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MG MGF Technical - Why synthetic oil?

Is synthetic oil better then 'normal' oil?

I'm reading on this BBS several problems after changing the engine with synthetic oil. So I'm asking myself, why synthetic oil?

Allard
Allard de Graaf

Hello Allard,

I immediately swapped to fully synthetic oil after I bought my 97 VVC a year ago. I haven't had any problems whatsoever due to this swap. Advantage is because the oil is thinner it's should get the engine run smoother. It is also because you have a good feeling about it. Mind you the prescribed oil is a 10W40 semisynthetic oil, where as most fully synthetic oils are 5W50 (or something like that) where the 5 stands for low viscosity when the engine is still cold and has the advantage compared to 10W40 where the oil is thicker.

Cheers Marten
marten

Hi,

Allard, why synthetic? There are endless pages on this subject on the web, as you possibly know. There is also endless confusion and a number of lawsuits about the meaning of 'synthetic'. It's like democracy, everyone thinks it's a good thing but nobody quite knows what it means.

Both petroleum and synthetic oils are made of hydrocarbon molecules, originating from crude oil base stock. PAO synthetic oil (used in Mobil 1) is synthesised from ethylene gas using various chemical processes to produce a base oil. Synthetic esters and an additive package are blended into the base oil to give the final product which contains a small number of consistently sized hydrocarbon molecules.

Petroleum oil contains a far wider range of hydrocarbon molecules which are very difficult to eliminate during refining. The heavier molecules and waxes solidify at cold temperatures and prevent the oil flowing, and the lighter volatile molecules boil off at high temperatures causing the oil to break down.

Synthetics, with their controlled molecular structure, pour easily at very low temperatures, withstand very high temperatures, and don't break down so easily. I don't think that there is any doubt that a quality synthetic can be better in many ways than a quality petroleum oil, but cost and the development of petroleum oils make it far from an open and shut case. Indeed the gap between petroleum/semi-synthetics and full synthetics is small. This is helped by the confusing news that none of the popular synthetics, including Mobil 1, is 100% synthetic. That's synthetic as I would define it.

Mobil 1, like all oils, contains an additive package, supplied in suspension in a petroleum carrier oil. This carrier oil, which makes up around 20% of the product, is not classed as a lubricating oil. So technically Mobil 1 has never been 100% synthetic. However the Tri-Synthetic formulation introduced a further element. Mobil 1 Tri-Synthetic is made of PAO, synthetic ester and alkylated naphthalene, and - as far as I have been able to discover - alkylated naphthalene is a hydrocracked petroleum oil.

As for Castrol and Shell, both their 'synthetic' oils are hydrocracked petroleum oils. Hydrocracking is a process that eliminates waxes and other impurities from petroleum oils to produce a very high quality petroleum base stock, but at a lower price than producing a true synthetic. Court rulings in Europe have determined that synthetic is a marketing term and can apply to any processed oil, which must be a relief to Castrol, Shell, and now Mobil.

High quality synthetic and petroleum oils (which probably contain some synthetic components), are excellent oils, and I would have no worries about using either in my cars. It's just a little difficult for anyone who wants to use a 100% synthetic to be absolutely sure that they are getting it.

I run my '98 1.8 on Mobil 1 0W-40, partly because it's widely available. Some of the characteristics of Mobil 1 are overkill, as I doubt that I shall ever start my engine in temperatures of -40 deg C, or take the oil temperature up to 250 deg C (but some may do so!). I use synthetics as they flow better from what I call cold, they keep their properties far longer than petroleum oils, and they keep the engine internals squeaky clean. I have no problems using Mobil 1 in my MGF, but I did get an slight oil leak from the sump on my 214 soon after I converted to M1 many miles ago. As usual I ignored it.

Regards, Kes.
Kes

Thank you Kes, that was very informative :o)
Dot

go to google and search for the "engine oil bible" it might be a few links down but it is a very informative read, covering many other items including slick 50 and "topping up"

Will
Will Munns

If you change the oil to synthetic, don't forget to check more often your oil level. Indeed, a lot of engines drink more synthetic than regular oil.
Arnaud

have a read at this site :

http://www.cpinternet.com/~ennyman/a-pages.html

may require cut & paste.

regards
Jason

Hi,

Cheers, Jason. It's a pity that Amsoil is not sold in the UK, or isn't easily found if there is a UK agent. Years ago a friend of mine was a home dealer, but he soon dropped it as nobody bought anything off him - me included.

Regards, Kes.
Kes

This thread was discussed between 26/05/2002 and 04/06/2002

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