Nikasil: Friend or Foe?

Words – Jeff Heywood / Images – BMW Press

BMW E34 540i

To motorists of a certain age, the word Nikasil is as scary as a Siberian labour camp. Back in the ‘90s, engines with Nikasil-coated cylinders suffered excessive bore wear. A batch of petrol was the culprit and it destroyed engines, many of which were built by BMW. The controversy tarnished BMW’s reputation, but quite a few automobile brands suffered cylinder bore wear problems, too. But who or what was to blame exactly?

Nikasil History - Nikasil was a coating introduced by Mahle in 1967. It was initially developed to allow the apex tip seals in Wankel engines (most notably in the NSU Ro80) to work directly against the aluminium rotor housing. Before Mahle’s innovation was implemented, the tips in the rotary engine were renowned for wearing and letting oil pass by the seals. NSU struggled with this issue and it led to VW taking over the brand in 1969, as the compensation claims were crippling the small company.

Mahle’s Nikasil coating allowed aluminium cylinders and pistons to work directly against each other with low wear and little friction. Unlike other methods, including cast iron cylinder liners set into aluminium blocks, Nikasil allowed very large cylinder bores with tight tolerances and thus allowed existing engine designs to be expanded easily.

The aluminium cylinders also gave a much better heat conductivity than cast iron liners, an important attribute for a high-output engine. This is why the coating was further developed as a replacement for hard-chrome plated cylinder bores for Mercury Marine Racing, Kohler Engines, and as a repair replacement for factorychromed snowmobiles, dirt bikes, ATVs, watercraft and automotive V8 bores, and it is still used to this day in top line racing applications; F1 and IndyCar engines use Nikasil extensively.

Suzuki also uses a nickel phosphorussilicon-carbide proprietary coating trademarked SCEM (Suzuki Composite Electro-chemical Material) – a techoogly not dissimilar to Nikasil – to maximize cylinder size and improve heat dissipation in the Hayabusa range of engines, which are also used in automobile and racing installations.

Nikasil is short for Nickel Silicon carbide. Silicon carbide is a very hard ceramic (much harder than steel) that can be dissolved in nickel. The nickel solution can then be electroplated onto the aluminium cylinder bore. The piston

Well known German automotive parts supplier Mahle introduced Nikasil back in 1976, principally to help stop the wear on seal tips in rotary engines, which was a blight on NSU and their excellent, modern looking Ro80, Car of the Year in 1968 but hamstrung by a wonderfully smooth but oil burning Wankel rotary engine…

rings then rub off the exposed nickel, leaving a very hard layer of silicon carbide to prevent the cast iron or steel piston rings from directly contacting the aluminium cylinder. With this setup, the engine tolerances can be much tighter for better performance. The cylinder must be re-plated after it is re-bored, but Nikasil is extremely durable, so the cylinder does not need to be reworked as often as an iron or chrome cylinder.

Porsche started using Nikasil on their 1970 917 race car, and later in the venerable 1973 911 RS. Porsche also used it on production cars, but for a short time switched to Alusil due to cost savings for their base 911s. Nikasil cylinders were always used for the 911 Turbo and RS models. Nikasil-coated aluminium cylinders allowed Porsche to build air-cooled and turbocharged racing engines that had the highest specific output of any engine of their time.

Nikasil became very popular in the 1990s. BMW used it in its straight-six and V8 engines, and it was also used by companies such as Ducati, Jaguar (mostly in its V8 engines) and Moto Guzzi in its then new family of engines.

So who was to blame for the Nikasil debacle?

We’ll stick with BMW for this bit. Nikasil is a manufacturing process that was used by BMW (and others) back in the ‘90s to turn the relatively soft aluminium cylinder bores into a hard wearing surface. This process involved impregnating the bores with a Nickel-Silicone (Nikasil) compound which chemically bonds with the aluminium bore surface. The resultant bore has exceptional wear-resistance, much superior to the standard iron liners used in most BMW engines in the ‘90s. Unlike other bore lining methods, like cast iron cylinder linings, Nikasil also allows car manufacturers to machine larger cylinder bores with tight tolerances, thus allowing existing engine designs to be expanded easily, which is desirable on a cost basis and something we have seen extensively in BMW engines.

Unfortunately, the high sulphur content of some fuels (not necessarily the cheapest – read-on) broke-down the chemical bond resulting in a bore that was essentially machined aluminium. Where this problem occurred, the piston rings would rapidly wear away the cylinder bore to a point where compression was lost. An increase in oil consumption was the first sign that something was wrong, with a hint of blue-smoke from the exhaust a tell-tale sign, especially as the wear got worse.

Over time the engine would then gradually lose power and the smooth running of the engine started to noticeably deteriorate. Once compression was lost, the engine would fail to tick-over smoothly and power-output would significantly reduce. Most noticeably, the car would become very difficult to start as the lack of compression at cranking speeds wouldn’t produce combustion. The cure (as was so often quoted) was to replace the short block, there is no chance of reconditioning the bores. The usual advice was to look out for V8s that rocked at tick-over or that smoked when started.

So was BMW to blame? Well yes and no. The actual wear problem was caused by poor quality fuel with a high sulphur content that was introduced to both the UK and US markets. Europe mostly escaped the Nikasil issue, although there were a small number of Europeanbased BMWs whose engines fell foul of the Nikasil bore wear issue, most likely

One of the biggest casualties of the Nikasil debacle was the M60 V8 engine found in models like the E32 740i seen in this photo

stemming from those visiting the UK on a regular basis unknowingly filling their fuel tanks with high sulphur petrol.

So how did this poor quality petrol enter the UK’s fuel supply? It seems that someone, somewhere (the offending culprit or company has never come to light) had agreed to take a large delivery of oil from South America, which generally has a much higher sulphur content than oil from the Middle East. This oil was then fed into the UK supply system and was received at UK refineries and refined into petrol. The high sulphur content isn’t normally an issue as the sulphur is nearly all removed at the refinery. Unfortunately, the process of removing the sulphur is an expensive one, hence why petrol companies would sooner receive oil from countries that have less sulphurous content.

Now, this is where things get a bit cloak and dagger because no one has officially held up their hands up and admitted that they were responsible for not refining most of the sulphur out of this batch of South American fuel. Instead, the oil was run through the normal refining process reserved for oil from the Middle East, and so petrol with a high sulphur content was introduced into the UK petrol system.

As mentioned earlier, the sulphur reacts with the engine block’s Nikasil lining, damaging the bore walls. Once the lining is damaged, excessive bore wear of the soft underlying alloy occurs very quickly. Some BMW Nikasil-lined engines have failed having covered as little as 30,000 miles.

The Nikasil wear issue first reared its head in the North West of England, where cars that used cheaper supermarket fuel were the first to exhibit problems with the lumpy running engines, followed by a smoky exhaust. People quickly jumped on the bandwagon and blamed cheap supermarket fuel, but then the problem spread as cars which were only refuelled at Shell, BP, Esso, Texaco and other service stations were also developing problems. The reason why the North West was initially blighted by this dirty fuel is that the first batch of the South American oil was refined at Stanlow at Ellesmere Port and then shipped out by tanker to North West petrol stations. The North West malaise then slowly spread to the rest of the UK as the dirty fuel entered the system nationally via other refineries. This didn’t stop the general public and motor trade alike saying it was a North West thing – people would avoid a V8 BMW if the car had lived in the North West – it’s the perfect example of how gossip spreads faster than any plague.

In BMW’s case, the engine most affected was the M60B30 and M60B40, 3.0i and 4.0i V8s. Although some M52B20, M52B25, M52B28 six-cylinder engines also suffered problems. The M60 V8 in both 3-litre and 4-litre guise built between 1993 and 1996 suffered the most. This affected the V8 powered E34 530i and 540i, as well as both the E32 and E38 7 Series 730i and 740i variants, plus a handful of early 840i models equipped with the M60B40 V8.

The M60 V8 was also used by Alpina in the following models at the time, the E34 B10 4.0 and E32 B11 4.0. Alpina also enlarged the M60B40 engine for use in the E36 based B8 4.6 and B10 4.6, but there are no reports of any Alpina engines being replaced, although one would have thought it would have affected Alpina just the same as BMW, seeing as their modified M60 V8s still used the same block.

The M52 issue is a weird kettle of fish; BMW chose to release the engine after the Nikasil issue with the M60 V8 had come to light. One can only assume that BMW thought the Nikasil and high-sulphur-fuel issue was, at the time, exclusive to the US market as American

Even BMWs volume seller the (E36) 3 Series didn’t escape the Nikasil ‘pandemic’ with a small number of 6-cylinder M52 equipped cars like the 323i Saloon in the photo falling victim to high sulphur petrol damage to the engine

Here we have the M60B40 V8 engine seen in the engine bay of an E34 540i, plus a cutaway image showing the M60’s internals. The M60 was particularly prone to Nikasil wear to the cylinder bores…

petrol also has a high sulphur content. The fact that BMW only released an iron block version of the M52 in the US backs up this theory.

As for the M52 bore wear issue in the UK, the M52 single-Vanos version is a little more difficult to break down, as the engine found its way into so many models – E36, E46, E34 and early E39s – yet it affected some but not others. The models with the most problems were the E36 models equipped with the M52 engine. A very small handful of very early in any crisis. The poor owners whose the meaning of precedent; all I can say is E39s also had problems, mainly the cars were no longer covered by BMW’s that I wouldn’t like to explain to someone 520i, 525i and 528i models, whilst also warranty and had decided not to have whose BMW was running an M60 engine affecting a tiny handful of E38 728i’s. their car serviced via the BMW dealer had been refused a replacement when Luckily, most of these cars were under network found that BMW were reluctant that person knew others in a similar warranty and BMW changed the engines to change their failed engine gratis. situation who had been the recipients of as and when required so as not to However, some people who serviced their goodwill from BMW. swamp the dealer network with a blanket cars outside the dealer network were All I would add to the above is that, recall. To this day, BMW will not divulge lucky and BMW replaced their engines as thanks to the good fortune that the world just how many engines it replaced here in a goodwill gesture, while others weren’t wide web was in its infancy, the Nikasil the UK during the Nikasil crisis. so lucky and faced a large bill for a new crisis quickly lost its legs as a story. I

Of course, there are always victims engine. I don’t know what happened to dread to think what it would be like now

It was a shame that BMWs E34 was caught up in the Nikasil debacle, as it was a fine machine. Unfortunately at the time the M60 equipped cars like this wonderful 540i became ‘persona non grata’ in the car world for a time during the 90’s, although a car with a job sheet showing BMW had fitted a new engine had to be a good buy?

with the advent of social media and YouTube.

As for still being nervous about purchasing a BMW running an M60 or M52 engine that could be affected by the Nikasil issue, don’t be. Most, if not all, cars with problems had their engines replaced and I haven’t heard of a car turning up with bore wear issues caused by high sulphur fuel since the controversy in the 1990s. Although I bet someone will prove me wrong after Is this harsh on BMW and others? executive and luxury class has always reading this piece. So the advice I would That’s for you to decide, and if you search been the domain of the big Mercedes give is the same when viewing all used online the debate still carries on to this day. Benz, but thanks to the excellent V8 classic vehicles, Caveat Emptor. Apply For what it’s worth, I do think the engined E34 5er models and the E32 due diligence and if the car uses oil, has a motor industry knows who was at fault 7er, BMW made inroads into the class smoky exhaust or runs like a bag of nails, for this mistake, which allowed millions of traditionally occupied by the Merc walk away unless you’re willing to take on gallons of high sulphur content petrol to E- and S-Class models. Sadly, the the work and repair it. It probably won’t enter both the UK and US national fuel Nikasil issue set it back for a good be a Nikasil issue, but it still might prove supply. I think some kind of under the few years, although the superb E39 5 costly to fix. counter compensation was agreed to Series soon made BMW the darlings

So why did BMW (plus Jaguar etc) cover the cost of replacing the engines of the executive set once again as the cop some of the blame? Well, many have affected, but that’s just a personal view. company switched to Alusil linings in its pointed out that if BMW and its peers In the end, BMW has actually made a engines, which is much more resilient had tested their engines using a mixture very small amount of money supplying against high sulphurous fuel… of different fuel grades, replicating what new engines to those who were refused could end up entering the fuel tank of any goodwill, although the tarnished image it BMW model in all parts of the globe, this gave the company for a while probably We recommend that you always issue would have been discovered and cost them more in the medium term. choose quality fuel and oil for your (hopefully) rectified. The market in the medium to upper BMW.

Nestled in the engine bay of an E36 323i sits an M52B25 2.5i engine. The cutaway pic shows the M52 in all its glory, with the block cutaway exposing the pistons where the damage occurred to the cylinder walls. The M52 wasn’t as badly affected by the ‘rogue’ petrol with high sulphur content like the M60 was, with only a small number of straight-six engines replaced here in the UK. How many is impossible to tell as BMW has never released exact figures…