Dave I wouldnt for three distinct reasons:
1) Through my local credit union I can get 1.9% on auto loans...I cant get that good on a HELOC.
2) Most dealers have stupid incentive games to finance with them, you will likely pay more if you finance third party..unless you just like the negotiation and trick game.
3) This is the big one...I always plan for the absurd. If the worst case scenario happens. You could end up forclosed and evicted from your house for not paying your car payment. We never plan to be there but sometimes shit happens. With a stand alone auto payment if shit happens worst case sceanroio they repo your car. In a HELOC it is a foreclosable position....I know I know "Wont happen to me" Id just refi it" etc. What if you lose your job and have a major injury/illness in a short time span, cant get employed and therefor cant qualify for a new loan. We can what if it to death...but for me...I wouldnt do it. You are free to do as you see fit.
