Originally Posted by Rage

Attached are my engine oil analysis since the motor was new, one per season. Unfortunately my engine is a moving target since I have made modifications each winter which are noted at the bottom of the oil analysis history sheet. After each modification there was a recalibration phase of the Mercruiser PCM555 ECU during which time was spent running boat with ECU calibration at certain rpm's being richer than optimum always occuring at low rpm's and mid range rpm's. A/F target is 12.5. The stock 496HO produced moderate to heavy transum sooting. The next two seasons was about half that. This last season the tune was more in the low 13's A/F with lowest in the low 12's and transum soot was almost non existant. This fact makes the latest high gasolene content in the oil extermely confusing to me. Prior to installing the Amsoil oil for this most recent season I broke in the engine rebuild for a total of three hours with two oil and filter changes, one after 15 min engine flush and the other after 3 hours run time with stock Merc 20W40 oil. The high gasolene content during the preceeding season was expected since early ECU cal was in the 10's and flooded the engine followed later by an intake lifter failure that ran the engine on seven cylinders flooding that cylinder with raw gas for a time. As noted I have run stock Merc, Mobil 1 V Twin and Amsoil Racing oils. Analysis of the virgin Amsoil and Mobil 1 are also included. I tend to spend a lot of boat hours cruising at 2500 - 3000 rpm's and wake boarding at similar speeds.

You knowledgable comment on the results is solicited especially relative to any red flags I should be aware of.

Originally Posted by minxguy

I is unfortunate that you are having fuel dilution issues, you can see the impact it has on the viscosity.
Are both the used Amsoil results from the same blend as the virgin sample?

I see in the virgin samples that Mobil V-Twin is a much heavier 50 than Amsoil. The Mobil is almost 14 SUS heavier than the Amsoil right out of the bottle.
The SAE range for 50 weight at 210 is 85-110 SUS. The Mobil is very strong at 102.7, the Amsoil is barely a 50 with 88.8.

If you are going to "running fat" the heavier 50 (Mobil) will stand up to fuel dilution way better because it starts out heavier(thicker). All the oils run lost viscosity, the 50's dropped to a 40 and the Mercury dropped to a 30. 40 wt at 210 is 70-85 SUS, the Mercury ended up at 62.7.

If you feel that you ECM is as close as you are going to get it and the fuel ratio is good, I would start looking at oil temp to see if you can cook some of the fuel dilution away. Oil has to be at a min 180-190, on the high end 240 is ok.

Ken

Originally Posted by Rage

Ken,

Thanks for the input.

No the virgin Amsoil was from the first batch I purchased. The second Amsoil change was a batch purchased later.

All data was with the stock 496HO oil cooler which is not thermostatically controlled so the engine oil temperature is not controlled. However that oil cooler is insufficient capacity for the hp I am now running. I have been experiencing significant oil pressure drop at WOT with the latest engine configuration even with the addition of a high volume oil pump with that build. I have been advised that is likely do to high oil temperatures because of the insufficient oil cooler capacity. I noted that fact to the oil analysis lab and is why their comment stating that oil overheat was not evident in the oil. I had made quite a few A/F vs RPM runs up to WOT for the ECU recal work which caused the noted oil pressure drop. Should that have cooked out the gas?

I am adding a thermostatically (212F) controlled oil cooler of appropriate capacity this winter as well as an oil temperature gage.

I now recall that the fuel pressure when the engine is turned off now is bleeding off in a few hours where as before it would hold almost indefinately. That I suspicion may be my problem ie a leaking injector dumping some fuel into the engine everytime I shut down. Is that enough fuel for the gas content in the oil recorded this last time do you think?

What about the double the iron content in the used Mobil1 versus the Merc and both the Amsoil oils when normalized (linear) for the same engine hours?
THanks again.

Bill

Originally Posted by minxguy

Bill, you could be chasing two problems for your loss of pressure at WOT, your oil cooler could be way too small causing your oil to see 300 plus degrees compounded with you have a fuel dilution problem. At 300 degrees of oil temp, you would flash off any fuel in the oil, but per your post you spend a lot of time in the 2500-3000 range. I would imagine you would be able to smell the fuel in the oil at an oil change.
It doesn't take much fuel (a very low viscosity liquid) to impact the viscosity of oil. (Mobil V-Twin would hold up better, heavier t start). Any %age of fuel in the whole number range (X. VS .X) is not good.

Let me do some research/thinking on the iron side of your question.

Bill, the test results for the Mobil 1 include a bunch of valve train work, I suspect this is where the iron has come from. As the other two tests show, the PPM of iron has dropped.

Still pound for pound and dollar for dollar, I would continue to purchase the Mobil V-Twin.

My 2 cents on the whole thing and I hoped it helped.



Ken

Originally Posted by Rage

Ken,

You have been helpful.

To clarify I do/did spend a lot of time at 2500 - 3000 rpm but just before I changed the oil this last time I did none of that but did do a whole bunch of WOT running (including with the oil pressure drop) to obtain A/F vs RPM data for the ECU recal work. That same day after the last of these runs I changed the oil and sampled for the oil analysis (after I warmed to oil for about 15 min. at idle. So I guess by inference I could not have been in the 300F oil temp range as explanation for the oil pressure drop because I still had fuel in the oil afterwards. Does that make sense?

It is plausable that the new heads/valve train produced the high iron content. I did do the solvent wash and soap and power wash to the bare iron heads before install. Maybe iron oxide was the culprit. The heads also came with the thin bronze guides which were snug on the valve stems. I contribute the high copper content to the guide break in wear as well. There of course would then be no iron wear from the valve guides. I retained the original lifters but changed to Crane aluminun roller rockers and Crane cam. I will give the M1 another shot sometime later after I use the Amsoil I have.

Do you have any data on at what A/F threshold gas starts showing up in the oil for NA engines in quantities that are significant to the oils performance ?

At lets say 3% gas can you smell it from the oil fill tube?

Thanks,

Bill

Originally Posted by 07DominatorSS

12 PPM of Silicon??? That is new oil. Silicon is typically dirt. Brand new dirty oil, hmmm.

Originally Posted by Hydrocruiser

Fuel Dilution-
If unburnt fuel is allowed to enter the lubrication system, the oil will become thinner and more volatile. Both will result in higher oil consumption. Excess fuel can enter and mix with the oil via a leaking fuel injector, fuel pump problem, and restricted air intake or through excessive idling.


A call to Merc is in order if under warranty. 3% per oil change is not acceptable.

Originally Posted by Rage

What is it about excessive idleing that puts fuel into the oil?

Originally Posted by Hydrocruiser

The most common cause of oil becoming diluted with gasoline is idling - when the engine is cold there are greater clearances between the piston rings and the cylinder walls, and this greater clearance allows small amounts of unburned fuel to slip down into the crankcase.

After a long idle run full bore to burn it off.

If you have 3% gas in the oil; V-Twin M-1 is good cheap insurance.