QuestionQUESTION: This is a generic question related to turbo charged engines and the level of acceptable fuel in the engine oil following prescribed OEM oil changes.
All engines have fuel forced into their engine oil through the rings via blow back. The question is, how much is acceptable (% fuel in oil)?
ANSWER: Diluted engine oil may cause your engine to suffer from excessive heat, wear and noise, and will often lead to failure if the issue is not resolved. Even after adding new oil the simple operation of that engine begins to impact the functionality of the oil. An example of this is the degradation of lubricating oil by the presence of fuel contaminants.
The tests to determine fuel to oil dilution are not something you can do at home. Flash Point testing and Gas Chromatogtaphy (GC) are the two methods most commonly used. What actual numbers to look for I can't tell you only an oil testing facility can and from what I know they would require several test samples to establish a basis.
The simplest way is to field judge the color and liquidity of the oil when cold. Gasoline odor will be present in heavily diluted oil and darkening will result from hydrocarbon wash - so if it looks old and smells old then it's time for a change.
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QUESTION: I have read figures from 2-5%fuel in engine oil are the limits but clearly this figure should be known by the manufacturer of the engine. I would hate to have to rely on my nose to tell when it is time to change the oil. So are we to rely upon an oil testing company to tell us the acceptable level of fuel dilution? How would they know what acceptable levels are for various engines?
AnswerMazda has no data on oil to fuel dilution rates and percentages. The only company I know of that has run these test an have results published is Caterpillar Inc., these are on large scale Diesel engines.
I'm afraid I have no further technical data to share on this, the one thing for sure is you'll have no means to test it yourself an oil testing facility will and the GC test is the most accurate. No idea of cost per test.
Beyond that;
I would suspect a viscometer reading the oil in it's original unused state and then again at varied use points could tell how the oil is being affected. Obviously a great drop in viscosity inside of 3,000 miles would be a cause for alarm. A blind comparison with another vehicle may help determine if your car is off the chart or not.
Best of luck.
