When the Morris Oxford was first introduced in 1913, engine oils were classified into gradings such as light, medium, heavy, xtra heavy and each manufacturer basically had their own thoughts as to what dictated a light oil and what was a heavy oil. Oils were heated in glass tubes to a certain temperature (100 Degrees C) and times were recorded in seconds how long it took for the oil to flow down the tube. From here a thickness or viscosity could be worked out.
During 1926, The Society of Automobile Engineers (SAE) devised a Crankcase Oil Viscosity Classification System and designated oils into categories or grades. These grades then became known as monograde or single grade oils with such gradins as SAE 20, SAE 30, SAE 40, SAE 50, SAE 6O.
In many, of the handbooks right up to the 1960’s, you will find that when looking for oil recommendations for your vehicle, you will see mentioned two grades one for summer use, and one for winter use. For example a SAE 40 oil for Summer conditions and a SAE 20 oil for Winter conditions. When we look at what was recommended for a Morris Eight of 1939, we see that for Summer use one should use a SAE 50 oil and for Winter, a SAE 20 oil should be used, but bear in mind this was recommended for UK conditions and not for Australian conditions. There is a huge difference between the two grades in terms of thickness/viscosity. In Australia the recommendation called for a SAE 30 oil for all year use.
If we have another look at the recommendations as specified for a Series MM of 1950, we see that for Summer use a SAE 30 oil is specified, and for Winter use a SAE 20 oil is required. Again these recommendations were for UK conditions.
Getting back to our SAE grades for a minute, one would have thought that this was going to be a fairly simple procedure to follow, but like most things in life it did become complicated. Oil companies have always devised names letters, and numbers to designate various grades, and if you look at a chart of the time, you will see such things as Castrol XL, Single Shell, Castrolite, which then meant you had to a quick cross reference to find the right grade. This system carried right through to the sixties when multigrade oils came into place. This is at the time of the late Morris Minor 1000 models and the introduction of the 1098 cc engine. There were a lot of problems associated with single grade oils, the main one being a significant drop in oil viscosity when the oil was hot. There are many people today who hold the belief that their newly restored 1950’s vehicle having run on a SAE 30 oil from new should in the 1990’s again run a SAE 30 engine oil because that is what the book says. If they are after 1950’s technology then that’s fine but as you will see we have come a long way since then. (you don’t suppose it’s worth any more concourse points?)
We now move into the swinging sixties and the advent of multigrade oils. What happened was this; By treating a SAE 20 oil with a viscosity improving additive, this then had the effect of decreasing the loss of viscosity with temperature (the problem associated with single grade oils) and when measured in the laboratory at the set temperature of 100 degrees C, produced the same viscosity as a SAE 50 oil. This then became a 20w/50 oil or more commonly called a multigrade oil. The “W” signified the Winter grading left over from days gone by. Other grade came into being such as 30w/40, 20w/40, but in actual fact in Australia 20w/50 was basically the standard grade.
I happen to have in front of me a Shell book of the mid 1960’s, which relates to Australian conditions. The book states that the “new” 20w/50 engine oil can be used to replace SAE 20,30,40,and 50 grade oils, and yes the recommendations for a 1966 Morris Minor calls for a 20w/50 type engine oil. Shell incidentally went one step further and developed a 20w/40 just for good measure.
Having said all that, I now want to have a quick look at rear axle and oils, because along with engine oils, they too underwent quite significant changes.
In a nutshell basically what we had in the early days were straight grade gear oils with viscosities of around 90, 140, and 250 grades. In the 20’s, the American car manufacturer Packard introduced a new rear axle design called the hypoid axle. Basically what he did was to alter the position of the pinion gear thus giving the tooth of the gear a sliding contact as well as rolling contact. Having achieved this, it was then necessary to incorporate additives into the oil to protect the teeth from wear. These types of oils became known as EP or Extreme Pressure Gear Oils.
This type of rear axle design became the norm and was particularly welcomed especially with the coachbuilders of the day who could now build bodies without having to worry about transmission tunnels and propeller shafts when designing rear floor space.
These types of oils were used in these early forms of hypoid rear axles right through to again the early 60’s including the Morris Minor range where upon they undenvent a change to become what we know today as Hypoid 80w/90 gear oils. The useful cut off has always been 1960.
Now for a word of WARNING.
The early forms of hypoid rear axles contained a lot of brass and bronze of which the additives used in the oils were quite compatible with. In hypoid type rear axles today, the additives used do not get on at all well with yellow metals and start attacking them with relish. It is therefore important not to put modern hypoid gear oils into early hypoid rear axles.
On the subject of gearbox oils, Morris went the same way as most other English manufacturers and stipulated engine oils for gearbox applications. The reasoning for this was probably that if it was good enough for the engine, then it should be good enough for the gearbox as well. This was fine then, but today why not use the correct oil for the correct lubricating need ? In other words use a gear oil.
You are now all probably totally confused lost interest or have gone to slit your throats, so I’II quickly put on my Penrite cap and try to steer you through this landmine.
First things first, forget the idea that old cars need thick oils. There is absolutely no need for any Morris in this country to be running on anything thicker in the Penrite range than a 25w/70. If you have a vehicle on HPR 50 in particular over Winter then I would suggest you have an oil change and go down a grade to HPR 40 25w/70. My particular worry is with oil pump drives having to cope with a thick oil when cold. A 25w/70 offers better pumpability when cold, but offers the same protection when the oil is hot as HPII 50. This also applies to cars which are suffering from acute oil consumption problems.
For Morris’s in good mechanical condition, then HPR 30 20w/b0 will be the standard grade all year round.
For gear oils, may I suggest our Gear Oil 30 and Gear Oil 40 which will cope a lot better in a gearbox than a engine oil will. It will also make changing gear a lot easier particularly in cold mornings. For rear axles as I’ve mentioned already do not use a modern GL5 rated Hypoid gear oil in an early rear axle that would normally have taken a EP gear oil. By the way, these early gear oils were often listed as 80,90,140 grades, with words such as “Spirex”, “HD”,”EP”,”Hypoy” etc. Rack and pinion steering takes the same oil as the rear axle and NOT a heavy grease.
On the fickle subject of radiator products may I suggest a corrosion inhibitor rather than a Anti Freeze-Anti Boil type product, and may I go one step further and suggest a non glycol type inhibitor. In cars with thermo syphons there is no point having a anti freeze type product because you don’t possess a thermostat. if you wish to use the glycol type products on the market, then for old Pete’s sake make sure the dosage is correct. I think I have rambled on enough, so I will now close with the simple words of thank you and happy motoring.