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Engine oil is boring, right?
We change it (or get someone else to change it) once per year then when it's in the car we forget all about it.
Oil is, however, an extremely important part of a well maintained engine and has a huge role to play in the lifetime of a car.
Engine oil is of course responsible for lubricating the engine; preventing metal from touching metal and causing wear. The oil in the engine has far more to do than just lubrication, however.
The oil in the engine must:
i) Perform its essential lubrication, preventing wear.
ii) Remove small metal particles (swarf) from the moving parts and carry it safely away.
iii) Mop up acidic combustion bi-products.
iv) Carry away heat from the engine.
v) Clean the engine.
vi) Minimises corrosion by preventing oxygen getting to the metal parts.
The oil must perform all of the above in a wide range of conditions. It must be thin enough to work from cold on a freezing cold day at -10C, yet thick enough when operating at the extreme pressures and temperatures of a fully warmed up, hard working, engine. All of this from a single fluid!
We demand that the oil we fill the car with once a year does all this and continues to protect the engine for up to 12,000 miles. In 12,000 miles a (rough) calculation shows that the engine will have gone about through over 5 million revolutions in that time!
So engine oil is an amazing product but, however, as you may have realised, not all oils are created equally. There are two types of oil for car engines, mineral and synthetic (actually there are three, with semi-synthetic being a mixture of the two).
Mineral oils are prepared from a crude oil base and are the cheapest engine oils to buy.
Synthetic oils are specifically formulated to have the specific properties required of an engine oil. Being synthetic, they're naturally significantly more expensive than mineral oils.
Cheap mineral oils will do the jobs detailed above: for a time. In the conditions of a car engine, they do not keep their properties for more than a few thousand miles. After this, the corrosion products are no longer mopped up, and they can break down causing the dreaded 'black sludge' that can lead to seizing up of the engine.
A good synthetic oil, on the other hand, can easily perform its duty for a full 12,000 miles. During this time it will fully protect the car's engine as described above.
Mobil 1 is a high quality synthetic oil designed for highly demanding conditions. Ironically, use of a car for short trips, with many cold starts can be extremely stressful on the engine and oil.
I use Mobil 1 0W 40 grade. It is not cheap, Halfords have 5 litres for a wincingly high £47.99 (but, you can get it cheaper; I'll reveal where from later). The 0W indicates that it has a low viscosity for cold starts, the 40 indicates that it has a good viscosity when the engine is up to temperature. This gives the best of both worlds; the engine is quickly protected from cold and the thin oil causes less friction so gives better fuel economy.
If you're buying oil for your car, check the owners manual and ensure that the oil you purchase has the same specification or better (i.e. 0W 40 is 'better' than 5W 30 as it has a lower viscosity at low temperatures and is better at high temperatures, so would do the job).
Mobil 1 is supplied in an easy pour container. The extendable spout makes it easy to pour out, and the oil flows easily into the engine. Five litres is more than enough for my car (and should be for most), leaving some left over in case the car needs a top up during the year.
I've now used this oil for three years. I change the oil myself, so am in a position to see the condition of the oil upon removal from the car. Previously, using mineral oil, the oil came out of the car looking thick and black. With Mobil 1, this change in appearance and consistency does not happen; a darkening to a golden brown is all that's apparent, with the oil appearing as free-flowing as when it was put in a year ago.
Clearly, the Mobil 1 has retained its engine protecting properties throughout the entire time of its use, whereas the mineral oil had 'given up the ghost'. Since using Mobil 1 (in two different cars), I've not noticed any sludging up of the engine whereas this used to happen with mineral oil.
Since using Mobil 1 in my latest car (replacing what looked like cheap and nasty oil), I noticed a very slight improvement in fuel economy as well as what seemed like a quieter engine (this makes sense as a thinner oil could lubricate parts that an oil well past it's best could not).
In summary, if you don't care about the condition of your engine, or you change your oil every 6000 miles then buying Mobil 1 may be overkill. On the other hand, if you drive hard (or subject the car to frequent cold starts), or want to keep your car for a long time, consider a fully synthetic oil like Mobil 1.
Having said that Mobil 1 is expensive, it is available much cheaper than at Halfords. Costco have it on sale for around £23. Compare this with £15.99 for Halfords 'enhanced' Mineral oil and I think the choice is clear. Highly recommended.
Finally, a tip. If you get your car serviced by a dealer, and want to use your own, selected brand of oil, tell the dealer you'll be bringing your own oil with you (giving him a chance to say no, and you a chance to go somewhere else!). In this way, you avoid the extortionate price dealers can charge, and you'll know what type of oil is going in the car.