Fuel in engine oil

[Peter Werner]

Fuel is accumulating in oil. Brand new DF300, installed early Oct, 2012, less than 17 engine hours to date. Has been operated per Suzuki guidelines. Have drawn down ~ 1 qrt @ ~ 7hours, now @ 17 hours - oil level high again. Question: What are the most likely causes?

[noelm007]

running too cold, not running at high enough RPM or doing very short runs are the usual reasons.

[Peter Werner]

running too cold, not running at high enough RPM or doing very short runs are the usual reasons.

Thanks. Engine has been run for reasonable durations and at cruising RPMs of ~5000. Also has been run @ ~ 6000 RPM for reasonable durations for prop tests. No long term low RPM operation. Engine performs great. Hot engine temp is ~145 degrees. ~ 2 quarts of fuel into crank case seems like a lot within 17 hours operation. Oil was very black @ ~ 8 hrs - still is of course. What's likely hood of cylinder/ring/piston problems? Engine is going in for early 20hr check up. What should I insist on?

[Peter Werner]

Thanks. Engine has been run for reasonable durations and at cruising RPMs of ~5000. Also has been run @ ~ 6000 RPM for reasonable durations for prop tests. No long term low RPM operation. Engine performs great. Hot engine temp is ~145 degrees. ~ 2 quarts of fuel into crank case seems like a lot within 17 hours operation. Oil was very black @ ~ 8 hrs - still is of course. What's likely hood of cylinder/ring/piston problems? Engine is going in for early 20hr check up. What should I insist on?

Additional ?s: What internal engine phenomenon, other than mechanical problems (pistons, rings or cylinders) would result in fuel passing to crankcase? ie: what is there about low engine-speed or low operating temp that would result in fuel > crankcase? ie: Reduced piston expansion?

[redlowrey]

Fuel leaking into the crankcase has got nothing to do with pistons or rings, it is probably leaking internally from the diaphram of the low pressure fuel pump. The engine would have to be running like a dog and blowing heaps of black smoke to to start increasing the level on the dip stick.

[Talklessridemore]

Unburn fuel is passing thru piston rings.. That's why you have fuel in the oil
It can happen when engine temp is too cold - one (or more) of fuel injector
Are not firing - prop maybe too big ?- too much leak down ?
- bad compression ? Week spark ?
Have ur dealer take a look at it.
It can happen to any motors

[Peter Werner]

Engine in for 20hr check. All engine data looks good except for low engine temp. While running at cruising speeds (~5000RPM) engine temp is ~140F Suzuki apparently has two thermostat options - 60C/140F & 70C/157F. Suzuki had the shop return it to me without thermostat change??? Unofficial Suzuki feedback is that the 60C option is due to warm surface water temps in Florida??? Unless engine water in-take temps are near engine operating temps what difference does it make? Both options seem low to me. Thanks again - Pete

[Moonlighter]

Sounds too low to me.

My DF115 runs consistently around 70 deg C which is 158F.

At 140 your is too low IMO. Here inAustralia our typical water temp in summer is about 75F which s quite pleasant to swim in, not sure how that compares with Florida. I think you have th wrong thermostat.

[Peter Werner]

Thanks for reply - all helps. Actually I'm NOT in Florida - I'm in far NW Washington - cold surface water! The "Florida" "excuse" was "feedback" from Suzuki. Next week I will "push" dealer to find out what Suzuki is going to do. Right now I'm back in "Live-Aboard-Slip" in Blaine, WA - with engine that I will not put many hours on until early '13. It sucks!! after spending gobs of $s to re-engine from an IO. Now - LOTS! of fuel in crankcase.

[Talklessridemore]

I'm here in so cal.
Mine is 2011 zuki df 250 With 21,5 pitch ,When it was at idle engine temp Was 145 (summer season) when it was at 5,700 rpm , engine temp was 156

But i use 91 octain fuel. Seems like it burns quiter and cleaner. I know i don't have to use 91 ..but i like it
Some people say. I waste of money.. But i used to pay 8 dollors a gallon when i was out of country.. Paying extra 40 cents is not. A big deal for me..
Try different thermostats first..

[nelbur]

I believe it is fairly common for new four strokes to make oil until you get the rings sealing good. I would install the hotter thermostat so the oil warms up more. That should evaporate the fuel out of the oil better. My four stroke Suzuki has about 250 hours on it and has finally stopped making oil.

[redlowrey]

Mate if the oil level on the dip stick is increasing and it smells like petrol you have a problem, check the low pressure fuel pump.

[Peter Werner]

Thanks all for feedback. Sent message to Suzuki customer service. They are now going to replace thermostat and all injectors. Will likely have to wait until spring to confirm - as it's not likely we will get many hours on it till then. Will provide results when we know. Thanks again - Pete

[Trophy98]

DF300 Making Oil

Sounds strange - my 2007 DF300 was launched in 2008, and I have put 200 hours on it each year, currently at 900 hours. Thermostats were upgraded to the higher temperature in 2010, as recommended by Suzuki. I have never made oil (gas added to oil) to any noticeable degree. Oil is changed every 100 hours (twice a year). I have heard of 4 strokes "making oil", which is not unusual, but yours does seem excessive.

[Peter Werner]

Thanks for reply. Thermostats and injectors have been replaced mid-November. No appreciable hours since - so have no results yet. No serious hours intended until spring. Will update thread after more hours.