It depends on what you mean by safe.
If you drive and corner at high speeds with 5 obese passengers in high heat (or would it be low heat?) and rain you have a different threshhold of what is safe.


My tirewalls say max is 44 psi
My doorjamb says 32 PSI
I keep mine at 40 PSI

You have to find your own personal comfort level.

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.