MGB Register Forum

Steve

For a further explanation on oils see Paul Hunts site
http://www.mgb-stuff.org.uk/enginetext.htm#oils

Michael

Read it - it's an excellent website.
Thanks

Hi Guys
Try Classic oils at Bicester Heritage. They sell all the major brands at keen prices and their web sit list the full spec for all the oils they sell including the ZDDP content. They make their own blend of 20/50 for 20 pounds with a ZDDP 1300. They also sell Duckhams for 30 pounds.
Ps I have no connection with Classic oil , just use them because they are local to me.
Best regard
Mike

The classic oils website is very illuminating. The Morris golden film I'm using has 700 ppm ZDDP, Castrol Classic 800 ppm ZDDP, but Duckhams 1300 ppm (parts per million). The Morris is said to be their best selling 20W/50 might have something to do with it being the cheapest. You get what you pay for I suppose. Makes you think how much ZDDP is required, is more better? Morris say there oil is low dispersant, which for engines like the B series with a proper filtration system doesn't seem to be a good thing. I'll keep putting the STP in I think. I can see me going back to good old Duckhams Q20/50.

Just to complicate things further have a look at the penrite classic light 20/60W

Surprisingly some of the oils are quoting obsolete API standards, maybe the standard has been superceeded by later designs of oils yet some manufacturers are stll manufacturing to the old standard for classic cars.

Paul, i always used STP in the old days, but not used it in my cuurent classic MGB, will have a look at its today specs.

Just remembered Martin Williamson, on MGOC site, gave an explanation of oils. Sorry its a bit long winded.


Right, clearances, that is the issue of the viscosity and if a synthetic and a mineral have the same viscosity grade then that argument is out the window. Whilst the molecular structures of mineral oil may vary whereas synthetic oil molecule structures are more consistent, the machining tolerances play no part except in terms of the viscosity and potential then for leakage problems occur only if one uses a modern 10W-30 in a worn engine or one not precision machined instead of a more standard 10W-40 mineral oil. The basic premise as defined by the Stribeck curves is that the factors that affect the ability to achieve thick films in the sliding contact zones are load, speed and viscosity for a given clearance.

There are a number of other arguments that suggest a synthetic is not ideal for an older engine, the only one of which I would say holds any water is the issue of elastomer compatability or in the case of the pre-war designs the lack of sealing that matches the post-war seals.

The biggest counter to synthetic is the actual cost and if the engine is burning it heavily through leakage and wear than there is little point putting the expensive stuff in. That said, synthetics actually produce lower levels of deposits though in the combustion area and are used in industry in high temperature applications. Probably one of the biggest gains in engine cleanliness and oil life is not so much the precision machining but the finite control that is now brought to the fuelling and the ignition. Plus the fact that rebuilt engines can benefit from both better machining and added solid state circuitry. I know, I ran an MGB GT with a modified B Series with mappable ignition on Mobil1 (0W40) for over 30k miles, much of that in the outside lane on motorways, and though regular oil tests I found the oil was still in good order for in excess of 15k miles.

Secondly there is an optimum level of ZDDP in an engine oil and too much can start to cause problems with the intergranular stuctures of the material. The optimum amount is around 1000ppm of phosphorus, and any more than 2000ppm can start leading to spalling of the surfaces.

The fact is that the current levels are around 800ppm, marginally below the optimum levels of around 1000ppm and have added Boron for assistance. In fact the levels currently are very similar to those of the 1950s/1960s. The reason it was increased in the 1970s - 1990s was that the oils, in order to last longer, needed higher levels of anti-oxidants and guess what, the anti-oxidant also has Phosphorous, and so ZDDP was increased to aid the oil life. The wear associated on cam followers and the cam lobes is usually a failure of the oil's viscosity to maintain the film strength rather than any lack of ZDDP. Mineral oils have poor shear stability in comparison to modern synthetic oils so as a consequence, in the desired thick film hydrodynamic lubrication regime at the cam and follower interface, the mineral oil is susceptible to shearing and resulting in boundary contact in the worst case scenario, or mixed film at best. A synthetic is Newtonian and thus resist thinning under that shearing load.

A quality oil will be submitted for testing by API to attain an API classification as either a Service (Sx) or a Commercial (Cx) oil. Our petrol engines require an S rated oil, diesel a C rated. The testing sequences for Service rated oils include for valve train wear on both bucket lifters/sliding finger type followers without a roller, as well as flat bucket type as on the B Series. More importantly, API requires oils to have backwards compatability for older engines, hence the reason they still run the valve train tests.

So, being qualified in lubrication, and having researched the subject quite extensively over the last 30 years, I don't buy this myth that ZDDP at these elevated levels is required.

What I will say is that unlike 10 years ago when people were more likely to be using older cars than they are now, 99% (ok, that's a guess) of classic car owners are likely to do less than 3,000 miles per year or less, and in the case of the MGB (or Midget, et al with the A/B/C Series engines) then most oils will suffice as it is unlikely that given the annual mileages, most of us will either sell the car on or the car will out live us.

More to the point, when people recommend an oil, there's often, if ever, any scientific evidence to suggest that one is better than another and even then the quantifiable difference is probably meaningless in the grand scheme of things, and what is top dog in the business will eventually lose its crown to something else. Sure, avoid really cheap, non-API S Rated oils but life is too short to worry about what product is best. Just let's not start on the "it must be 20W-50" argument.

Duckhams Q20-50 and Castrol 20-50 is recommended although the former costs just short of £35.00 for a 4.5 ltr/1 gallon sized can (£7.70 per litre) delivered.

I found a near identical 5 ltr can at Halfords for £21.00 (£4.20 per litre) specifically for Classic 1960’s, 70’s, 80’s cars. The only difference to the Duckhams can is the substitution of the name Duckhams with that of Halfords. Substantially cheaper with a £14 saving well worth it in my book as long as it is suitable for the job.

Not sure why but attaching pics changes the original orientation so just tap on the photographs to expand and turn the right way round.

[attachment=0]F990FC1F-7915-4F2C-A751-9BE6A58708D0.jpeg[/attachment][attachment=1]1B1E9350-8A35-41A0-8877-5398AA68F249.jpeg[/attachment]

Opie oils are currently selling 20 litres of Duckhams Q 20/50 for £94.99. Delivery is free by FedEx.
Just ordered mine!

Ian F