Tow Weights & Car Performance

Davidwa

I am fairly new to caravanning, am towing my small caravan (1000kgs MTPLM) with a 2.0 Diesel ix35 and  get about 30mpg. 

I want to upgrade my van to a fixed bed model but want to keep the length and weight to the minimum. I have looked at a couple of van choices, one had an MTPLM of approx 1200kgs and one an MTPLM of 1385Kgs. 

I am assuming I am packing the Vans to their max user weight and realise both weights are fully within the towing capability of my car.  

How will adding 200Kgs or 385Kgs to my current towing weight affect the performance of my car. Will my mpg drop considerably or will I hardly notice the extra weight.

 

If anyone has experience of this I would appreciate your input.