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What price do you put on the oil in your car's sump? After all, it is the lifeblood of your car's engine. In the past decade there has been a revolution in car engine oil. All oils are no longer the same. Thanks to the advent of GTi's, 16 valve engines, turbos and the black death, the days of one oil catering for everyone are 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 will 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).
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 (and that's the last thing we'd want!). But it also has to dissipate the heat generated from this friction too. It also transfers heat away from the combustion cycle. Another function is that a good engine oil must be able to hold in suspension the nasty by-products of fuel combustion, such as silica (silicon oxide) and acids, whilst also cleaning the engine of such nasties. And it must do all of these things under tremendous heat and pressure without succombing to fatigue or black death, the ultimate engine destroyer.
Mineral or synthetic?Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils have zero mineral oil content and are entirely concocted by chemists wearing white lab coats in oil company laboratories. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.A couple of words of warning:
Flushing oilsThese are special compound oils that are very, very thin. They almost have the consistency of tap water when cold. Typically they are 0W/20 oils. Don't ever drive with these oils in the engine - it won't last. Their purpose is for cleaning out all the gunk which builds up inside an engine. To use them, drain your engine of all it's oil, but leave the old oil filter in place. Next fill it up with flushing oil and run it at a fast idle for about 20 minutes. Finally, drain all this off (and marvel at the crap that comes out with it), replace the oil filter, refill with a good synthetic oil and voila! Clean engine.Of course, like most things nowadays, there's a condition attached when using flushing oils. In an old engine you really don't want to remove all the deposits. Some of these deposits help seal rings, lifters and even some of the flanges between the heads, covers, pan and the block, where the gaskets are thin. I have heard of engines with over 280,000km that worked fine, but when flushed it failed in a month because the blow-by past the scraper ring(now really clean)contaminated the oil and screwed the rod bearings.
So what should I buy?Quality Counts! It doesn't matter what sort of fancy marketing goes into an engine oil, how many naked babes smear it all over their bodies, how bright and colourful the packaging is, it's what's written on the packaging which counts. Specifications and approvals are everything. There are two established testing bodies. The API (American Petroleum Institute), and the European counterpart, the ACEA (Association des Constructeurs Europeens d'Automobiles - which was the CCMC). You've probably never heard of either of them, but their stamp of approval will be seen on the side of every reputable can of engine oil.
If this is all confusing you, then rest assured that all top oils safely conform to the current standards. What you should treat with caution are the real cheapies and those with nothing but a maker's name on the pack. Anything below about £12 ($18) for 5 litres just isn't going to be worth it. Grade counts too!The API/ACEA ratings only refer to an oil's quality. For grade, you need to look at the SAE (Society of Automotive Engineers) ratings. These describe the oil's function and viscosity standard. Viscosity means the substance and clinging properties of the lubricant. When cold, oil can become like treacle so it is important that any lube is kept as thin as possible. It's cold performance is denoted by the letter 'W', meaning 'winter'. At the other end of the scale, a scorching hot oil can be as thin as water and about as useful too. So it needs to be as thick as possible when warm. Thin when cold but thick when warm? That's where MultiGrade oil comes in. For ages, good old 20W/50 was the oil to have. But as engines progressed and tolerances decreased, a lighter, thinner oil was required, especially when cold. Thus 15W/50, 15W/40 and even 15W/30 oils are now commonplace. Synthetics can go down as far as 5W which seemed unbeatable until Castrol came up with SLX - a 0W30 formulation! 'Free flowing' just doesn't describe it! It's predominantly a workshop oil retailing at around £10 ($15) a litre, but recommended for use in places like Canada in the winter. The latest offering to this 0W30 engineering miracle comes from AMSOIL. So again: what should I buy? That all depends on your car, your pocket and how you intend to drive and service the car. All brands claim theirs offers the best protection available - until they launch a superior alternative. It's like washing powders - whiter than white until new Super-Nukem-Dazzo comes out. For most motorists and most cars, a quality mainline oil is the best. Ones which are known to be good at their job. Stuff like Castrol GTX. They're not too dear either. Don't believe the sales hype - they all perform to the same standards once they're out of the can and into your engine. Moving up a step, you could look at Duckhams QXR and Catrol Protection Plus and GTX3 Lightec. The latter two of these are designed specifically for engines with catalytic converters. They're also a good choice for GTi's and turbo'd engines. Go up a step again and you're looking at synthetic oils aimed squarely at the performance market. To get more money out of you, the manufacturers sell this stuff in smaller amounts which makes an oil change more expensive.
Viscosity and Viscosity Index (VI).The proper viscosity is the single most important criteria of a lubricating oil. The basic performance of machinery is based on the viscosity of the lubricant. Viscosity is, if you like, the resistance to the flowability of the oil. The thicker an oil, the higher its viscosity. The chart on the right shows a rough guide to ambient temperatures vs oil viscosity performance in both multigrade (top half) and single grade (lower half) oils.Multigrade oils work by having a polymer added to a light base oil which prevents the oil from thinning too much as it warms up. At low temperatures, the polymers are coiled up and allow the oil to flow as it's low number (W number) indicates. As the oil heats up, the polymers unwind into long chains which prevent the oil from thinning as much as it normally would. The result is that at 100°C, the oil has thinned only as much as it's higher rating. Think of it like this: a 10W30 oil is a 10-weight oil that will not thin more than a 30-weight oil when it gets hot. The viscosity index of a lubricant is an empirical formula that allows the change in viscosity in the presence of heat to be calculated. This tells the user how much the oil will thin when it is subjected to heat. The higher the viscosity index, the less an oil will thin at a specified temperature. Multi-viscosity motor oils will have a viscosity index well over 100, while single viscosity motor oils and most industrial oils will have a VI of about 100 or less.
What about own-brands?If you can't afford the big-name players, you could look at own-brand oils. These are usually badged oils from one of the larger companies but sold without the name, they are cheaper. Check the standards and grade ratings on the pack first!!! And just make sure it isn't a 20W/50 oil (which a lot are because it's cheap) unless your car is old enough to warrant it.
Servicing and checkingFor God's sake don't skimp on either of these. You can never check your engine oil too often. Use the dipstick - that's what it's there for - and don't run below the 'min' mark. Below that, there isn't enough oil for the pump to be able to supply the top of the engine whilst keeping a reserve in the sump. All oils, no matter what their type, are made of long-chained molecules which get sheared into shorter chains in a running engine. This in turn means that the oil begins to lose it's viscosity over time, and it uses up the additives in it that prevent scuffing between cams and followers, rings and cylinder walls etc etc. When this happens, fresh oil is the key. And don't worry about the engine oil turning black. It will lose it's golden-brown colour within a few hundred miles of being put in to the engine. That doesn't mean it's not working. Quite the contrary - it means it is working well. It changes colour as it traps oxidised oil, clots and the flakes of metal that pop off heavily loaded engine parts. Just don't leave it too long between oil changes.So how often should I change my oil?You can never change your engine oil too frequently. The more you do it, the longer the engine will last. The whole debate about exactly when you change your oil is somewhat of a grey area. Manufacturers tell you every 10,000 miles or so. Your mate with a classic car tells you every 3,000 miles. Ole' Bob with the bad breath who drives a truck tells you he's never once changed the oil in his car. Fact is, large quantities of water are produced by the normal combustion process and, depending on engine wear, some of it gets into the crank case. If you have a good crank case breathing system it gets removed from there PDQ, but even so, in cold weather a lot of condensation will take place. This is bad enough in itself, since water is not noted for its lubrication qualities in an engine, but even worse, that water disolves any nitrates formed during the combustion process. If my memory of chemistry serves me right, that leaves you with a mixture of Nitric (HNO3) and Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance travelled is probably one of the least important in most cases. Here is my selection in rough order of importance:
Dammit Chris, get to the point already!Hang on a tic - if you really want the answer, there's a couple more factors you need to take account of: Crank-case scavenging (that's the clever term for sucking the nasty fumes back out of the crank-case) - or lack of it - is a crucial multiplying factor affecting all the other items listed above. As an example, the worst I've heard of was a Ford Fiesta of the mid 70s or so. It's crank-case fume extraction was via a tiny orifice directly into the inlet manifold which obviously could not handle any significant volume of crank-case fumes without upsetting the carburation. The car in question had been used almost exclusively for 5 mile journeys to/from work, shopping etc, and it had always been serviced "by the book". Despite (or because of) this, the engine was totally buggered at 40,000 miles. Alternatively you might get a car that by virtue of excellent crank case fume scavenging could tolerate many more cold starts than one without.Taking all these into consideration, my philosophy would be to totally ignore the distance and change the oil three times a year - about November, February and May. Move these dates a bit according to the severity of the winter. An average family car will do around 14,000 miles per year and about 2/3 of that will fall in the May - November period. At the end of that period, the car will have just about touched on the recommended oil change distance - but all done at reasonable temperatures and including long distance runs during vacations and good weather. During the Nov - Feb. period it may acumulate only 2 or 3 thousand miles, all low temperature starts and mostly short runs. The Feb. to May period is likely to be about the same. About 10 or 15 years ago, an article in the ANWB journal (ANWB is the Dutch equivalent of the AA) reached more or less the same conclusion that distance was not very important. In their case they applied this to their road service fleet, which typically once started in the morning never got cold. In effect, they hardly ever changed the oil! I seem to remember 30,000 miles between oil changes being quoted. I also seem to remember that they had some kind of water or acid indicator attached to the end of the dipstick and went by that rather than distance. That's a politician's answer - you've dodged the entire issue!Have I? I don't know how far you drive in a year, where you live, the style of your driving or anything else so I can't tell you what's right for your car. Personally, I change the oil and filter in my 1985 Audi Coupe every 5,000 miles. It's done over 150,000 miles, doesn't leak and doesn't consume any oil. If you must have a figure from me, then 5,000 is it.
What else happens when I change the oil then?Engines pump about 10,000 litres of air for every litre of fuel consumed, and along with all that air, they suck in plenty of dirt and grit. A good air filter will stop everything bigger than a micron in diameter - everything smaller mostly just floats around harmlessly in the 0.001inch minimum thickness oil films that separate all the moving parts. Despite all of this, there will always be submicron particles that get in and there will be places in the engines oilways where they will gather. Every time you empty the oil from your sump, you're also draining this fine grit with it.
And so to engine additivesThink what you will of these. Whatever you call them, they are an addition to the engine which it was not designed to take. Engines are designed to use engine oil, not Teflon®. Make up your own mind - read this report and see what you think. In my opinion they are primarily a placebo to put your mind at rest but spend their time clogging up your engine and throwing all the tolerances out of whack.
Slick 50 in $20M lawsuitBlue Corral, the manufacturers of the Slick 50 engine oil additive, have been banned by a Federal Commission from making claims about reduced engine wear, increased fuel economy and lower running temperatures in it's advertising in America. The Federal Commission found the company's claims of increased performance and reduced wear were unsubstantiated, and Blue Corral has agreed to pay upwards of $20M in damages to affected customers.Source: Max Power magazine, March 1998
ProLong in troubleThe manufacturers of the ProLong engine additive have been dealt a smack in the face by a Consumer Reports Magazine report into their product. CR attempted to reproduce the "no oil" test where all the oil was drained out of an engine which had been treated with ProLong, and then the engine was run. CR managed a maximum of 13 seconds running out of each of two engine before they seized up, welding the pistons to the barrels. The case is being brought to a Federal Commision for prosecution for false advertising claims. You can subscribe to the online version of Consumer Reports here for a minimal fee, and read all about it in their October 1998 features.Source: Consumer Reports, October 1998
DuraLube dealt a crippling blow.The manufacturers of the DuraLube engine additive have also been dealt a smack in the face by a Car & Driver Magazine report into their product. C&D; tried the same tests as Consumer Reports did on ProLong, and had similar results, but in a much quicker time. The C&D; engines lasted a staggering 11 seconds without oil. You do the math. The Federal Commission has been handed the details and are 'processing' it.
My personal views on additives:Apart from the fact that the big 3 manufacturers are all in trouble (see above):My views on engine oil additives are this: the oil companies spend billions on research and development in order to make their oils suitable for use in car engines. A standard off-the-shelf engine oil is already stuffed with a cocktail of additives put there by the oil company. By contrast, additive companies spend a couple of million on R&D and then claim that their product (and only their product) will enhance the life of your engine. You're adding an unapproved additive to an already additive-full oil. Spot the problem? The current trend is the "90% of your engine wear happens at startup" advertising ploy. This fact is absolutely true, but as it happens, it's less to to with "grinding engine parts" and more to do with combustion. When the combustion gases burn, they form acids which are highly corrosive when their vapours condense. These acids collect in the upper cylinder areas where their temperature is raised above their dew point. The acids condense and etch the cylinder walls and piston rings. In reality, this accounts for over 85% of engine wear, the other 15% being down to abrasion. So the adverts are nearly right - most of the engine wear does happen at startup, and it is because of a lack of oil, but it isn't because the oil isn't coating moving parts - it's because it's not transporting these acidic gases away. Having said that, if you start the engine and let it idle for 15 seconds or so before moving off, you can probably add another 100,000 miles to your engine's life without one bottle of additive. This warms the oil up a tad and makes sure it's in all the most vital areas before you start putting a strain on the engine. Most handbooks tell you not to let the engine warm up before driving off (they're referring to the acid corrosion mentioned above), but they mean don't let it reach working temperature. If, however, you insist on starting up and belting off down the road, think of this next time: it takes an average engine around 3 minutes of average driving for the exhaust manifold to reach 300°C. If you blast off and run around at full throttle, right from the word go, that process takes a little under a minute. Think about it - from outside air temperature to 300°C in a minute - what exactly is that doing to the metal in your manifold? Ask anyone who's ever owned an original Audi Quattro - they'll tell you exactly what happens. I'm not saying that these companies are having us all on, heaven knows there are plenty of statements from companies and private individuals who have reportedly reaped the benefits of these products. But in my experience, it's simply not worth the huge risk of putting the additive in there.
Another perspective:I received this email from Albert Clark who has, it seems, had first-hand experience of one of the additive products:I kept hearing about such a product and found a store going out of business that was practically giving it away. I put a quart in two cars: An MGB and a Chevy 305 V-8. The MGB went 20 miles before a ring stuck causing it to start throwing oil everywhere. A mechanic then messed up when putting new pistons on the old rods and shortly after rebuild a piston froze and threw a rod bearing that ruined the crank, etc. The Chevy started using a quart every 25 miles immediately after the product was used. I drained it and refilled immediately, but it took engine flush and about 4 oil changes over 2000 miles before oil usage was reduced to a quart every 400 miles. It was using a quart every 800 miles before that. I ended up putting another 60,000 miles for a total of 180,000 miles before rebuild. I will never recommend such a product to anyone. To give you an final example: my Audi Coupe was suffering from some horrendous idling problems because of a coked-up throttle butterfly. Having fallen prey to the marketing hype, I added some decoker to the fuel in order to shift it and it had bugger-all effect. So one weekend, I bought a spray can of carb' cleaner (about 3 pounds UK, $1.70 US) and took the throttle body apart on the fuel injection system. I sprayed a bit of cleaner in and wiped it around carefully with some tissue paper. All the coke came off in one go and when I bolted the throttle body back on and started the engine, it idled perfectly first time. The moral? If you're going to care for your engine, do it properly, not in half-measures, and it will look after you for as many miles as you care to drive.
What about Ionically Charge Oil Particles?Pardon? Sounds like something out of Star Trek doesn't it? Well there's an increasing trend in the industry now to try something a little different. It seems that a couple of the big players are now experimenting with charge oil molecules which attract themselves to engine parts with no other additives. The idea is, to simplify it, magnetic oil. The oil sticks to the engine parts when the engine is turned off, and is theoretically still there, ready to protect, when you next turn the engine on. The first big player on the scene with this was Burmah Castrol with their Castrol Magnatec oil. Theoretically, this type of product is a far safer bet than an additive, and so far I've heard nothing but glowing reports about it. But just stop and think for a moment - why have these companies now decided to go this route? Are they admitting that the older additives with suspended solids in them were perhaps not such a miracle after all?
Finally, and just as importantly: Disposing of used engine oil.Think about it for a minute. What did you do with that last oil change? Pour it away down a drain? Seal it and bin it? The annual average for oil which is just washed away is 720Million gallons! About 120Million of that is from tanker spills which leaves another 600Million from domestic and business disposal. This all ends up polluting the groundwater.So what can you do? Well, you can dispose of your used oil properly. Firstly, it's worth noting that engine oils which have been used are mildly carcinogenic. This means cancer, specifically skin cancer. To be safe, wash any off quickly with a degreaser like GUNK. For heavens sake, don't use petrol (gasoline) - most fuels contain long chain hydrocarbons, which when exposed to skin pass right through to the blood stream. (This can mean liver damage, and possibly failure) Better still, wear protective gloves. Once the oil is drained into a suitable container, try your local garage. All garage workshops must have disposal barrels and many will allow you to dump your oil into their barrels. In the UK, many DIY superstores now have oil disposal banks where you can empty your used oil, and it's collected every couple of days by a tanker. So next time, just think about first. If only for the fact that in most civilised countries, it's actually an arrestable offence to dispose of oil in the public sewerage system. If you live in the UK, phone 0800 663366 to find the location of your nearest oil bank.
A CHEAP ENGINE OIL MAY SAVE YOU MONEY IN THE SHORT TERM, BUT IT WILL COST YOU IN THE LONG TERM! DON'T SKIMP!
More than you ever wanted to know about motor oil (Ed Hackett):
Links to engine-oil related companiesOther linksUK Jaguars.
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The Engine Oil Bible Awards and mentions So That's where the road tax goes! Car modifications we could do without An Open Letter to the UK Government
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since 12th August 1996
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