Engine Oil / Crankcase Treatment: The Test Results
A head-to-head test of 1 engine oil / crankcase treatment options with the measured results for each. See how they ranked and watch the full test video.
Diesel fuel
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The measured results
Every number below is read straight from the test. Scroll sideways to see all measurements. Products are listed in the order they finished.
| Product | Lubricity Test Pure Diesel | Lubricity Test Diesel Oil Mix | Safety Data Sheet Figures | Engine Rpm Test | Post Run Filter Inspection | Sludge Cleaning Comparison | Overheating Observation | Compression Test |
|---|---|---|---|---|---|---|---|---|
| 1Diesel fuel | 100% diesel on the lubricity tester's bearing showed a lot more scoring/damage than 10W-30 oil, described as clearly not a very good lubricant compared to conventional 10W-30 | a one-part-diesel-to-four-parts-oil mix showed only a little bit more bearing damage than 10W-30 alone, described as not a whole lot of difference and not likely to cause catastrophic engine failure | flash point 126 to 152 F (51.6 to 66.6 C), boiling point 320 to 700 F, autoignition temperature 490 to 545 F; narrator notes the autoignition temperature is high enough that fire risk from running the engine is unlikely, but the relatively low 320 F boiling point means a lot of the diesel may flash off/evaporate while the engine runs | baseline with 10W-30 oil (from a previous video, same fixed-throttle/no-governor small engine setup) was just under 3,400 RPM; no specific RPM figure is given anywhere in this transcript for the engine running on straight diesel, a genuine gap rather than a caption error | diesel drained from the crankcase after the run showed a metallic color, and filtering it through a coffee filter revealed a noticeable amount of metal glitter, interpreted as evidence of engine wear/damage from inadequate lubrication | a bolt run for 10 minutes in plain 10W-30 detergent oil retained quite a bit of visible sludge; a second bolt run for 10 minutes after draining off oil and adding an equal 3 oz of diesel (a roughly 1:1 mix, a different ratio than the 1-part-to-4 ratio used in the lubricity test) came out visibly cleaner, described as doing a better job than plain oil at removing sludge | the engine appeared to overheat running on straight diesel and had to be stopped around the 30 minute mark to top off diesel that had evaporated off | lost a couple of PSI on a compression test after the straight-diesel run, described as not a good thing |
How it was tested
- lubricity/film strength test (pure diesel and a diesel/oil mix vs. 10W-30 oil alone)
- safety data sheet review (flash point, boiling point, autoignition temperature)
- small engine no-load RPM test (fixed throttle, disconnected governor) to detect increased internal friction
- post-run filter inspection for metal debris
- sludge cleaning comparison (diesel/oil mix vs. plain oil)
- engine overheating observation during a straight-diesel run
- compression test after the straight-diesel run
“On the lubricity test, it was quite interesting to see that diesel in and of itself is not a very good lubricant. However, when mixed with oil, it does seem to do a decent job. Not a great job, but not a huge loss. So, for the old-timers that recommended adding a little diesel to the oil just before the change, it doesn't seem to be necessarily a bad idea. However, I cannot recommend doing this because anything you add to the crankcase of an engine besides what's meant to go in there has potential to cause damage.”