5-30 synthetic oil

[MikeNash]

What ho, me dearios!
I need your advice. An abiding interest of mine is in reducing the fuel consumption of my 1963 1098cc Traveller which is typical in generally being in the upper thirties to the gallon and which with a little care I can stretch into the lower forties. My focus currently is reducing the internal friction of the engine by lowering the engine oil viscosity. Like most Minor owners, I suspect, I’m using an SAE 20-50 grade (using up the last of my Wilkinson store brand) but I’m thinking of moving to a 5-30 synthetic. Of course, there’s nothing wrong with 20-50 grades, indeed, I’ve used them since they became popular in the 1960s (especially the Duckham brand; see a history here https://www.duckhams.co.th/data_sheet/D ... y-Book.pdf). And further, my latest Workshop Manual (Publication Part No. AKD 530 (14thEdition)) recommends SAE 20-50 for all temperatures above minus12C. But I note that in my earliest Workshop Manual (Part No. AKD530B Issue 2 19997) SAE 30 & SAE 20/30 (Esso Extra) are recommended for the same temperature range, and if you scroll down in the Duckham history link above you’ll see on page 94 a Minor Lowlight(?) engine bay with a can of Duckham’s 10w/30 clipped to the firewall. So, my rationale for thinning down to SAE 5-30 synthetic is that originally SAE 30 was specified and then 20-30 included, and while these was overtaken by SAE 20-50, if the original design envisaged SAE 30 as the prime oil, then its superior modern equivalent should be even better.
If you scroll down to the graph shown here; https://www.widman.biz/English/Calculators/Graph.html you can see the difference at lower temperatures as well as the advantage when the oils reach the 50-60C mark. Quite how viscosity translates into friction I can’t find out, but the A Series engines are big for the power they deliver and so their internal friction is probably an important influence. Clearly, the graph shows that getting the oil above 60C helps a lot, but for me, this takes some brisk driving for some 25 miles or more on a hot day to get it. (Shielding the sump and heating the oil will be in a future thread.)

Of course, a lower viscosity oil will give lower oil pressure readings for any given engine speed and oil temperature, and for those with a gauge, high readings are generally considered “a good thing”. However, this thought needs care; the oil pump pressure relief valve opens at about 60psi and then short circuits some of the oil supply back to the sump. This means that if you’ve a gauge reading of 60psi or more a good deal of your oil is not going around the engine. (On a first start at below freezing my engine running at the raised idle given by the choke will show 70psi with a relief valve that opens at about 55psi.) Another reason, I think, for reduced viscosity at low temperatures.

A final point; at lower viscosities the oil flows more easily through the oil filter so there’s a reduced pressure across it. This is important ‘cos when the oil pressure across the filter rises (as it will do as it clogs) to about 3psi the filter bypass opens so unfiltered oil passes direct to the engine. (And I bet this is happening on cold starts.) Our Phil has suggested here viewtopic.php?t=77199 (at Mon Feb 12 2024 12.24 pm) how this bypass may be blocked but I fear that with a thick oil a high pressure may result across the filter raising the risk it might burst and dump its collected debris straight into the bearings. Another plus for a thinner oil.
So, all in all, I think my change to a SAE 5-30 synthetic is a good idea. What say you? Regards from MikeN.

[philthehill]

Mike
I do not think that I would go so far as to use a 5W30 fully synthetic oil in a 'A' Series.
The rear scroll may not be able to cope with returning oil to the sump.
My Honda Jazz uses 5W30 fully synthetic oil in the engine but the machined clearances are much more precise in the Honda engine and lip seals used everywhere.
As regards a modern engine oil for a Minor 1000 I would use a 10W40 semi synthetic oil for ambient temps over 10 degrees Centigrade. The comparable Marina 'A' Series should use a 5W30 (semi synthetic oil) for all ambient temps below 15 degrees Centigrade and a 10W40 (semi synthetic oil) for ambient temps of above 5 degrees Centigrade. Data taken from BL drivers handbook AKD7554.
I agree that a good quality modern day synthetic or semi synthetic is much better for engines generally than a mineral oil i.e. 20W50.
Here is a good read
https://www.calverst.com/technical-info ... s-and-how/
Shutting off the oil filter bypass valve is a well used modification and I have never heard of a filter disintegrating with the valve blocked off. The oil pressure relief valve is before the oil filter so any back up of pressure will disappear past the oil pressure relief valve to the sump. The relief valve dump gallery is of a sufficient size to allow the maximum flow of oil to dump to the sump without causing backup. The relief valve spring can always be set on the lower end/scale of the required oil pressure if problems are perceived. Too much oil pressure is nearly as bad as too little oil pressure. Too high a oil pressure generates heat and saps engine power.

[Myrtles Man]

Additionally, the following Q & A session relates specifically to engines such as those in Moggies:-

https://classicmotorsports.com/articles ... ecord-str/

[geoberni]

There's some good answers here already.
I'm of the opinion that some of your assumptions are flawed; for example your observations about differences the oil recommendations between the AKD530 issue 2 and Issue 14, probably some 20+ years apart are easily explained.

When the Minor first arrived in 1948 there was no such thing as Multigrade Oil. They were all 'Straight Oils' well into the 50s. There was no Multigrade.

Kendal Oil in the USA claim to have marketed the first 10W50 in 1953, it wasn't widely available until towards the end of that decade.
So Morris couldn't recommend 20W50 when your Issue 2 was in use.

I'm by no means knowledgeable about Oil Grades, but I think you're on a complete wild goose chase with the numbers here.
Using your own argument about the original grade being SAE30 'so why not...?' , then why not now use 10W30, or 20W60??

[kevin s]

Assuming it's in reasonable health I'd give it a try and see what happens, I can't see it doing any great harm. Only thing I would think about is adding a ZDDP addative, most modern engines don't have the sliding surfaces of an older design and ZDDP help with this, it also helps with friction which will help your fuel consumption.

Some sort of modern low loss tyres would also help.

[Peted7202]

5W-30 Motor Oil
5W-30 oil is best for vehicles that are regularly driven in colder climates where temperatures can fall below 0 degrees Fahrenheit. It is a light oil that will circulate through an engine faster than a more dense grade and is designed for use in colder climates where cold engine starts are common. It is generally recommended for new and high-mileage vehicles under all weather conditions.

20W-50 Motor Oil
Due to its high-viscosity, 20W-50 is suitable for hotter climates. It is highly recommended for older vehicles. The oil's density helps protect aging engine parts and helps prevent leaks that are common with older cars.

[MikeNash]

Thank you to Phil and Myrtles for the links to those interesting sites, and also for Phil's points on the filter bypass valve.
Regarding Geoberni's point that the different "recommendations between [the two Workshop Manuals that are] probably 20+ years apart" is to a large degree my problem. As you say, there were hardly any automotive multigrades for the ordinary owner in the 50s; I know, I was there, and then quite suddenly 20-50s swept the board, esp Duckham's. I suspect it was also fashion thing (it certainly was amongst us lads) but today I remain fairly convinced that the earlier SAE 30 was the design lubricant. As to your point of "why not 10W30 or 20W60, well the answer is that the right hand number (here your "30" and the "60") denotes the viscosity of the oil at 100C, which is about the temp seen in a hot, hard working engine. (Note, the numbers bear NO relation to the actual viscosity; this is VERY important.) I believe that the earlier SAE30 of yore gave the designed protection at this high temperature, and while 10W/30 will do the same, why have it thicker at low temperatures if SAE5/30 is easily available? Likewise your suggestion of 20W60. At least one Minor that toured a good deal in Europe using a warmed 1275 and described here in the past has used it (alas, I forget the owner's name), but I see no need for it in an unmodified road machine.
Regarding Kevin's point of ZDDP additive, that's a continuing concern for older engines and one I've no answer to. I'm against additives in general but have to admit that long ago I found Molyslip essential in a fast aircooled sidevalve (a Matchless powered Brough) and so I try to keep an open mind.
What Peted7202 says is true for most modern engines but I remain dubious of the recommendations regarding 20-50 on older vehicles. Leaks I try to cure by better sealing, and still don't understand the lubrication argument. Overall, I think I'll give the SAE 5-30 synthetic a try and also try to mark closely any changes it brings about and report back, both regarding wear and performance.
Thank you all for your comments, even those I've disagreed with: they made me think further and more carefully.
MikeN.
PS Apologies for my late reply; I had to help in a family transport crisis. Apparently that's what grandfathers are for.