Many people keep mentioning that fuel dilution is a problem because it decreases viscosity. It takes 4 - 6 % fuel dilution to drop the viscosity one grade on the average. It (viscosity) is not the problem with fuel dilution. Here are some references:
From Donald J. Smolenski and Shirley E. Schwartz; Automotive engine-oil condition monitoring, (Both former General Motors Tribologists/engineers) contribution to CRC Handbook of Lubrication and Tribology:
Excessive unburned fuel in the oil may reduce oil viscosity so that it no longer provides adequate oil-film thickness in critical areas of the engine. However, much of the fuel may be eliminated when the engine oil reaches stabilized operating temperatures for a long enough time period. Higher temperatures require less time.
Furthermore, the heavier ends of the fuel, which remain after lighter ends are boiled off, have less tendency to reduce viscosity of the engine oil. Fuel in the oil contributes significantly to the loss of the oxidative stability of the oil.
Partially oxidized fuel components, arising during short trip service, can also be condensed in the engine oil and can cause and increase in TAN and a decrease in TBN. These are adverse effects by many ways. This effect can sometimes be diminished at higher oil temps.
Directly from Terry:
Here are some additional areas of complexity to the simple fuel dilution of motor oil issues I am working on at present: Add in ethanol or other sources of enriched fuels that provide tremendous solvency with little if any lubricity.
Most critically important is the severe ECU modifications to compensate for CATALYTIC CONVERTER light off and efficiency for emissions limits, then if any of the fine tuned modern engine is not functioning properly you WILL have higher fuels dilution effects.
Dyson Analysis in most gasoline powered engines targets 0.5% fuels to optimize.
Note too that aromatics can source from the motor oil itself, additive packages and lower quality base oils, contamination, and faulty tune or mechanical performance of the engine. Even more problematic: new hydraulic controlled injection, VVT systems linked in with ECU, OBD, cylinder de-activation, and finally hydrid drive systems add even more stress to the most critical component in the modern engine, the lubricant !
You can see there are no easy answers.
Its not just oil analysis, its Dyson Analysis !
aehaas
From Donald J. Smolenski and Shirley E. Schwartz; Automotive engine-oil condition monitoring, (Both former General Motors Tribologists/engineers) contribution to CRC Handbook of Lubrication and Tribology:
Excessive unburned fuel in the oil may reduce oil viscosity so that it no longer provides adequate oil-film thickness in critical areas of the engine. However, much of the fuel may be eliminated when the engine oil reaches stabilized operating temperatures for a long enough time period. Higher temperatures require less time.
Furthermore, the heavier ends of the fuel, which remain after lighter ends are boiled off, have less tendency to reduce viscosity of the engine oil. Fuel in the oil contributes significantly to the loss of the oxidative stability of the oil.
Partially oxidized fuel components, arising during short trip service, can also be condensed in the engine oil and can cause and increase in TAN and a decrease in TBN. These are adverse effects by many ways. This effect can sometimes be diminished at higher oil temps.
Directly from Terry:
Here are some additional areas of complexity to the simple fuel dilution of motor oil issues I am working on at present: Add in ethanol or other sources of enriched fuels that provide tremendous solvency with little if any lubricity.
Most critically important is the severe ECU modifications to compensate for CATALYTIC CONVERTER light off and efficiency for emissions limits, then if any of the fine tuned modern engine is not functioning properly you WILL have higher fuels dilution effects.
Dyson Analysis in most gasoline powered engines targets 0.5% fuels to optimize.
Note too that aromatics can source from the motor oil itself, additive packages and lower quality base oils, contamination, and faulty tune or mechanical performance of the engine. Even more problematic: new hydraulic controlled injection, VVT systems linked in with ECU, OBD, cylinder de-activation, and finally hydrid drive systems add even more stress to the most critical component in the modern engine, the lubricant !
You can see there are no easy answers.
Its not just oil analysis, its Dyson Analysis !
aehaas
