What oil should I use?

What Oil should be used?

We are often asked why a particular grade of oil is required. This is largely dictated by the evolution of engines, transmissions and hydraulic systems; for example, the appropriate lubricants for a TVO Cropmaster are a world away from that needed for a tractor built in the current century. There are many reasons for this.

Materials used within the engine have evolved; additives in modern oils can attack materials such as bronze that may no longer be used in newer tractors. Running clearances, the ‘slackness’ between bearing surfaces such as those on the crankshaft are now much more accurate. This enables the clearance to be reduced without risking them being too tight. The clearance space is taken up by a film of oil; greater clearances on older engines require thicker oils. Service intervals were much more frequent on older vehicles. The oil degraded more quickly and needed to absorb more carbon, a by-product of combustion. Again, this is because the running clearance between the pistons, its rings and the cylinders are a closer fit than they used to be, reducing “blow by”, hence power loss, increased oil consumption and contamination. Modern fuels also burn more cleanly, too; all these advances facilitate extended oil change intervals. However, this does require more expensive, higher specification oil, though it’s a small price to pay for extended oil change intervals, and the fact that modern engines rarely need rebuilding. With all the above said, service intervals aren’t really an issue with our vintage tractors as they are unlikely to be clocking up many hours work. For those of us restoring a tractor a bigger issue is “running in” a newly rebuilt engine properly. Modern engines don’t usually require this, again due to the accuracy of their construction. With our older engines, piston rings need to “bed in” to the cylinder walls. The use of running in oil for a while is important because it deliberately excludes anti-wear additives that would prevent this. Together with a failure to work the engine reasonably hard at running temperature this can lead to glazed cylinder walls. Being too shiny to retain a film of oil, the result is excessive “blow by” to the point of throwing oil out of the exhaust.

Types of Oil

Monograde or Multigrade? Before we discuss this subject, a little explanation on “SAE” grades. Introduced by the USA based Society of Automotive Engineers in 1911, it is a standard system for grading oil viscosity (thickness), commonly ranging from SAE10, which is rarely used, to SAE 140, a heavy gear oil, as used in some David Brown final drives. Multigrade oils have two ratings, for example, our Universal oil, SAE 20W/50. The W (winter) denotes how well the oil flows when cold; the figure following the “W” gives the flow characteristic when hot. This characteristic is mainly aimed at engines, though in most cases it can also be used in the transmission.

What David Brown Recommended

Monograde oils were the norm until the 1960’s, simply because multigrade oils were only just becoming commonly available. With monograde oils a different viscosity (thickness) was recommended for different temperatures. In the UK this was usually SAE 30 for winter use and SAE 50 for summer use. Where temperatures are consistently below -7 degrees C. the use of SAE 10 was advised. In the UK, it is probably best to simply use SAE 50 unless you intend going out in sub zero temperatures! One of the issues with using an oil grade that’s too thick was that it made starting more difficult, but unless tractor has to be started by hand this isn’t an issue as modern batteries are more powerful than their predecessors. Another advantage of using SAE 50 is that it can also be used in the gearbox and air cleaner bowl.

From the late 1950’s/early 1960’sMultigrade oils were generally recommended by David Brown, so roughly Implematic onwards. Our SAE20W/30 can be used in all David Brown engines and transmissions up to and including Meltham built 94 series tractors, except those with turbocharged engines. Due to the higher stresses involved these need the higher grade “All Farm” SAE15W/30 oil.

Final Reduction Units

The final reductions, inside the rear wheels, should be filled up to the level plug with SAE140 oil on all David Browns fitted with drum brakes. This should not be SAE140EP (extreme pressure), as this is a more modern formulation containing additives that may attack some parts used in these final drives.

The exceptions to the above are the larger tractors – 1410, 1412, 1490, 1690, 1494, 1594 and 1694. Universal SAE 20W/50 is the correct oil to use on these tractors as they are fitted with oil immersed disc brakes; note that this oil needs changing at the intervals directed in the operator’s handbook. This is because it becomes contaminated with the friction material from the discs as they wear. The rate of wear depends on how much the brakes have been used; unlike drum braked David Browns, where brake squeal is a normal characteristic, on these tractors it is an indication that the oil needs changing.

Four wheel Drive Front Axles

This is the only application where “EP” oil should be used. Our SAE90 EP is the correct grade for this application, both the centre section of the axle and the front hubs.

Power Steering

If fitted, this uses a hydraulic mineral oil; our Hydraulic oil HM ISO 32 is appropriate. Note that the main hydraulic system uses the transmission oil, as this also lubricates the gears and bearings hydraulic oil isn’t suitable.

Clutch and Brake Reservoirs

Most tractors with a hydraulically operated clutch and braking system use mineral fluid, classified as LHM. Our part number for this is 41414. DO NOT use car type brake fluid; it will attack the control cylinder seals!

The exceptions are “Highway” tractors, as the front wheel brakes require DOT3 or DOT4 brake fluid, which is a vegetable type, as used in most cars. This includes early versions, such as the 880, that have mechanically operated rear brakes with just the front brakes hydraulically operated. Later Highway tractors equipped with both front and rear operated hydraulic brakes also use this type of fluid. In these situations, the transmission clutch control uses the same fluid. Again, using the wrong fluid will damage the seals.

As always, if in doubt, contact us for advice!

Check out our range of oils here. Lubrication