over cooling!

[mak]

now its geting colder i've just started using the heater over the last week and its made a massive diferance to the temperature gauge so much so that a steady 80 on the motorway with a slight chill and the heater on my temp gauge actually droped to 50 and its not faulty because the oil presure went up to suite. am i right in thinking the 5ltr cars will run cooler than the 4's.
cheer's.

[shpub]

No 5 litre cars run slightly hotter if anything. Just cos the oil pressure remained high doesn't mean the temp guage is not a bit dodgy. Usual cause is airflow causing the temp guage to misread or cool the engine as the colder air flows over it. Can also be caused by a stuck open thermostat as well.

I would start by chceking the guage and goiung from there. There is a whole chapter on this in the bible.