The car maintenance Bibles

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The engine oil Bible







How much do you value the engine in your car? Think about it, because
the life of your engine depends in no small part on the quality of the
oil you put in it - oil is the lifeblood of your car's engine. From the
mid 80's for 8 or 9 years there was a veritable revolution in car
engine oil. All oils were no longer the same thanks to the popularity
of hot hatches, 16-valve engines and turbos as the tuner scene started
to rise. Combined with the devastating problems of black death, the days of one oil catering for everyone were over.
Take Castrol for example. They led the field for years with GTX. This
was surpassed a few years back by semi-synthetic and fully synthetic
oils, including GTX2 and GTX3 Lightec. Now, that's been surpassed by
Formula SLX which can cost upwards of £50 ($75) for 5 litres. And most
recently, Castrol GTX Magnatec which is muscling in on the hitherto
separate world of friction reducers (and we'll deal with them later, on
the additives page.).


What does my oil actually do?




An engine oil's job is primarily to stop all the metal surfaces in your
engine from grinding together and tearing themselves apart from
friction whilst transferring heat away from the combustion cycle.
Engine oil must also be able to hold all the nasty by-products of
combustion, such as silica (silicon oxide) and acids in suspension. It
cleans the engine of these chemicals and build-ups, and keeps the
moving parts coated in oil. Finally, engine oil minimises the exposure
to oxygen and thus oxidation at higher temperatures. It does all of
these things under tremendous heat and pressure.


What the heck was Black Death?




Black Death first appeared in the early 80's when a horrible sticky
black substance was found to be the cause of many engine seizures in
Europe. Many engines were affected but Ford and Vauxhall (GM) suffered
the most. Faster roads, higher under-hood temperatures, tighter
engineering tolerances and overworked engine oils turned out to be
contributors to the problem. The oils just couldn't handle it and
changed their chemical makeup under pressure into a sort of tar-like
glue. This blocked all the oil channels in the engines, starved them of
lubrication and caused them to seize. I don't recommend this but you
can reproduce the effect with a frying pan, cooking oil and a
blowtorch. The cooking oil will heat up far quicker than it's designed
to and will turn to a sticky black tar in your pan. Either that or it
will set fire to your kitchen, which is why I said "don't do this".
Anyway, burning kitchens aside, Black Death was the catalyst for the
production of newer higher quality oils, many of them man-made rather
than mineral-based.


Black death for the 21^st century





There's a snappy new moniker for Black Death now, and it's called
sludge. The cause is the same as Black Death and it seems to be
regardless of maintenance or mileage. The chemical compounds in engine
oils break down over time due to prolonged exposure to high
temperatures and poor maintenance habits. When the oil oxidises, the
additives separate from the oil and begin to chemically break down and
solidify, leading to the baked-on oil deposits turning gelatinous, and
that nasty compound is what is lovingly referred to nowadays as sludge.
It's like black yoghurt. What doesn't help is that modern engines, due
to packaging, have smaller sumps than in the "good old days" and so
hold less oil. This means that the oil that is present in the engine
can't hold as much crap (for want of a better word) and can lead to
earlier chemical breakdown.
The most common factor in sludge buildup is mineral oils combined with
a lack of maintenance by the car owner combined with harsh driving
conditions. But this isn't true in all
cases. For some reason, a 2005 Consumer Reports article discovered that
some engines from Audi, Chrysler, Saab, Toyota, and Volkswagen appear
prone to sludge almost no matter how often the oil is changed.
What does sludge look like?




I was contacted by a BMW driver who's been having a particularly harsh time with sludge and has been discussing it on the Bimmerfest forums.
He posted some images of his problem and other readers posted
similarly-framed images of the same engine components in "normal"
condition. Below are two of those photos. On the left is what the cam
case should look like in a well maintained engine when photographed
through the oil filler cap. On the right is what the same type of
engine looks like when suffering sludge buildup.



In this example, the consensus was that the sludge buildup was caused
by an overheating engine, oil that hadn't been changed for 20,000 miles
of stop-go city driving, a lot of cold starts and a period of about 12
months in storage without an oil change. Most of this happened before
the current owner got it.

Curing sludge



There are no hard
and fast rules for curing an engine of sludge buildup. If it's really
bad, flushing the engine might be the only cure, but that could also
cause even more problems. If flushing the engine results in bits of
sludge getting lodged where they can do more damage, you're actually
worse off.
It's interesting to note that some race techs have reported sludge buildup in race engines as a result of aftermarket additives
being used in conjunction with the regular oil. The chemical
composition of the additives isn't as neutral as some companies would
lead us to believe, and combined with particular types of oil and
high-stress driving, they can cause oil breakdown and sludge to appear.
The lesson from them appears to be "don't use additives".

When is sludge not sludge?





Easy. When it's an oil and water emulsion from a leaking or blown head gasket.
If this happens, you get a whitish cream coloured sludge on the inside
of the oil filler cap. The filler cap is typically cooler than the rest
of the cam case and so the oil/water mix tends to condense there. So if
you take the oil filler cap off and it looks like it's covered in
vanilla yoghurt or mayonnaise, you've got a blown head gasket. A
surefire way to confirm this is if your oil level is going up and your
coolant level is going down. The coolant is getting through the breaks
in the head gasket and mixing with the oil. When it gets to the sump it
separates out and the oil floats on top. A slightly more accurate way
to check for this condition is to use a combustion leak tester, or
block tester. If you're in America, NAPA sell them for about $45 (part #BK 7001006). If you're in England, Sealey sell them for about £70 (model number VS0061).
Combustion leak testers are basically a turkey baster filled with PH
liquid, with a non-return valve at the bottom. To use one, run your
engine for a few minutes until its warm (not hot) then turn it off. Use
a protective glove (like an oven glove) and take the radiator or
reservoir cap off. Plug the bottom of the combustion leak tester into
the hole and squeeze the rubber bulb on top. It will suck air from the
top of the coolant through the non-return valve and bubble it through
the PH liquid. If the liquid changes colour (normally blue to yellow),
it means there is combustion gas in the coolant, which means a head
gasket leak.
There is one other possible cause for this yellow goop
: a blocked scavenger hose. Most engines have a hose which comes off
the cam cover and returns to the engine block somewhere via a vacuum
line. This is the scavenger hose which scavenges oil vapour and gasses
that build up in the cam cover. If it's blocked you can end up with a
buildup of condensation inside the cam cover, which can manifest itself
as the yellow goop inside the filler cap.

VW / Audi sludge problems




While the the 1.8T engines in Audi A4's, Audi TT, VW Passat, Jetta, Golf, New Bettle, are all very prone to sludge build-up, Audi/VW does not
have an extended warranty for them from the factory. The factory
warranty is 4 year/50,000 miles but it can be extended if purchased.
Although Audi/VW now has 10,000 mile service intervals, oil changes can
be done between "services", and should be done if the vehicle is driven
in heavy traffic, offroad, and non-highway use. Also, Audi/ VW will only warrant an engine if the customer has proof of all their oil changes. As of 2004 I belive all 1.8T engines must use synthetic oil.
So if you own one of these sludge-prone engines, what can you do?
Obviously, Volkswagen Audi Group (VAG) recommends that you use only
VW/AUDI recommended oil which at the time of writing is Castrol Syntec
5W-40. You should also keep up on your oil changes, making them more
frequent if you drive hard or haul a lot of cargo. The most important
thing for the VW or Audi owner is this: if the oil light comes on and beeps the high pitch beep that most everyone ignores, pull over and shut the engine down immediately.
Many VAG engines can be saved by this procedure. Have the vehicled
towed to a VAG dealer. Their standard procedure is to inspect the cam
bearings; if they're not scored, the oil pan will be removed and
cleaned out and all the crankcase breather hoses and the oil pickup
tube will be replaced. They'll do an oil pressure test with a
mechanical gauge, and hopefully will also replace the turbo lines.
Finally, the turbo will be checked for bearing free-play. The VAG
turbos run really hot even with proper oil and coolant supply - that's
why you need a good quality synthetic in them.

Toyota sludge problems



For
their part, Toyota have the dubious honour of having the most
complaints about sludge buildup in their engines - 3,400 at the last
count. At the time of writing there is a class action suit going on
against them. Details can be found at www.oilgelsettlement.com


Saab sludge problems




For an example of sludge in a Saab 9 5 Aero with only 42,000 miles on
it, you might be interested to read my case study on this engine, put
together with the help of a reader. Our sludge case study.