I have had the old GM card for about a dozen years. A few clarifying thoughts:

1. The "old" card is capped by $500 per year, up to 7 rolling years, so it is possible to put 8 card years of credit onto it for $4000 towards a GM vehicle. Newer cards issued, I'd say in the last half-dozen years, have vehicle caps considerably less than this.

2. GM Card literature has always encouraged negotiation prior to revealing payment using the GM Card earned credit. This is what I did.

3. The car I purchased 5 years ago I was happy to find that sales tax was not charged on the value of the GM Card credit of $3500, saving another ~$250.

This is definitely not for a lot of people as you need to buy a GM car. On the other hand, if you have the "old" card, ~5.36% return for spend is good enough for me to buy one every 7-8 years for someone in the family.