Oil, Winter and Waxes...

[Dave Longley]

It's definitely not winter but I've got a oil related winter type question.
Was just reading 'Motor Oil' by A E Haas and in one of the sections he mentions "oils form waxes in icy cold weather". Anyone know if this occurs even if the engine isn't run? For example, when putting a car up for the winter many of us change the oil just before hibernation (the car). Some advocate changing the oil again before taking it out come spring. What do you think about this? Anyone done a UAO on oil that's been sitting in the car all winter and compared results to the VOA?
Three questions is enough already. Thanks for your patience. Cheers, Dave

 

[Curious Kid]

Oil whose basestock is derived from crude petroleum, even having gone through dewaxing processes, still contains some wax. When it gets cold enough, wax crystals will start to develope and cause the oil to begin to appear cloudy. At this temperature, this is what is deemed the "cloud point" for the oil. If the temperature drops enough, individual wax crystals will start to form a matrix, much like frost on glass, causing rapid thickening. An additive is used with these types of lubricants to further lower the point at which wax crystals cause solidification. Warming after solidification will enable the oil to turn back to "normal."

Experiment - Take a sample of clear lamp oil and put it in the freezer. After some time, take it out and observe the white solid mass. Leave it out on the counter and observe how it melts over time.

The short of it...Yes this goes on where ever such petroleum oil is able to get cold enough. Changing of the oil I believe is to remove potential acids and particulate matter that may settle out during the storage period. Having any acids and other blow-by by-products acting as free radicals, speeds up oxidation of the oil. Preventative maintenace in an effort to reduce sludge and varnish build-up potential, would lead one to change out the oil I gather.

As far as changing the oil out in the spring, well though there has been some residual used oil in the case when adding the fresh oil, I don't feela passing of months would make much of an impact. If cold weather was experienced over the storage period, this alone has a slowing effect upon lube oxidation. I guess that means I don't think changing again is neccessary, but let's see what others have to say.

As for myself (seeing as low as -20 deg. F during the winter), I change the oil in the spring time for all the lawn equipment as well as the motorcycles I once owned. Is this the best way of doing it, I really don't know, but haven't seemed to have had any oil related problems to speak of thus far, knowingly that is.

With that last bit, I admit to not having any UOA's to compair with any VOA's, so others will hopefully chime in with proof.

Take care.

 

[Blue99]

quote:

---

Was just reading 'Motor Oil' by A E Haas and in one of the sections he mentions "oils form waxes in icy cold weather".

---

With all due respect to Dr. Haas, as he is a site sponsor, some of his earlier statements are no doubt being revised.

All dino base oils are subjected to a de-waxing process. Grp II, II+ and III undergo either a catalytic or a hydro dewaxing process. The larger waxy hydrocarbon chain molecules are either removed or broken down.

While this statement may have been true with solvent refined & dewaxed base oils prior to 1990, it is not a factor with today's GF-4 oils.

Most of us, who actually live north of Florida & deal with sub 0F or -18C temperatures, are more concerned with the ASTM-D5293 cold crank rating, or the ASTM-D4684 low temperature pumping rating, not the "wax bogeyman"!

 

[Ken2]

Petroleum oils contain a pour point depressant that keeps the very small amount of remaining wax from making the oil too viscous when very cold. The oils are good for the temperatures recommended for that oil. I'd run the new Fall oil.

AEHaas writes a good story, but sometimes his facts are muddled.


Ken