Author Topic: Synthetic engine oil  (Read 7433 times)

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amam

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Re: Synthetic engine oil
« Reply #30 on: May 15, 2012, 10:46:43 PM »
im a mechanic, i just get to know what is good oil and what is recycled, its not that bad but will just burn, degrade and blacken quicker than normal oil, the thing that annoys me with it is i now buy unipart 20/50 for £15 for 5 liters and comma classic 20/50 is about £18 now but there blue bottled comma motorway 20/50 is £12 and pretty much same recycled green oil, except one had a posh tin with graphics of a mini on it  :P

bis13

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Re: Synthetic engine oil
« Reply #31 on: May 15, 2012, 10:54:26 PM »
i am gutted i had you for a science boffin in a millets kagoul!! turns out your a spanner monkey!! i am brainwashed by the magic adverts in classic car magazines and thus cannot turn away from the dark side, also may i add i love a good chinese takeaway and love old re runs of monkey so i cant knock the hoards of communist chinese that will one day rule us all.... also "synth oil" sounds to much like an old kraftwerk album...

mile

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Re: Synthetic engine oil
« Reply #32 on: May 16, 2012, 06:41:44 PM »
I know in VW land they have a special 'aircooled' oil called beetle juice which is thinner than usual. With A/C engines relying on the oil for cooling, thick oil doesnt tend to do them much good as they cant circulate as freely to cool down. I know the 126 has its cylinders going up and down rather than a slightly tilted boxer as in a VW but it seems to make sense to avoid thick oils.  Personally i think if you have an oil leak you should be sorting it rather than trying to block it with a thicker oil!

..functions other than lubricating oil is cooled engine. too thick oil circulates more slowly and leads to overheating of the engine. semi-synthetic and synthetic oils are thinner but stronger oil film, much more resistant to overheating ....

Today ... there are much better seals (gray)

RicePuddin

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Re: Synthetic engine oil
« Reply #33 on: July 16, 2012, 01:49:37 PM »
I've just read this thread and I am more confused. I'm just going to get a 20W50 brand name like Mobil. If there is no leaks then that's the one for me. I'm going to also try the NGK Iridium plugs too.
I'm delighted that I bought an oil vacuum pump. It removes the engine oil through the dipstick. It will also work on the gearbox too.

Xylaquin

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Re: Synthetic engine oil
« Reply #34 on: July 21, 2017, 12:35:35 PM »
Having assembled a near enough new engine, I was researching breaking-in oils and assembly lubricants to use and came across these threads on general oil usage.

Viscosity

According to the 3 different aircooled owners manuals, your oil should be based on temperature.
  • If the temperature is no less than -15 and no higher than 35, then it says to use 10w30
  • If the temperature  is no less than 0 and goes above 35, then it says to use 20w40
  • The Personal 4 manual says to use 15w40.
Given the UK climate, unless you never use you car when it's near freezing outside, I'd question is it wise to use anything higher than 15w40 in an aircooled?

According to the BIS owner manual it says we should use 15w40.
In fact it even says we can use semi synthetic or mineral 15w40, which leads me to my next topic.

Synthetic vs Mineral
The aircooleds were designed with mineral oil in mind, the BIS can take either.

There seems to be a misconception about synthetic oils being thinner, but that's not the whole picture. A 10w40 mineral oil has the same thickness as a 10w40 synthetic oil, if by thickness we're talking viscosity. The difference is, synthetic oils can withstand more pressure before breaking down. For example, when a tappet is pressed up against the camshaft, both oils provide the same thickness between the surfaces. But hypothetically, if that tappet were pressed harder and harder against the camshaft, the mineral oil would break first. Now because many newer engines have greater pressure against various surfaces inside them, they use synthetic oils, thus synthetic gets the reputation of being thinner.

I guess the main point of debate in synthetic vs mineral is the leak factor. There are hundreds of internet forum pages and articles arguing about the legitimacy of this. When researching, I reasoned that if the true answer were obvious or easily proven then we wouldn't even see hundreds of debates on this. Ultimately I seems to comes down to the condition of your engine, more specifically the condition of your oil seals. The older more worn they are, the more likely they are to leak if you use synthetic.

126 oil seals are easy to come by and cheap, what aren't easy to come by (for BIS owners at least) nor cheap, are camshafts and other chunks of the engine... leading to my final section: zddp.

Zinc dithiophosphate
ZDDP for short, is an anti-wear oil additive that contains roughly equal amounts of zinc and phosphorus and is particularly critical for the correct lubrication of flat-tappet camshafts. The amount of ZDDP has decreased over time with the broad adoption of roller-tappet cams and the negative impact ZDDP has on catalytic converters and the environment.

Most oils have an API approval, with the letter after the S signifying the classification.
  • In 1980, the oil standard API SF specified a minimum of 1200 PPM and maximum of 1500 PPM
  • API SG reduced the minimum to 1000 PPM and the maximum to 1200 PPM
  • API SJ reduced the maximum to 1000 PPM, I can't seem to find a minimum being specified
  • By 2004, API SM was introduced and the minimum lowered to 600 PPM, and a maximum of 800 PPM

This isn't a problem for engines as time has gone by, because newer and newer engines become more efficient and better designed against wear. But for old engine with basic flat tappet arrangements, a design that is more prone to wear than a roller tappet, it is a looming problem.

The BIS owner manual specifies API SG (SF if you use mineral), which corresponds to the oil standard at the time of it's introduction. The Aircooled owner manuals all specify API SE, which was the standard introduced in 1972.

When I was looking up ZDDP, it seems that not longer after API SM was introduced, a wave of flat-tappet camshaft failures were sprouting up. It occurred more in engines where the spring pressure was greater but consensus on forums I've been looking at suggests that once we go below 1000 PPM, cam failures start cropping up. This puts the last "safe" API as SJ... but even then there's no lower limit!

For BIS owners, this may even be a non-issue since the camshaft and tappets are immersed in oil, so long as the oil level is kept topped up:



However for aircooled owners, where the camshaft is above the oil and the engine was designed back when API was down at SE, perhaps it's worth adding some zddp additive, or looking for a classic oil that is SE/SF grade.

Big long article about zddp levels and history of oil etc.
« Last Edit: February 23, 2018, 01:31:14 PM by Xylaquin »

Gadge

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Re: Synthetic engine oil
« Reply #35 on: July 21, 2017, 02:25:58 PM »
HOLY THREAD REVIVAL BATMAN :P i've read this thread a few times now and it's very interesting what views people have. I'm no oil expert but I do agree with someone's comment on regular oil changes are the key to a reliable engine. I've been using castrol gtx now for a number of years (15w/40) and it gets done every year regardless of mileage as I believe you can never do too many oil changes on your car.

I'm not sure if castrol gtx is synthetic or not (I suspect it is) but I've just come to the end of a 5 litre can of it and have took the plunge and bought 5 litres of shell helix as it was cheap (it was bought in error apparently)

I will say though imo if an engine is leaking oil then I'm not sure it's the oil spec that's doing it  :$
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Xylaquin

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Re: Synthetic engine oil
« Reply #36 on: July 21, 2017, 05:12:23 PM »
I've been using Castrol GTX 15w40 too, which is part-synthetic. In theory it's the perfect oil for an ol' BIS engine as it's designed to clear and protect against sludge (at least, as much as is possible with just oil!) But it's API SL, so at best it has 1000 PPM, but it could have less. Again, in a BIS engine this may be a non-issue.

I figured changing my oil every 3 months would be good shout.
« Last Edit: August 01, 2017, 01:10:21 PM by Xylaquin »

Xylaquin

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Re: Synthetic engine oil
« Reply #37 on: August 01, 2017, 01:15:36 PM »
found a product: Mannol Universal.

It's a 15W40 mineral oil with API SG, perfect specification/zddp for 126 engines. Plenty of sellers on eBay, but can be bought from the manufacturer on Amazon for £15 for 5L  :)

Amateb8

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Re: Synthetic engine oil
« Reply #38 on: September 19, 2019, 12:54:49 PM »
I thought I'd put away invoices for my Fiat 126. I noticed Proeitti used 10w40 semi-synthetic oil. I previously used Mobil Super 1000 15w40 semi-synthetic oil. The consensus on this thread is 15w40. I was thinking of making an oil change in about 6 months time, and replace it with what I previously used - 15w40. Is a 10w40 thinner. Should I do an oil change sooner?

Gadge

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Re: Synthetic engine oil
« Reply #39 on: September 19, 2019, 07:54:16 PM »
10w40 is a thinner oil on start up meaning it flows slightly quicker than the correct 15w40 oil. A faster flowing oil doesn't necessarily mean that it's good for the engine. Thinner oil in an engine designed to run on thicker oil means a lower oil pressure and noisier components like the tappets. 10w is only slightly thinner so it's unlikely to cause any damage to a BIS engine and will lubricate all the bits perfectly well enough but personally for the price of a good quality 15w40 oil - less than £20 for 5 litres - you might as well stick to spec and do an oil change and feel good about yourself while doing it  :D incidentally in my personal opinion I use mineral oil as my preference.
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