How can I empirically evaluate the condition of my used motor oil at home?

Question

I changed my oil recently, and my careful scientific observation led me to discover that it was black and a bit runny. Not clear golden like new oil, but neither tarry sludge like a haven't-serviced-it-for-two-years oil. That's essentially my current limit for evaluating the oil condition.

Having read through plenty forum threads on the Longlife oil and the even longer service intervals recommended by my car's manufacturer, I've gathered that the service interval in the car manual probably isn't absolute truth. Every engine seems to end up in slightly different condition, and of course driving habits and environment vary greatly - to me it makes sense to have an empirical guideline on when to change oil.

Blackstone Labs offer the type of services that I'm looking for, but I'm wanting something I can do at home, and for cheap (at least over repeated tests). A few examples I've thought of:

1. Filter to measure mass of foreign particles
2. Spectroscopy to measure change of base compounds
3. Opacity to also measure change of base compounds
4. Phase separation to test for foreign liquids

Though I'm no automotive engineer, so these are all uninformed guesses. Is there such a way to empirically deduce the condition of oil, and thus when to change it?

Answer 1

As a regular user of Blackstone Labs, I believe they use mainly Spectroscopy -- i'm not sure how else they could provide the results they do. I know for a fact that a place in Denver uses infrared spectroscopy as one of their employees has commented about it on forums.

Not sure it's feasible to do this on your own unless you have access to or want to spend a good $20k+ on equipment. But, I'm not an expert / chem engineer.

If your concern is regularly spending money on the test, I might suggest just testing your oil less often in combination with using a passive by-pass oil filtration system. These have many benefits, including prolonging your engine life and saving a lot of money. They are mainly used in diesel applications, but not restricted to the diesel power plant. The reason diesel truck owners use them, is both because it prolongs your engine life, and saves you a lot of money in oil changes. Consider larger commercial vehicles which take tens of gallons of oil and cost hundreds to do a change.

Amsoil is just one company which makes these kits: http://www.amsoil.com/shop/by-product/filters-and-by-pass-systems/by-pass/filters-and-mounts/