Just purchased vintage trailer. Need help.

Does the trailer have electric brakes? Might have surge brakes.1965 might not have electric brakes.

 

Yup. Big heavy box. How fast did you drive? In what gear?

Towing mileage will never be great, but towing anything over about 60mph / 100kmh really sucks your tank dry.

Off topic: the young lady in the picture... I've seen that smile on my wife's face before. It says "this is another one of his ideas...."

 

Good question?

 

I was driving around 50-60 mph on mostly flat road. It stayed in 4th most of the time with an occasional kick down to 3rd (which it seemed to hold too long). Every time my Eco app updated it showed around 10mpg. When I got home most of my eco bars were level at 10mpg.

 

All of that sounds about right. I will say, just based on your truck's "reaction" your trailer is damn heavy.

 

This might help as well.

https://www.tacomaworld.com/threads/brake-control-install-write-up.428999/