Hello everyone. I am doing some exploratory analyses which requires estimating different model specifications. Please, how do I replace predicted values from an old regression with predicted values from a new regression without having to generate another variable. Here's what I mean:

Code:
sysuse auto.dta
I estimate the following regression

Code:
reg price mpg mpg weight
And compute the predicted values

Code:
predict phat, xb
Then I run another regression

Code:
reg price mpg weight foreign turn displacement
Attempting to generate phat again results in the error

Code:
predict phat, xb
phat already defined
r(110)
Please, how can I generate phat that overwrites the values of the existing phat each time I estimate a different regression?