot of wear during cold starts. You'd think the engine would start poorly and spin over too fast if this were the case due to the loss of ring compression, but if it was happening on only one cylinder you might not notice it.

It was a common problem with early Mazda Rotary engines.

 

[Geezer]

When you stop your bike there is still pressure in the fuel rail. A leaky injector could allow the raw fuel to drip into the combustion chamber (through an open valve) when the engine isn't running. It would eventually work it's way past the rings and into the crankcase.
This would be a bad scenario as the raw fuel would also wash (some of) the oil off the bore walls meaning you'd be causing a lot of wear during cold starts. You'd think the engine would start poorly and spin over too fast if this were the case due to the loss of ring compression, but if it was happening on only one cylinder you might not notice it.

It was a common problem with early Mazda Rotary engines.

Ah, that makes sense. In this scenario the fuel is, in fact, getting past the rings, just not while the engine is running.

 

[mike25]

You might try a running a couple of tanks of 'Sea Foam' through the system.

It just might clean a leaky injector.

 

[Scout]

When you stop your bike there is still pressure in the fuel rail. A leaky injector could allow the raw fuel to drip into the combustion chamber (through an open valve) when the engine isn't running. It would eventually work it's way past the rings and into the crankcase.
This would be a bad scenario as the raw fuel would also wash (some of) the oil off the bore walls meaning you'd be causing a lot of wear during cold starts. You'd think the engine would start poorly and spin over too fast if this were the case due to the loss of ring compression, but if it was happening on only one cylinder you might not notice it.

It was a common problem with early Mazda Rotary engines.

Interesting thought. All this discussion has me a bit worried about my injectors now! Any way to verify if this is happening?

 

[charon76]

When you stop your bike there is still pressure in the fuel rail. A leaky injector could allow the raw fuel to drip into the combustion chamber (through an open valve) when the engine isn't running. It would eventually work it's way past the rings and into the crankcase.
This would be a bad scenario as the raw fuel would also wash (some of) the oil off the bore walls meaning you'd be causing a lot of wear during cold starts. You'd think the engine would start poorly and spin over too fast if this were the case due to the loss of ring compression, but if it was happening on only one cylinder you might not notice it.

It was a common problem with early Mazda Rotary engines.

Interesting thought. All this discussion has me a bit worried about my injectors now! Any way to verify if this is happening?

Ride it. You're changing your oil often enough that even if that is the case it's not going to cause long term damage. Should your sample from your next oil change in another 2200 miles show the same thing the perhaps it warrants further investigation. We regularly send oil out for testing. A one time test isn't enough to get worried about. Should it be an ongoing thing there are a variety of tests that can be done to find out which, if any, injectors are leaking. Where the fuel is getting into the oil from. The easiest thing to do if you are really worried about it is check the spark plugs, see if any of them vary in color from the others. That'll give you an idea as to what injector is causing the issue. Otherwise just ride it till the next test results.

 

[bergs]

I'm inclined to suggest that, in addition to a fuel pressure leak down getting past an injector, a possible sticky injector which might induce the situation you describe.

With the awsome aweful quality of fuel we're getting, it doesn't take much more than a few weeks to get gummy......if your FJR was sitting for any amount of time then the possibility exists that you could have at least one sticking injector, albeit minor.........possibly.

Add another vote for the SeaFoam treatment and maybe do another oil quality test in 6000 miles (2 oil changes) just to see.

My .02

 

[Fred W]

Seafoam or Techron. If the injectors are gummed up and leaking either of these should help.

I don't think that your problem is as severe as how I spelled it out. If it was you'd likely have strange starting behavior due to the flooded cylinder.

 

[Scout]

Seafoam or Techron. If the injectors are gummed up and leaking either of these should help.
I don't think that your problem is as severe as how I spelled it out. If it was you'd likely have strange starting behavior due to the flooded cylinder.

OK, makes sense. Thanks for the advice! I've got some Chevron Pro-Gard Fuel Injector Cleaner with Techron so I'll put that in and see how it goes... Would be nice if it restored my gas mileage as well!

 

[Jimstan]

Hi Scout:

Back in the day we would blip the throttle before shutting down to clean the plugs and cylinder of carbon,

The theory was that the unburnt gas would clean the carbon. If you did it to much your oil would smell of gas that had leaked through the rings.

Not sure if F.I bikes do the same thing, if so just let It go back to idle before shut down.

Just my thoughtsJimstan

 

[GPRIDER]

I sent a sample of my used oil to Blackstone Labs for an analysis and everything came back fine except I had 1.5% fuel in the oil. This caused the viscosity to drop my 40 wt oil down to a 30 wt range. Any idea what's causing this?
My bike is an '07 and I've been using it mostly for back and forth to work which is 27 miles each way on the freeway. Some stop and go freeway traffic in the afternoons (hey... this is Seattle!). So the bike always gets the oil up to temperature on each ride. I also do some weekend cruising, so again, no short trips or extensive idling.

The oil I used was Shell Rotella-T-Synthetic 5w40 and I use a Mobil 1 oil filter. The oil had 2200 miles on it when I pulled the sample and the bike has 7350 total miles on it. Everything is stock. I had the ECU replaced on the recall during this oil run and noticed a 1 or 2 miles per gallon drop in my average fuel economy.

The 1.5% fuel isn't a dramatic problem, but is sort of a "watch" item per the lab's averages. Does the FJR tend to dilute the oil or does mine have a problem?

This was discussed several years ago. I think the concensus was that it was the nature of the beast and It is not going to damage anything.

GP

 

[Scythian]

I'm afraid to send my oil in for analysis. Don't ask, don't tell.

Only if you suspect jism in the oil....

 

[Baz]

Scout:

Your oil sample represents only a small picture of what is going on. It's common to find gas in your crankcase on newer engines, and worn out engines. I might suggest that you have another sample done later on. 7350 is not a lot of miles. (Gas can wash past the piston rings which have not yet seated, or in an old bike, piston rings which are worn.

I would suggest that your injectors are not gummed up after 7350 miles, and your injectors spray into the throttle bodies. Gummed injectors would cause poor running, and not leakage that would fill your crankcase up with gas. (You would have a rough running bike in this case).

I don't know if you have put a PC-III on your bike, and maybe a new map, but if your bike is running rich, it can cause gasoline to was off the cylinder walls into the crankcase. If you have not touched the stock maping on your FJR, your CO2 sensor would pick up a rich condition, and you would be getting error messages on your computer.

I would have another sample done on your next change if you are that concerned, but I bet this condition will improve.

 

[radman]

If an injector is leaking down, you'd see it in the fact that hot starts would be problematic, both in cranking time and rough running once started. Cold starts would also be problematic, as there would be insufficient rail pressure to ensure a quick start. The FJR runs rich as a ***** on a cold start-numerous cold start problems in the past can and have been traced to a cold shutdown, leading to wet plugs and/or flooded chambers. Short tripping will lead to heavy loads of fuel in the oil, contributing to this is the fact the FJR has an oil cooler-unless run hard, the oil doesn't get blazing hot on this bike, and this slows the evaporation of unburnt fuel from the oil. State of tune can affect the amount of fuel in the oil-a misfire can dump lots of raw gas, left for too long, can cause rapid ring wear which will set the condition for the remaining life of the motor. Also, +1 on Baz's post.