Fuel contamination can be an important indicator of both lubricant condition and developing mechanical problems in bus engines. When unburned fuel enters the crankcase and mixes with the engine oil, it changes the lubricant’s physical properties and can compromise its ability to protect critical components.
This contamination lowers both oil viscosity and flash point. As viscosity falls, lubricant film strength and load-carrying capability can decline, increasing the potential for friction-related wear. Persistent or severe dilution can ultimately contribute to lubricant degradation, deposits, and damage to oil-wetted components.
Potential sources of fuel dilution include defective or leaking injectors, over fueling, and leaking fuel/oil heat exchangers. Operating conditions can also influence dilution, making laboratory results particularly useful when they are evaluated as part of a broader engine-condition monitoring program.
A well-designed testing program can evaluate:
- The percentage of fuel present in the engine oil
- Changes in lubricant viscosity
- Flash-point reduction
- Wear-metal concentrations
- Oxidation and other indicators of lubricant degradation
The significance of fuel dilution extends beyond determining whether the oil should be changed. A rising concentration can provide evidence that maintenance teams should investigate the engine itself. Otherwise, simply replacing contaminated oil without addressing the source may allow the condition to recur.
Eurofins TestOil’s dedicated fuel dilution testing uses gas chromatography to quantify fuel in used engine oil. For transit fleets, trending is particularly important. A single measurement provides a snapshot; repeated sampling establishes a baseline and makes changes easier to recognize. Eurofins TestOil’s used oil analysis for transit fleets emphasizes evaluating results in the context of previous samples, mileage, component age, lubricant additions and maintenance history.
That broader perspective enables reliability teams to use fuel dilution not merely as an oil-quality measurement, but as an actionable indicator of engine health.
To schedule Used Oil Testing visit https://testoil.com/trustplus-oil-analysis/start-testing-now/; call 216-251-2510; or email testoil-sales@et.eurofinsus.com.
With more than 30 years of experience in the oil analysis industry, Eurofins TestOil focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil and fuel analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, Eurofins TestOil provides customers with same-day turnaround on routine oil analysis testing.
About Eurofins – the global leader in bio-analysis
Eurofins is Testing for Life. Eurofins is the global leader in food, environment, pharmaceutical and cosmetic product testing, and in discovery pharmacology, forensics, advanced material sciences and agroscience Contract Research services. Eurofins is also a market leader in certain testing and laboratory services for genomics, and in the support of clinical studies, as well as in BioPharma Contract Development and Manufacturing. The Group also has a rapidly developing presence in highly specialised and molecular clinical diagnostic testing and in-vitro diagnostic products.
With over 61,000 staff across a network of 940 laboratories in 59 countries, Eurofins’ companies offer a portfolio of over 200,000 analytical methods. Eurofins Shares are listed on Euronext Paris Stock Exchange.
