Automotive Fluids - Lubricating Oils & Greases, Fuels, Coolants & Brake Fluids

KEW Engineering




How does Oil Protect?

Base Oils Explained

Oil Aging & Degradation

Additive Formulations

Oil Viscosity Explained

Oil Quality Ratings

FAQs on Motor Oils


Brake & Clutch Fluids




Disposal of Used Oils




Copyright 2009

KEW Engineering Ltd


For NORMAL driving is it worth the added expense of using semi-synthetic or synthetic oils in my modern car?

I do occasional track days, too, in my car what should I use?

Are frequent oil changes better?

What type of oil does the factory use?

Why does my oil go black just after I change it?

My engine is modified, should I deal with it differently?

Should I keep this oil in until the next service schedule and just top it up for now?  In another words, can I mix oils?

Why is Idling bad for my engine?

Running in a new Engine

Switching to a Synthetic on new and used cars

How long can I store Oil?

I would like to know whether for NORMAL driving itís worth the added expense of using semi-synthetic or synthetic oils in my modern car?

If you plan to keep your car for more than 5 years then go for best you can afford. That means synthetic, not semi-synthetic.


For an intended ownership of 3 years or 60k miles operation, use what's recommended and then let the next owner worry about it.


Seriously, if you plan to maintain a Full Service History by having a dealer service for a 3yr/60k ownership, then let the dealer put in what they offer; it should be the approved oil.  That said, I know one owner of a dealer-serviced prestige German car was dumbfounded after 100k miles and 6 yrs to find the pick-up strainer blocked with sludge.  Something is seriously wrong there and one suspects that cheap oil was used but expensive oil paid for in the servicing bill.


Going for fully synthetic will mean dumping oil at 12 to 15k miles depending on your service schedule, but that oil may still be good for another 10k if you do a lot of motorway miles at legal speeds. The upside is that if you plan to run the car for the next ten years then buy the fully synthetic, it will help ensure optimum oil performance between services.  Donít forget to use good quality fuel to keep the injectors and engine clean.

I donít like to be drawn into recommending brands so donít ask.


I do occasional track days, too, in my car what should I use?

There are a couple of other smaller specialist oil manufacturers who use purer base stocks that are less susceptible to shearing and provide greater film strength. These are proven case studies, the motorsport people use names like Motul, Redline and Royal Purple and independent assessment has shown better wear protection than even some of the best major brand oils.

On a classic it may pay of course to just change the oil before and after that track day session.


Are frequent oil changes better?

Many people still believe that frequent oil changes are the best way to look after an engine, which is true up to a point if you do the oil change while the oil is still warm as it drains out more of the solids and wear debris material from the system than it would when cold.

If you are looking to extend the oil drain interval, then a fully synthetic is a better choice to minimise harm from premature oil failure. Standard mineral and semi synthetic oils offer satisfactory protection but be warned that they do not always last the service interval (depending on your style of driving).

What type of oil does the factory use?

This will vary between manufacturers and oil companies are keen to get this type of key account.  In some cases the choice of oil is based on tests, in other cases it is purely a commercial decision.  Check with the vehicle supplier what is recommended by the manufacturer.


In the case of your classic any oil you use now will be better than what the factory used in 1960.

Why does my oil go black just after I change it?

Firstly, engine oil is designed to hold very fine particles of material in suspension.  It has a dispersancy package that keeps the particles finely suspended and stops them clumping together to form larger. more abrasive and harmful particles.  These particles maybe fine wear debris from the component surfaces, or possibly Ďsootí, very fine carbon particles from the combustion chamber that get passed the piston rings through blow-by on the combustion stroke.  If you look closely at the oil, you can sometimes just about discern the very fine particulate in the oil.  In some cases the oil, when old, may actually feel gritty to the touch.

Diesels produce a lot of soot particulate compared to petrol engines and so as a rule, diesel engine oils have a higher level of dispersancy than petrol engine oils.  In more recent years, Exhaust Gas Recirculation has become normal on many diesel engines and so there is a tendency for more soot to appear in the oil, because as unburnt fuel is recirculated back into the inlet from the exhaust, some soot particulate is dragged through, too.   

The oil going black was always a sure sign that the oil had a good detergency and dispersancy package.  However, on newer engines with tighter clearances and more efficient combustion owing to the ECU, and partly thanks to modern oils, there is less of this effect occurring so it will stay clearer for longer.

My engine is modified, should I deal with it differently?

Your engine will be stressed a little more than the standard anticipated design usage and may generate more heat. For safety, extended reliability and reduced wear rate, superior oil should be used to counter the effects of the modification work.  Essentially, the higher film strength of a synthetic will reduce the impact of the increased loading from the extra modifications.

Film strength is the ability of the oil to support a load without metal-to-metal contact between the components.

Film strength at the bearing is dependent on the oil's capability to resist shear at the bearing.  Some of the best oils are expensive but do offer significant protection despite being a lower viscosity. This lower viscosity reduces friction from the oil at the bearing thus allowing more power to be transmitted to the drive-train. This kind of oil finds favour with motorsport people who are seeing very good engine life and oil life during a hard racing season.

Another reason to use a synthetic in a modified car is to allow for increase heat build-up when the car is used harder, as synthetics resist heat degradation better.

Should I keep this oil in until the next service schedule and just top it up for now?  In another words, can I mix oils?

Being pragmatic, I say better to have the right level of oil than worry about the mixing effects over time.   However, always try to stick with one brand as cross-mixing of oils can impair additive performance.  Generally, though, there will be no adverse effects from cross-mixing brands of oils.


Why is Idling bad for my engine?

Particularly on diesels, idling will not allow the full combustion to take place, so wet fuel remains in the cylinder and starts to run down the bores. This will reduce the wear control from the oil splashed up onto the cylinder walls, and further, will accumulate in the oil, lowering the viscosity and reduce additive effectiveness such as the dispersancy additive, causing larger particles to increase wear rates. In some cases the dilution can become dangerously high (>5%).

So, start your engine, and move off.  But remember; although the temperature may come up to normal quickly, the oil will take longer so let the car warm up properly (10 miles minimum) before exploring the revs.

Running in a new Engine

To minimise future oil consumption problems, it is advisable to take it easy during running or bedding in.  Some people suggest town driving is best, and to avoid constant revs in the same gear. If using the motorway, then drive at speeds between 55 and 70 mph, and also change gears a few times. However, don't be afraid to give the engine some short, sharp bursts of acceleration to assist the bedding in of the rings.  Opinions seem to differ on this, so check your handbook on a new vehicle or ask your engine rebuilder for their specific advice.

Avoid synthetic oils during running in, try for 10k miles before switching to full synthetic oils.  

However, the old school of running in an engine does not apply as much these days owing to the fact that the machining processes result in better finishes that do not need bedding in as much and as a result (and also, I suspect, to save money) manufacturers no longer offer a 1000 mile service, instead the engine is on a normal schedule of 12k-15k miles from the beginning.  In addition the assembly processes during the build of a new engine are much more automated and the cleanliness is far better resulting in new engines with far less potential for problems from day one.

From research I was involved with I know that wear can be radically reduced through finer filtration, and that automotive filters are not rated in the same way industrial filters are. From testing we did, we found an average 5BHP more on cleaner engines after 900hr endurance testing. Since wear will influence fuel economy and emissions, as well as oil consumption, it is better to stick with better quality oil, fuel and air filters, too.  So always ensure you use the best quality air, fuel and oil filters.


Switching to a Synthetic on new and used cars

DO NOT USE a fully synthetic until the engine has covered a little more mileage (approx 10k) because the engine is still bedding in for some time up to this point. Then switch to a good synthetic.

What are the benefits? Less wear, less power loss in the engine, better fuel consumption.

Generally, the reference to synthetic oil for an engine can mean a Group 3 Mineral oil.  But if it means a lubricant is formulated with a polyalphaolefin (PAO) base oil, then it is pure and is compatible with mineral base oils.

However, because the PAO base oil does not dissolve additives as well as a basic mineral oils, it is usually formulated with an ester co-base (usually di-ester and/or polyol ester). The additives are soluble with the ester and the ester is soluble with the PAO.

The PAO tends to cause seal shrinkage and the ester causes seal swelling, so the effects are offset when both base oils are present.

When switching to a fully synthetic on an older engine, or one with a higher mileage, it is the ester that can cause problems when one changes from mineral to synthetic. Ester base oil used alongside PAO base oil in lubricant formulation has excellent natural detergency. In other words, it will clean up deposits on component surfaces as a result of thermal and oxidative degradation of the lubricant. When one switches from typical mineral-based engine oils to a typical synthetic-based oil, the varnish layer will be removed by the ester in the synthetic oil and become suspended.

This suspended material can rapidly clog filters and can potentially block oil flow passageways and lead to component starvation. The same is true for gearboxes and other industrial machines. So think twice about switching to synthetic oils in applications where the engine or other machine has been operating for some time with mineral oils. It can be done but be aware of the potential for creating more harm than good.

This is also where oil seal leakage can be an issue as the beneficial layer of deposits on the seal are holding the oil in, but once cleaned off, the seal can initially shrink before settling again, so a short spell of oil leakage may result.  

On rebuilt engines of the older type, such as the MGB, the same applies, allow for bedding with a standard oil, and then switch to a synthetic, although there is some concern that the higher detergency will not allow a beneficial depositing on seals and as such, the oil consumption may prove a problem.  In my experience, with Mobil1 oil consumption has been no worse than with mineral oil and thatís using 0W40 in my 1980 MGB GT.  

How long can I store Oil?

Generally, if stored in a dry, moderately stable area with regard to temperature, then oil can last a long time.  However, additives can settle out after a period and so recommended best practice in industry is for a maximum shelf life of 12 months.  In a domestic situation, 2 -3 yrs would be acceptable assuming it has been sealed.  I would also suggest shaking the container prior to use to help re-suspend the additives that may have settled out.

I know that experts will say the oil can be stored for much longer, but allowing for the fact that the oil is often blended and packaged up to 2 years before you buy it, then the limit of 2yrs is a good safety margin.  Hopefully the oil will have been in good storage conditions in the retail stage between the blending plant and your car, but don't count on it either.

The same is true of grease, in fact the recommended storage is less, at 6 months in industry.  Again, for home use, 2-3yrs is ok, and possibly longer assuming your garage is dry and relatively protected from low temperatures.  However, a problem known as bleed happens with grease, and so it is advised to always store the grease gun and tubes of grease horizontally to avoid the oil bleeding off to the top of the gun or the tube. 

Any containers of grease should be kept sealed between use and if it doesn't have a loading/feeder plate on the surface of the grease then lay a sheet of plastic over the top to minimise the exposure of the grease to the air.

Brake fluids should not be stored for more than 2-3 years and only if unopened and the foil seal remains intact.  Any fluid already opened will have a shelf life of less than 6mths, possibly less if stored in the boot of your classic.



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