REPAIRS PAGE 26
ENGINE OIL-SPOILT FOR CHOICE?
No one can have failed to notice the recent explosion in the
range of engine oils on the market -- it has certainly caused me some confusion.
For the past 25 years or so life has been relatively simple for respect - ie
using a good premium grade oil (such as GTX ) – and changing it every 4-5,000
miles. This has served me well without any trouble over 500,000 miles in my
various family cars. I would have little doubt that I could continue to do so
under the same circumstances and would have no qualms about it.
However there is no escape from the fact that these newer synthetic oils are
superior in many ways - and effective - if used in the right applications and
circumstances.
In brief these synthetic oils are produced by a series of chemical processes,
which are more complex and precise than the best refinery produced mineral oils.
This gives advantages in many areas, notably film strength, thermal stability,
and service life etc.
Inevitably these synthetics cost more, so are they a viable option? Well, to
me it literally depends on the way you use your MR2.
I have talked to various oil majors and independent consultants, and this is
my summary of these discussions, ie their opinions -
a) The 4-AGE engine is considered in the ‘advanced’ category by the oil
industry as despite its relatively old age it was well ahead of its time in
design.
b) Engine oils to use - well it depends on your inclinations-
If you are a ‘traditionalist’ you can’t go far wrong with a good as GTX or
equivalent - as long as you change it often, around 4-5,000 miles.
If you hammer your car down motorways continuously then a fully synthetic oil
1OW-40 or 15W-50 is suggested. OW-40 oils are OK but they can leak when cold -
(these are actually designed for the tightest of modern engines - and not
actually for engine longevity but rather for fuel economy ‘figures’.)
For low mileage short journey motoring then a semi-synthetic is suggested.
The particular advantage of one of these oils such as Magnatec, is that it has a
polarising action to give very powerful boundary film lubrication to moving
metal surfaces. The very action of the moving engine parts actually repolarises
the oil molecules to stick to the metal and provide enhanced lubrication. This
is apparently regenerated each time the car is started from cold - hence the
applicability to occasional starts and/or short journeys.
The polarisation does eventually fade if the car is left for long periods -
so don’t expect it to work immediately after weeks of standing!
That’s the theory anyway!
I don’t wish to favour any particular oil major - but I am tempted to try
moving up to semi-synthetic oil.
As always there is subjective judgement and personal preference to add to the
decision process, and I could easily see myself using any of the above oils
depending on my, driving circumstances.
So - you pays your money and makes your choice!
ALAN JONES
SYNTHETIC ENGINE OILS - BLESSING OR CURSE?
In the old days when I was a lad (yes alright then - the very old days!) the
choosing of engine oil was so much simpler - synthetic oils were still well into
the future. Castrol and Duckhams dominated the road market - with mineral oils
such as GTX 20w-50.
But for us road users then - even using relatively high powered engines (for
the time) - such as Lotus twin cams and tuned Cooper S's - those mineral oils
did pretty well. In fact I can't recall any failure that could be put down to
those oils, which are now regarded as 'old-fashioned.'
Younger members might assume that those old engines never delivered the power
that a MK1 can - but on recollection that is actually not entirely true. A true
comparison has to be made on 'specific power' ie bhp/litre. - for example a
moderately tuned Lotus twin cam exceeds the MR2 N/A on this measure. Being a
Lotus perhaps not for long - usually bits and electrics falling off -Lotus was
renowned (a little unfairly) for being "Loads Of Trouble - Usually Serious".
This was more due however to the electrics (fibreglass bodies need return wiring
- a nightmare for unreliability.) The engines however were excellent –and
certainly had no problems with mineral oil.
Even the original (when well-tuned) 1275 Cooper S's equalled the N/A specific
output.
Some might reasonably say 'so what - isn't that just history – what’s the
point of this story?'
Well - these engines were perhaps somewhat basic compared to modern CAD
designs - but they used some very high quality components to compensate. For
example I would give my back teeth to fit Nimonic-sodium filled exhaust valves
and copper-lead main bearings to my S/C - yet they were standard on my old
Cooper 1275S. So were many other material features that the MR2 just cannot
match.
These features tended to carry a price - poor surface lubrication properties
which demanded a good lubricant. Yet GTX never failed in this respect.
So - I contend that is a bit of a myth that 'oldie' mineral oils are 'old
hat' and were only any good because all old engines were less stressed - some
were as stressed as modern engines.
Before I get too nostalgic for these classic oils I would have to say that
they need to be changed regularly - 6,000 miles maximum.
I would also say quite unequivocally that an oil such as GTX is perfectly
good for an MR2 N/A - with the proviso that it isn't thrashed to hell and it is
changed every 4,000 miles/yearly.
Going one step up is Magnatec - which is semi-synthetic and proclaims
polarisation as its virtue. It claims to 'stick to metal' to give good start-up
lubrication - I have talked to Castrol and have no reason to disbelieve them -
but I haven't tested it myself.
Moving on to synthetics - now the minefield!
What is no doubt that these oils have-
a) Superior boundary lubrication properties than the above-mentioned mineral
oils.
b) Far better resistance to oxidation.
c) Much better intrinsic multi-grade properties.
Sounds too good to be true doesn't it - but read on -
The downsides are-
a) Price - a tad expensive at around £30 for 5 litres.
b) A bewilderment of viscosity ratings - from 0w-30 to 20w-60 - enough to
confuse anybody - including me! Talking purely personally I would not use any of
the above - the former to me is just too light for the big ends - but good for
the camshafts. The latter is OK for the big ends - but too heavy for getting
quickly to the cams.
c) Not surpisingly therefore - I use a middling 10w-40 viscosity - Amsoil -
not cheap - but the best spec.
Now to some feedback downsides on synthetics-
A club member mentioned to me at Billing the sad tale of their car’s big-end
failure - after only 200 miles on synthetic oil.
This frankly should not happen - and has caused me some very deep thinking -
and this is the real reason for this article.
One theory put forward is that synthetic oils carry heavier levels of
detergents than the old mineral oils. This is contended to create a 'fall of
soot' in the bearings - thus blocking them, causing then to fail. I have checked
this out with Castrol - the detergent levels are less than with the old oils -
as they are more resistant to oxidation.
Use of flushing oil - if anyone younger than me knows what that is! It is a
highly detergent low-viscosity oil that is just about unobtainable unless you
have trade contacts. I really can't recommend this - it can only be run for 5-10
minutes and the 'soot fall' on an old engine could be severe.
I have personally not had the slightest problem in changing from mineral to
synthetic - and many other members have done so equally successfully.
Nevertheless - it does concern me that a such a member has had so unfortunate
an experience - so it begs the question - is this a random event - or pure bad
luck - or anything to do with synthetic oil??
Has anyone else got experience or comments - please forward them to me!
ALAN JONES
OIL CHANGE HELP
I went to another of the weekly Wednesday night pub meets in our Midlands area
(where were you?) last night, and one of the subjects talked about was starting
your car up for the first time after a long break or changing the oil. There is
a big chance that the bearings will be very dry through the oil draining
completely away into the sump. The filter should have a non-return valve fitted
but other pipes and oil ways will drain after a period of time. The safest way
to stop any engine damage is simply to detach one end of the thick wire from the
coil to the distributor so the engine will not fire when turned over. If you
turn the engine this way for about 5/10 seconds you should see the oil pressure
needle on the dash go up to quite a high reading, thus lubricating all the
bearings without putting any pressure on them. When you connect the wire back up
and start the engine it will have oil pressure immediately so no damage should
be caused. Another thing to do when fitting a new filter is to fill the filter
full before screwing onto the engine, thus saving 2/3 secs of engine wear as it
does not need to be pumped full when first started up. When I first bought my
MK1 I knew I would keep it for a long time. It has now done 123,000 miles, about
80,000 are mine. I have always done an oil
and filter change every 4000 miles using the above advice and the best modern
oil. My engine hardly uses any oil between changes, has no knocking or rattles
and holds a good 30/40 p.s.i when hot at tick over (800 rpm) rising to 70/75 psi
at speed. All simple advice but very important.
Have fun
Isabel from Loughborough