Difference in Coolant/Oil temp

[Djrystofer]

I've recently bought a bmw for a steal,
However it has a quite minor issue. It's Thermostat is stuck most of the way open, so the coolant never actually goes over the quarter way mark unless it's been sitting idle for a while, in which it does start to get a bit hot (as the thermostat is only partially stuck open)

I'm just wondering to the people who maybe have had the same issue, is this damaging the motor running cool? Does the oil get up to temperature, even though the coolant is still cool?
cheers

[Trump]

Oil and coolant are completely separate. A partially open thermostat is good for your engine as it doesn't experience a form of thermal shock when the thermostat opens. The one downside is you will use a bit more fuel during warm up as the ECU/PCM is in open loop mode (richer during warm up) for longer.

[Djrystofer]

So is it safe to assume that the oil gets up to a somewhat safe temperature for proper lubrication, even though the coolant is cool?

[4VCLEVO]

I highly doubt the BMW engineers are fools, if they thought that having the thermostat partially open would be good for the engine, they would have designed it that way. If you picked it up for a steel, then you should have a few bucks left over to replace the thermostat and have it working the way it was designed to.

[MrEL]

Originally Posted by Loud_Noises

Oil and coolant are completely separate. A partially open thermostat is good for your engine as it doesn't experience a form of thermal shock when the thermostat opens. The one downside is you will use a bit more fuel during warm up as the ECU/PCM is in open loop mode (richer during warm up) for longer.

Which dilutes your oil with unburnt fuel.
You want the motor running at correct operating temperature ASAP.

[Djrystofer]

Originally Posted by 4VCLEVO

I highly doubt the BMW engineers are fools, if they thought that having the thermostat partially open would be good for the engine, they would have designed it that way. If you picked it up for a steel, then you should have a few bucks left over to replace the thermostat and have it working the way it was designed to.

'stuck open' as in, broken.

Obviously I'm going to change it very soon, I'm just curious to know what implications this has on the life of the engine, as god only knows how long the previous owners have left it like this.

[mik]

don't know what state you're from, perhaps it is just plain cold outside and the motor is not getting higher in temp for that reason?

[noflac52]

Oils (like everything else automotive) are designed to work best at certain temperatures. If the oil is at a temperature less than what it is designed to run best at the lubrication is not at its optimum and accelerated wear of components will take place. Its not as bad as an engine running too hot but it will wear an engine out quicker than when everything is at the correct temperature.

If the engine is not showing signs of wear it will probably be ok for quite a while yet, just get everything working at its correct temps using correct thermostat and correct oil and it should be fine.