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Knowing that it's too expensive to guess about these things, could any of our techies give me any guidelines for using synthetics. And finally, (I hope this doesn't sound too dumb) are there different types of synthetic motor oils? I sometimes see references to semi-synthetic oils and am confused. I really appreciate any clarification you can give this mechanical illiterate - Thanks much.
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I haven't any techie details. However, I have an oil temperature gauge in my car. For the first 20000 miles I used castrol magnatec (advanced, semisyn), then last month I changed to the fully synthetic castrol RS. I have noticed that at a steady 80-90mph on the motorway the oil is running at 20 degrees less with the fully synthetic oil. I wasn't expecting results like that when I decided to make the change, I just expected, perhaps, better fuel economy, or better performance. However maybe the results are due to different heat performance of the different products, maybe the temperature difference is not completely due to a reduction in friction. Anybody got the answer?
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To my simple mind a 20-degree drop seems a hell of a lot - from 100 to 80, or what? There must have been a huge amount of friction previously, unless the timing has been affected? I thought the coolant cooled the engine, not the oil?
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As i said I've not changed my engine husbandry at all apart from the type of oil. The heat produced by the engine is a combination of factors, obviously the energy released by combustion but also friction between the moving parts. If the oil is more effective then not only the engine but also the oil runs cooler. I do mainly motorway miles and I stick at a steady 90mph in the right conditions, the oil used to run at an indicated 120 deg but now stays level at 100deg. When I was in france recently I really pushed it and I had to run a steady 105mph to push the temp up to 120deg. I also notice that the oil pressure is much lower at idle than it used to be with the old magnatec.
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If the pressure has dropped (and the bearings are not disintegrating), and the oil temperature has dropped, then surely the only answer is the viscosity of the oil is lower. Or to be more precise, the shape of the viscosity vs temp curve must be different. I assume that the basic oil specn that you have used remains the same?
There must be an oil industry expert out there somewhere, I am sure that we will accept anonymous contributions.
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the magnatec is 10-40w asopposed to 0-40w for the RS, otherwise i haven't a clue!
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I've just been to France and bought Magnatec which is 5W40 fully synthetic, while British Magnatec seems to be 10W40 semi-synthetic. The price was, of course, much lower in France.
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Jimmy
A great deal has been posted in HJ on this subject I recommend you try a search Also try the site below for a detailed tech background written for the everyday person..
www.chris-longhurst.com/carbibles/index.html?menu....l
Regards,
Julian
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Next time you go to France buy Synthetic oil to fill the spaces between the beer and wine bottles - it's about half price there and was also the subject of a letter in the HJ section of Saturday Telegraph some time ago.
Some years ago I studied lubricants / materials for gears of the fleet. Only a very small amount of oil is needed for lubrication but if it overheats the oil film breaks down and you get catastrophic scuffing failure. It is a prime factor of engine oil that it is used to dissipate heat.
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The recommendation to buy oil in France is a good one. I always bring back two stroke oil for my son's Yamaha RXS 100. Last time we went, semi-synthetic 2T was about one third of the UK price.
BigAl
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