I have a 2011 Ford fusion, 4 cyl. It sets for quite awhile, at times, so the battery goes dead from the electronics. I got it for that. I did try it on several v-8's, plus my slant six racecar with about 10-1 CR. worked fine, and so far it holds it's charge for a long time in the trunk. That's why I got the second one. I paid around $60-$70 if I remember correctly.