Cheap oil

[john.r.davies]

See: http://lucasoil.com/images/documents/Zinc_Values_MotorcycleOil.pdf bottom right

J

[Peter Cobbold]

Peter, hi, so what's the magic zddp content then. I'm using Comma 20/50 mineral oil in mine on the assumption its OK ?

Robin,

I was hoping no-one would ask. Michell's book gives chapter and verse, and doesn't stipulate a value either. But he shows its complicated.

My precis:

There are lots of different ZDDP chemicals with different heat sensitivities, and P/Zn ratios.

Dont use diesel oils in si engines as the type of ZDDP in diesel oil needs much hotter conditions to work. ( By inference an oil cooler on a road car 'cruiser' might not allow ZDDP to work). Trick camshafts might not be protected by ZDDP. Running in a new cam needs correct temperatures to be reached to activate ZDDP. The sulphur in it reacts with copper, so too much can affetct bearing shells.

Avoid European ACEA-category oils that are catalyst compatible with: C1. C2....etc

Choose oils that are A1 A2 etc or B1 B2 etc.

 

Read the book, its an eye-opener.

http://www.amazon.co.uk/Which-Oil-Choosing-collector-Paperback/dp/B00GSD7QSW/ref=sr_1_2?s=books&ie=UTF8&qid=1412277135&sr=1-2&keywords=%22which+oil%22

 

I look for around 1000ppm P.** (ie Roughly 0.1%) but I drive the torque, dont run a trick cam, and shall ditch the oil cooler.

 

Peter

 

** Michell p17 cites historical levels.

Edited October 2, 2014 by Peter Cobbold

[Eddie Cairns]

 

Of course not, Eddy! D'ye think that Asda will tell Joe H. Public where it gets its ultra cheap engine oil?

But I did't mention Asda, you did.

 

 

John

 

You said

 

"Cheap supermarket oils are used oil, filtered and re-refined."

 

This is a cheap supermarket oil. Are you backtracking now.

 

 

 

 

 

[ctc77965o]

I still advocate the Diesel 20W50

The petrol engine oils of API SM or newer have low additive levels to support lifetime of catalysts. Old design engines need the higher additive levels due to their design (the whole ZDDP story), diesels have no catalysts and more extreme lubrication requirements - so these oils have more of the additives old petrol engines need. These oils are not recommended for modern petrol engines because of the catalyst problem...but for old engine designs it's a different story.

Diesel engine oils also have high detergent content - and there is a risk your old engine gets 'too clean'...

 

and it's cheap.

[Shuthonger]

After an engine rebuild I changed my running in oil (Halfords classic 20/50) to Mobil one at significant cost - about £10 a litre from Halfords. But without a doubt the engine is quieter, smoother and I am sure it feels more powerful.

 

I'm covinced anyway so for extra few quid each year, that's what it will getting from now on. Mobil one claim that the engine should not experience any significant wear once installed.

 

I don't know about that, but I swear I can feel the difference.

[Peter Cobbold]

I still advocate the Diesel 20W50

The petrol engine oils of API SM or newer have low additive levels to support lifetime of catalysts. Old design engines need the higher additive levels due to their design (the whole ZDDP story), diesels have no catalysts and more extreme lubrication requirements - so these oils have more of the additives old petrol engines need. These oils are not recommended for modern petrol engines because of the catalyst problem...but for old engine designs it's a different story.

Diesel engine oils also have high detergent content - and there is a risk your old engine gets 'too clean'...

 

and it's cheap

And its also wrong to use diesel oil in a si engine, whatever its age.

Read Michell's book - he's an professional oil expert. He is quite clear that diesel-type of ZDDP doesnt work in petrol engines.

[ctc77965o]

Peter,

 

I won't use Bold, but I think you're wrong, ZDDP function is more to do with radical scavenging than it is with the decomposition to dialkyldithiophopsphoryldisulphide - temperature is not the initiator, its the hydroperoxide concentration. Yes there are different aryl functionalities, but the lubrication performance of ZDDPs does not correlate with their thermal stability.

 

Diesel engine oils have a superior anti-wear formulation for old petrol engines.

[Crawfie]

Can someone translate please :-)

[jemgee]

I've raised the query with Asda customer services as to spec and additives and detergents etc. The guy I spoke to was very helpful and contacted their buyer who will contact the manufacturer to get the info. I will post when I get an answer.

[RobH]

"Diesel engine oils have a superior anti-wear formulation for old petrol engines".

 

Unfortunately that statement is directly contradictory to the advice on page 117 of Michell's book where he says categorically " ...do not use heavy-duty diesel engine oils in passenger cars....". and he quotes an instance of a truck oil with high values of zinc and phosphorus but which failed the standard wear tests for petrol engines. By heavy-duty he means specifically formulated for truck engines.

 

I am not going to quote further as those interested should buy the book and make up their own minds, but his reasons would appear to be plausible to the layman. He does say, however, that oils with A3/B3 ratings (SL/CF in the US) intended for light - duty car or van diesel engines should be acceptable in general.

 

At the end of the day its up to each owner of course but for the sake of the cost of a round at the pub, is the doubt worth the saving ?

 

Rob

[Peter Cobbold]

Peter,

 

I won't use Bold, but I think you're wrong, ZDDP function is more to do with radical scavenging than it is with the decomposition to dialkyldithiophopsphoryldisulphide - temperature is not the initiator, its the hydroperoxide concentration. Yes there are different aryl functionalities, but the lubrication performance of ZDDPs does not correlate with their thermal stability.

 

Diesel engine oils have a superior anti-wear formulation for old petrol engines.

Dave,

Apologies for shouting.

Antioxidant properties you raise were discovered in the '30s before the boundary lubricant benefits of ZDDPs was recognised. They are distinct functions in the oil.

Antoxidant action reduces gumming and lacqeur formation, particularly on bearings.

The lubricant effect requires the ZDDP to decompose and cross-link to form a complex, glassy, phosphate-rich coating on the surface of the cam follower ( tappet). This process requires a high enough temperature and mechanical pressure.

A GoogleScholar search for ZDDP+tribofilm shows where we are. Heres one paper that's not behind a cursed paywall:

http://eprints.qut.edu.au/6175/1/Pressureinducedcoordination-paper.0905.pdf?origin=publication_detail

We can see that the chemistry of Zn-Fe-Phosphate film formation is complex and still not fully understood. So oil companies formulate oils by wear measurements on running, loaded engines, both diesel and petrol. The specific ZDDP species will be different since conditions of pressure and temperature are different.

Michell is quite clear in his book ( p117). He gives an example where a high-ZDDP diesel oil, with well over 0.08% Zn or P, failed a petrol engine test that involves measuring wear in sliding or flat tappets. Meanwhile petrol oils had to pass at 0.08%P.

Thats why I stick to petrol engine oils with ca 1000ppm P.

Peter

Edited October 3, 2014 by Peter Cobbold