Why is my ford escort van costing me so much money??????

It's a ford escort diesel van 1994. Struggles uphills. Lorries overtake me. £15 quid of diesel only gets me 80 miles.

Ive changed fuel filter, air filter, air in tyres, oil change, ....even took the roof rack off. Return pipes are ok.....dont really know what else to look for....


Is it just knackered or is there anything else i can do for it...

please help!
Helen