temp gauge jumping about
 

My son's temp gauge on his 85 240D has been erratic. I'm thinking a bad connection at the temp sender. Any other ideas?
Also his fuel consumption seems to be horrible as of yesterday. I thought maybe a sticking fuel sender which might show lots of fuel and suddenly take a dive when the tank empties. Any thoughts here? Who's been there?
Mike

Jumping temperature needle is either a bad ground or a bad sender (Located between the #2-3 cylinders on the head).

What is the actual MPG?

I don't know the milage because I don't drive it. I'll have my son do a fill, drive and refill and chart the stats. Thanks.

Check the wire connection at the block sensor, it may be broken or ready to break. Mine just did this, I had to resolder the connection, now no jumping. Keep notes on the mileage for fuel consumption, you will soon find out how far you can go. Good luck.

Another possibility is the engine to body ground strap.