1996 Rav4 not warming up properly when driving and heat not hot

1996 Rav4 not warming up properly when driving and heat not hot

I have a weird problem. I recently changed the radiator and flushed the whole coolant system during replacing the radiator. I also flushed the heating core by itself. The thermostat was recently changed and it doesn't seems to be stuck open because if the car is sitting it warms up properly. The coolant temperature sensor was also changed recently because the temperature gauge would start in the middle and that seemed to be the solution to that problem. 
The problem:
When I start the car and leave it sitting, it warms up properly and stay at 1/2 of the temperature gauge. However when I start driving the temperature gauge drops a lot. Most of my commute is on the highway and most of the time the temperature gauge stays at 1/8. This mainly affects the heat, right now if I leave the car sitting the heat works great but once I start driving on the highway it is not as hot. 
I talked to an employee at Autozone and he told me to make sure I burped the engine. From what I am reading online the car would be over heating if it was not properly burped. But it can't hurt to try, so I plan on getting a lisle funnel soon. 
Any other solutions or ideas of what the problem might be?
Thanks!!!

Solutions/Answers:

Answer 1:

If the thermostat is stuck open, you would get the symptoms you describe. A thermostat stuck closed will cause overheating.

Answer 2:

One possible explanation is that some coolant is bypassing the thermostat altogether.

Depending on the thermostat and seal arrangement, this could happen if the thermostat isn’t properly seated in the surrounding seal, or if the seal is compromised and not doing its job properly.

It would also explain to some extent why the thermostat seems to work when the car is stationary but not when the car is moving. In highway driving, the water pump runs faster, pressurizing the coolant more, which allows more cooalnt to leak past the thermostat.

Answer 3:

Did you replace the radiator with OEM or aftermarket? It almost sounds like the new rad has more surface area and it cooling at speed better than the old one did.

References

2006 Toyota Prius in Africa

2006 Toyota Prius in Africa

I am an economizer, especially when it comes down to my transport expenses.
So I live in Tanzania (Eeastern Africa), we have no electric vehicle recharging stations, not so many EVs around here,
I am planning of buying a used 2006 Toyota Prius
model code - DAA-NHW20
I want to buy this car due to its fuel economy as everybody seems to talk well about it.
There are no charging stations anywhere near where I live. So would I achieve 50mpg running completely on gas ?

Solutions/Answers:

Answer 1:

That model of car can’t recharge from a charging station. It charges the battery either from braking or by using the petrol engine as a generator.

So yes, you should in theory get the 50mpg without a charging station.

However it can depend. I have no idea of the type of driving and the quality of roads you’ll be driving on. Most of the benefits come about because in normal city driving in Europe/USA/Japan, the markets the car was originally designed for, a lot of energy is thrown away in the brakes under relatively gentle braking.
If the roads or driving style mean that this doesn’t happen then you lose a lot of the benefits.

Also the batteries in a 10 year old electric car will be 10 years old unless they have been replaced. That means they will have a greatly reduced capacity which will have an impact on fuel economy but I have no idea how great this will be.

References