Oil and oil temperature

[Craigwilson]

Okay so I have a 91 8v as some of you may know, I recently changed my oil from Mobil 1 0w-40 to Castrol magnatec 10w-40 and with the Mobil 1 the engine only really reached 86 on the mfa and now it goes all the way up to 94 and 100 when I'm pushing it could this be to do with the oil in it.

Also my mixture isn't quite right could this be causeing it if It was slightly over fuelling ?

[jezza16v]

94-100 is about right, can go higher if you really push it. Overfuelling lowers the engine temperature, underfuelling raises it.

[Craigwilson]

ive read alot about these engines running up avove 90 but mine has always been between 82-86 even if im doing 100mph for a good 10 minutes it goes up to about 88 occasionally 90 but never hotter than that.

[Santiago]

Seems like it was too cool before, now it's just right.

As to why it's changed; seems unlikely to be related to your oil choice, as both are nominally the same viscosity at working temperature, only different at cold temps.

You haven't recently changed your coolant thermostat by any chance?

High road speed doesn't necessarily correlate with high temperatures, 'cos although the engine is working hard, airspeed through the radiator is also very rapid, so good cooling.

[Craigwilson]

I've not touched the thermostat in years but my mfa is lying because when I turn the engine off it jumps down about 16-20 degrees and back up when I start it again

[gazareth]

hey man as long as your oil light or buzzer doesn't come on it should be sound.

[Craigwilson]

I don't currently have an oil light and I'm not sure if the buzzer works

[gazareth]

i think to test the buzzer you disconnect the oil switch on filter housing and rev engine over 2000rpm to see if it sounds. im pretty sure that's how i done it but that was a couple of years ago. but it would do no harm to try and it only takes a second to pull wire of sensor. you could also stick a pressure gauge on end of cylinder head. tested mine recently and getting 20 psi at idle with engine hot. oil temp regularly hits over 100c to.