Reading Oil Analysis Reports
In Professional BoatBuilder No. 143 our technical editor, Steve D’Antonio, published “Lessons from the Oil Sump,” a comprehensive story about the usefulness of a regular oil analysis program in maintaining engine, transmission, and hydraulic systems. D’Antonio’s text detailed the range of mechanical ailments a laboratory analysis can reveal, from undue engine wear, to contamination with dirt or fluids and the formation of harmful varnish and sludge. He explained how to implement such a program for boats in your care.
Space limitations in the print edition prevented us from reproducing examples of full oil analysis lab reports. D’Antonio has provided some from one of his favorite labs, and those reports are published here. In addition, this online appendix to the story includes links to the laboratory’s website, with further directions on how to read the report and how to take samples. The quality and volume of information contained in these actual reports are a reminder that at $25 to $30 per test sample, this is some of the most affordable diagnostic information you can provide to service yard customers.
The content and quality of oil analysis reports vary dramatically from lab to lab. Ideally, the report should include a host of raw data, including wear metals, contaminant metals, multi-source metals, and additive metals, along with information on fuel, soot, and water contamination, viscosity, and total-acid and total-base numbers, among others. The report should also include a clear, easily understood synopsis that takes into account all the criteria and symptoms evident in the data. While the synopsis is valuable, it’s important that those who review the reports thoroughly understand each and every entry and its potential consequences. They must also resist the temptation to simply rely solely on the conclusions provided by the laboratory, as errors are possible. For instance, oil viscosity is measured at either 40°C or 100°C (104°F or 212°F), depending upon its application. Transmission oils are measured at 40°C, while crankcase oils are measured at 100°C. If, however, the incorrect temperature was applied, the results could be misleading. This how-to document from Polaris Labs provides a basic description of each entry, detailing its significance as a component of the overall analysis process.
While many professionals will emphasize the importance of carrying out regular oil analysis to establish trends for contaminants and wear, a single snapshot can also be valuable. In this case, the lab was able to flag a potentially serious problem with the main and connecting rod bearings after just 13 hours of use. The overall aluminum content appears low, and had the oil been in service for 100 or more hours, this level would be unremarkable; with so few hours on the oil, the level is actually comparatively high and worthy of concern.
This report provides a wealth of information about this hydraulic transmission, not all of which is immediately obvious. High levels of wear metals—aluminum, copper, and lead—are flagged, as they should be. However, if you look closely at the report, the volume of missing information calls into question the validity of results. Most importantly, the manufacturer is incorrectly identified as Caterpillar, when in fact the unit is a Twin Disc. The model, filter type and micron rating, fluid viscosity, sump capacity, lube time, unit time, and an indication of whether the fluid was changed at the time of sampling are all missing. Additionally, the viscosity was tested at 100°C rather than 40°C, even though the latter is typically used for transmission fluid analysis. The individual who prepared this sample failed to properly complete the forms and has, therefore, negated the value of the report. Note that the report includes the warning: “Comments are advisory only and are based on the assumption that the sample and data submitted are valid. Missing fluid or component information limits the evaluation.” Once the missing information is provided, this report can be re-issued with a far greater degree of reliability. As it turned out, when that was done, the flagged metal levels, particularly the copper, were deemed normal for the lube time in this transmission, which has copper alloy clutch plates.
For additional information on oil testing results and protocols, visit the following links:
- A sample report from another reputable lab.
- This document explains the importance of providing proper lube time.
- This one explains the importance of providing proper equipment information.
- This guide gives step-by-step directions for filling out sample labels.