Mike: I doubt they add wax to the oil. Here's a copy of a post I lifted in ford-trucks.com; a site I frequent (super site if you own a Ford truck). Read on:
A letter sent to Quacker State:
Through out the net, there are many recommendations AGAINST using
Pennzoil, and Quaker State motor oils in automobiles because they are
parafin based. These parafins cause sludge build-up in automobile
engines more so than motor oils with ash bases. Your response?
Their response was:
Thanks for your e-mail.
First of all, every engine oil made today that is API SD, SE, SF, SG,
SH, SJ or SL rated is made from paraffinic base stocks. This holds true
for Pennzoil, Quaker State, Valvoline, Havoline, Mobil,
Castrol, etc.
As far as forming sludge deposits -- no API SJ or SL rated motor oil will
form deposits unless an underlying factor is present. Usually there are
only a few ways to form sludge, such as:
Not changing oil & filter often enough for the type of service
A coolant leak into the crankcase through a leaky
head gasket or cracked block
A malfunctioning or plugged up PCV valve or hose
Paraffinic base oils refers to the type (i.e., structure and shape) of
the oil used. Paraffinic oils provide the best resistance to chemical
attack, change little in viscosity when the temperatures change, and
are the most resistant to form sludge and varnish. Other base oils, like
napthenics and aromatics, are not used in any high quality motor oils
made today. Please see below for a detailed explanation of paraffinic
base oils.
Paraffin: It's Not What You Think
One of the most misunderstood components of a finished lubricant
product, from a consumer's viewpoint, is the role of paraffins in a
paraffinic base stock. Base stock is the base lubricating fluid into
which performance additives are added to produce a finished lubricant
product. A base stock is usually extracted from petroleum crude or
selected synthetic material. Paraffin base stocks originate from
petroleum crude oils.
What is a paraffin?
A paraffin is a molecule composed of hydrogen and carbon
atoms(hydrocarbon) arranged in straight or branched carbon chains.
Paraffins have excellent oxidation stability properties. This means that
paraffinic base oils are the oils of choice for high temperature
applications because they have excellent resistance to the chemical
reaction between heat and air.
Because paraffin base oils do contain wax, they usually have poor low
temperature properties compared to other types of base
oils. This problem is easily solved by removing most if not all of the
straight chain paraffins by a dewaxing process followed by the
addition of special additives called pour point depressants that give
paraffin based lubricants excellent low temperature performance.
There is a myth that paraffins cause sludge deposits. This is not the
case. The fact is, engine sludge is caused by partially burnt fuel,
water and other contaminants that find their way into the crankcase
during stop and go driving (this can appear as a white or tannish
colored emulsion in the cooler parts of the engine like valve covers, oil
filler tubes or underside of oil filler cap).
In addition to high oxidation stability, natural high Viscosity Index (VI)
of paraffin base oils makes them very desirable for use in high quality
passenger car motor oils. All liquids have a tendency to become
thinner as more heat is applied them. An oil's viscosity index is its
ability to resist change in viscosity with respect to temperature. The
higher the VI of an oil, the lower is its tendency to change viscosity
(become thinner) as it heats up. This is very important when it comes
to proper lubrication of an engine.
Often when a mechanic tears down an engine and sees the presence
of sludge deposits, he/she will automatically point to the oil and
paraffins as the root cause of the sludge problem. In doing so, the
mechanic may forget to review the service history of the vehicle. An
engine which has a sludge deposit problem is often a engine which
was driven in severe service conditions and who's owner neglected to
keep his/her vehicle properly maintained, such as by extending the oil
drain interval, a malfunctioning PCV system or plugged valve, or a
leaky head gasket which allows ethylene glycol to enter the
crankcase. Extending the oil drain interval beyond the manufacturer's
recommendations allows contaminants to accumulate. Eventually, this
build up of deposits will plug oil lines, galleys and
screens. This, in turn, helps accelerate the wear of engine parts.
In conclusion, paraffin base oils are not an engine's nemy. They
are actually one of an engine's best friends. The enemy is extreme
driving conditions and/or neglect of proper maintenance, among other
things. Any myth that paraffin causes sludge is just that, a myth.
Thanks again for your e-mail inquiry and have a good weekend.
Sincerely,
Grant Weidler
Pennzoil-Quaker State Company
Lubricants Technology
Technical Services Representative
(800) 458-4998