BLACK DEATH IN ENGINE OIL

What the heck was Black Death?

Black Death first appeared in the early 80's when a sticky black substance was found to be the cause of many engine seizures in Europe. It was extremely frustrating for vehicle owners because dealers and mechanics had no idea what was going on. Black Death just wasn't covered under insurance - if your engine had it, you paid to fix it yourself. 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: 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 it and begin to chemically break down and solidify, leading to the baked-on oil deposits turning gelatinous, like black yoghurt. What doesn't help is that due to packaging, modern engines have smaller sumps than their older counterparts, and so hold less oil. This lower volume of oil can't hold as much crap (for want of a better word) and that can lead to earlier chemical breakdown.
The most common factor in sludge buildup is a combination of mineral oils, a lack of maintenance by the car owner and harsh driving conditions. However, 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 had been having a particularly harsh time with sludge and was 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. Here 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.

Picture credit: Ketchup at the Bimmerfest forums

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 that looks like vanilla yoghurt or mayonnaise. The cap is typically cooler than the rest of the cam case and so the oil/water mix tends to condense there. If the underside of your filler cap has this sort of deposit on it, chances are the engine has 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 gets through the breaks in the head gasket and mixes with the oil. When it gets to the sump it separates out and the oil floats on top. A 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.

Note:

There is one other possible cause for the mayonnaise: a blocked scavenger hose. Most engines have a hose that comes off the cam cover and returns to the engine block somewhere via a vacuum line. This is the scavenger hose that 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) states that you use only VW/Audi recommended oil. 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 almost 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 - over 5,000 in 2008 alone. 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.

CAR ENGINE OIL

How much do you value the engine in your car? The life of your engine depends in no small part on the quality of the oil you put in it - oil is its lifeblood. People typically don't pay much attention to their oil - oil is oil, right? In the bad old days, maybe, but engine oil underwent something of a revolution in the 80's and 90's when hot hatches, 16-valve engines and turbos started to become popular. 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 their GTX mineral oil. This was eventually surpassed by semi-synthetic and fully synthetic oils, including GTX2 and GTX3 Lightec. Those were surpassed by Formula SLX and most recently, Castrol GTX Magnatec. All manufacturers have a similar broad spectrum of oils now - I just mention Castrol in particular as they're my oil of choice for my own cars.

What does my oil actually do?

Your engine oil performs many functions. It stops all the metal surfaces in your engine from grinding together and tearing themselves apart from friction, and it transfers heat away from the combustion cycle. Engine oil must also be able to hold in suspension all the nasty by-products of combustion like silica (silicon oxide) and acids. 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.

If your Mustang heads are in need of repair, check out AmericanMuscle.com

How do I read the numbers around the 'W'? For example 5W40?

As oils heat up, they generally get thinner. Single grade oils get too thin when hot for most modern engines which is where multigrade oil comes in. The idea is simple - use science and physics to prevent the base oil from getting too thin when it gets hot. The number before the 'W' is the 'cold' viscosity rating of the oil, and the number after the 'W' is the 'hot' viscosity rating. So a 5W40 oil is one that behaves like a 5-rated single grade oil when cold, but doesn't thin any more than a 40-rated single grade oil when hot. The lower the 'winter' number (hence the 'W'), the easier the engine will turn over when starting in cold climates. There's more detail on this later in the page under both viscosity, and SAE ratings.

A quick guide to the different grades of oil.

Fully Synthetic	Characteristics
0W-30 0W-40 5W-40	Fuel economy savings Enhances engine performance and power Ensures engine is protected from wear and deposit build-up Ensures good cold starting and quick circulation in freezing temperatures Gets to moving parts of the engine quickly
Semi-synthetic	Characteristics
5W-30 10W-40 15W-40	Better protection Good protection within the first 10 minutes after starting out Roughly three times better at reducing engine wear Increased oil change intervals - don't need to change it quite so often
Mineral	Characteristics
10W-40 15W-40	Basic protection for a variety of engines Oil needs to be changed more often

Motorbike suspension - back end.

Twin-shock, regular swingarm

The classic motorcycle suspension system. An H-shaped swingarm is pivoted at the front to the motorbike frame. On either side there are basic coilover units which provide the suspension. The shocks are inside the coilover units. This is about as basic as you can get on a motorbike and has been around for as long as the motorbike itself. This style of suspension began to fall out of favour in the 80's due to weight considerations and the availability of newer, stronger materials. It was also not a particularly robust design by modern considerations. It all got a bit bendy and flexible under extreme riding conditions, and the only way to make it stronger was to add more metal, which added more unsprung weight, which reduced the efficiency of the suspension.

Monoshock, older style, regular swingarm

In 1977, the first monoshock system appeared to niche markets and racers. It has actually been around in one form or another since the 1930's, but it was only in the early 80's that monoshocks started to appear on production bikes. Monoshock is actually a Yamaha trademark, but it has become synonymous with the design in the same way as people in the UK refer to vacuum cleaners as hoovers. (The Honda version is called Pro-Link). The premise was that manufacturers could save some weight by redesigning the rear suspension and removing one of the coilover units. Monoshocks are still coilovers, but there's only one and it's mounted centrally to the swingarm. On earlier models, the rear swingarm was a sort of basket with a linkage at the top-front. The monoshock sat nearly horizontal in the bike.

Monoshock, newer style, regular swingarm

On the current monoshock designs, there is now a complex linkage at the bottom end which joins the coilover to the swingarm itself, and its important to lube the joints in these linkages regularly. They are very exposed to the elements when riding. The linkage adds leverage to the suspension plus it allows the coilover to be mounted more vertically. Ever in need of less weight (and hence more speed), those clever engineers who devised this variation were able to remove the 'basket' part of the swingarm, and revert to the traditional "H" shaped arm, only with a bit more welding here and there and stronger materials. The popup version of this images also shows a close-up of the linkage.

Monoshock, single-sided swingarm

The ultimate evolution of the monoshock design is the single-sided swingarm. These are super-strong, super-lightweight swingarms like you might find on a VFR800. The advantage of a single-sided system is that the wheel can quickly be taken out and replaced. Not really a huge advantage for you or I fiddling with our bikes at the weekend, but for Moto-GP style racing, it does make a huge difference for the pit crew. Single-sided swingarms need to be pretty heavily engineered because they bear the all the stresses from the rear axle offset to one side. With the traditional double-beam swingarm, the design needs to have longitudinal stiffness to stop it from bending. With the single-sided design, it needs to also have torsional stiffness to stop it from twisting under the offset load. As a result, single-sided swingarms are typically a lot larger and have a huge amount of cross-bracing inside them.

One shock or two? The frothy subject of frappuccino damper oil.

In the good old days, motorbikes had two shock absorbers on the rear of the bike, as shown at the top of this section. As suspension evolved, the dual rear shocks were replaced with a single unit, but the question is why? The answer, it turns out, is pretty simple. In a dual-shock system, the suspension units are typically attached very close to the rear axle. This means that as the suspension compresses and expands, the shock absorber pistons are travelling in a stroke which is nearly the same as the full deflection of the swingarm. Hitting a large bump might deflect the rear axle upwards by 10cm and back, resulting in the same 10cm stroke in the shocks. Do this a lot and the shock absorber piston begins to behave like the plunger in one of those natty little cafetières or milk-frothers - it agitates the damper oil so much and so frequently that the oil begins to heat up and foam or froth. At this point it not only looks like frappuccino foam but it has about the same damping properties too, and thus loses its ability to perform as it should. This is known as fading shock absorbers.
Enter the single shock absorber system mounted towards the front of the rear swingarm. The swingarm might still have a lot of travel at the axle, but basic geometry shows you that closer to the pivot, the deflection is much less. This translates into shorter shock absorber movements which in turn means less opportunity for the damper oil to froth. The ultimate evolution of this is the complex link monoshock system (also shown above), where a complex series of levers reduce the shock absorber travel even further. Typically multi-link setups like this also have some amount of variance in them so that they have a different amount of deflection in the first part of the stroke to the that in the second. This means a single shock absorber unit can respond better to changing road surfaces, soaking up the smaller bumps and shocks with ease and comfort without sacrificing the ability to respond to the occasional mountain or pothole.
As a side note, you'll notice as you read the section on BMW rear suspension below that the monolever and first-generation paralever had a single shock but it was mounted close to the rear axle. This had all the disadvantages of a dual-shock system without any of the advantages of a single-shock system. For the second-generation paralever, the shock was moved closer to the swingarm pivot, thus bringing the design in-line with the small-deflection idea.

The eBay problem

This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject....