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To oil cool or not to oil cool that is the question
I am in the process of preparing the M20 2.5 engine which is destined for my Cabrio.
I am just debating if I should stick with using an oil cooler, I know there are arguments both ways, lighter car so less stress on the engine but on the other hand small engine bay so maybe higher operating temps.
I don't want to cook my nice new/exchange 6k mile M20 so an oil cooler may be the safest bet but I wondered if others had actual experience of the need for a cooler or not.
By the way if I decide to ditch the cooler, I had heard you can fit a filter housing from an M28 that doesn't use an oil cooler, anyone know if that is correct.
I fitted an oil cooler but I suspect it isn't really needed. My engine runs fine temperature wise when the car is moving - the only time that the engine temperaure rises and the cooling fan cuts in is when in a queue. The cooling fan has very little effect on the oil cooler - just the rad. So my reasoning is:
When you are moving the rad alone is sufficient. When you are stationary and could do with a little more cooling the oil cooler doesn't do much anyway.
I think if you were thrashing the car around a race track on a reguler basis the story mught be different...
The 2 litre M20 doesn't have an oil cooler but the 2.5 litre does. I presume BMW thought it was needed but maybe for country's with more elevated temperatures?
On the 2 litre M20 the oil filter screws straight on?
Yep engine was a result. Came from a BMW specialist in Sheffield called Quarry Motors. Two owners from new with fsh, every mot, receipt for 2300 pounds for exchange engine in 2003 then sorn certificates from 2004 to 2009 and I got it for only slightly more than 90/100k engines are fetching on eBay. Can't recommend them enough very helpful company.
Engine internals look brand new and it sounded great.
Theres a stat in the oil cooler connection so it will only use it when needed. Considering how big a rad and fan combo if ended up using to keep things stable I think the oil cooler is worth it. I have however not got the louvres all down the side of my engine bay.
I am using a Marlin crossflow radiator but even so because of the size of the nosecone on the Cabrio it is not going to provide more cooling than the standard BMW, maybe even less and the viscous fan has been dumped.
Like you I have no louvres so I think I will use a cooler although the original is too big so a 13 row mocal may be the best solution.
You can over cool the oil though, thats the problem, even with a 13 row.
If you do without, fit an oil temp sensor in the sump somewhere and keep an eye on it, check out the data sheet for the oil you are using and see what the operating temps are. If you do lots of track work then an oil cooler is probably high on the list of things needed but otherwise it's likely that it is not needed. If you feel a cooler is required then think about fitting an oilstat
The connection on the M20 has a stat built into it so it's only looped in when needed I actually bought a stat before I found out there was one built in anyway.
I assume BMW put the stat in the oil filter housing to protect against the possibility of the oil getting over cooled.
Given that the average 325 owner of the day didn't "track" their cars, it seems likely BMW must have thought that normal operation could require the oil cooler.
With the restricted radiator and engine bay on the Marlin I have come to the conclusion it is better to include a cooler.
It may be overkill, but not including one could prove expensive if it is needed.
I actually bought a stat before I found out there was one built in anyway.