JCB 3CX engine oil 15w-40 or 20w-50

[SimosSoldatos]

Hi everyone, i have a 1990 3cx with a turbo diesel perkins 4 cylinder (perkins t4.236) and the manual for it recomends 15w-40 for the temperatures i use it in but some people use 20w-50. Any ideas why and what do you guys think is best for it? Would the 20w-50 which is thiker be better for it since it's a pretty old machine (6500hrs)?? Thanks in advance!!!

[Slooby]

I run 15W40 Mineral oil in mine, but it's a 1987 N/A 4.236.

I'd stick with what the manual recommends for you engine, unless you notice that you're burning through a fair bit of oil at which point the heavier weight oil might help out. You have to be careful on whether your engine is up to running a more modern semi-synthetic oil as the detergents can cause issues in engines designed around mineral oils and some of the seals can struggle too. There are some Perkins manuals in the downloads area here and elsewhere on the web that based on the engine serial number could give you more details on what the engine is happy to run on

[SimosSoldatos]

Thanks a lot for the response! Never thought about wheather or not i should be using modern oils, i'll definitelly look into it.

[essexpete]

I would also go with what the manual says. I use a 15W 40 mineral in a multitude of engines from 1989 to 2004 vintage. I think some really old engines from the 50 and 60s may be better suited to an old fashioned single sae grade. Very modern engines, with sophisticated (and bloody annoying) emissions control, may need specific oils.

[SimosSoldatos]

Well, looking through the manuals here perkins recomends both 15w40 for temps from -10 to 50 celcius and 20w50 for -5 to 50 degrees so looks like any of the two should be fine. I'll probably go with the 20w50 being that it's an older machine but i'll look into mineral oil since both you guys recomended it. Thanks a lot!!!

[gecko.cx]

The thicker oil will have a greater resistance to passing the rings (and burning) if the rings are sloppy.
Similarly, if the bearings have excessive clearance, the thicker oil will hold pressure better ..... but -

The trouble with thicker oils is they are hard to suck and the oil pump has to suck it in before it can pump the oil and raise the pressure. The longer the the engine cranks /runs without pressure, the faster it will wear.

So, unless your engine is already on the way out and you are just postponing a rebuild, I'd be running 15W/40 (I do run 15W/40!)