If you asked 10 average car people whether they wish they had a significant other who enjoys a 12mm box end wrench in one hand and a droplight in the other, they would shrug and reply, "I'm being realistic." Sadly, car enthusiasm is rare enough that finding someone who satisfies all your other needs and loves cars can be one too many criteria to place upon that special someone.
According to YouTube channel Crossthreaded, however, turning a project car into a couples' activity may be simpler than you think—it's just a matter of healthy relationship dynamics.
The first tip to keep in mind when trying to coax your significant other into the garage is, in the words of co-host Megan, is "Don't be an asshole about it." Making fun of someone for not knowing the difference (or lack thereof) between a 5/16" and 8mm wrench isn't going to make them enjoy using it, and it makes you look like a tool. Remember learning to grill or bake with your parents? They didn't make fun of you for not knowing when to flip the burger, or how to check if a baked good is done with the toothpick trick.
The second thing to keep in mind is reciprocation. Your special someone may be more inclined to do what they consider your thing if you volunteer yourself to try out their hobbies. If they're a hiker or a salsa dancer, offer to go with them. They may in return want to see if they can help you out with your car, even if it means holding the drain pan.
One final thing to keep in mind is that sometimes, they just won't have any interest in crawling under a car. Germaphobes fit under this umbrella, as would anyone who has early joint problems or even metal allergies. There are many reasons why your significant other may not ever want to help you out in the garage, and that's normal. But if you can't accept that fact, then...well, there are other fish in the sea, as they say.