Buying for a car guy/gal/mechanic is like buying for a musician, they have pretty specific likes and dislikes where tools/gadgets are concerned and unless you really know your target you have to be generic with your gifting strategies. 

Here are some ideas to get you started:

https://shop.snapon.com/gift-card (at least $250 will get him/her something nice)

https://blog.matcotools.com/top-10-mechanic-gift-ideas-for-the-auto-tech-who-has-everything

Around $20 Pocket Flood Light from Matco:
https://www.matcotools.com/catalog/product/MPL200O/pocket-flood-light-orange/

Around $20 Pocket Flood Light from Snap-On:
https://shop.snapon.com/product/Specialty/COB-LED-Pocket-Flood-Flashlight-with-Laser-Pointer/ECSPB023O

Home Depot has digital and traditional gift cards:
https://www.homedepot.com/c/Gift_Cards (at least $250 will him/her something nice) 

$40 390 Lumen Magnetic Slim Bar Folding LED Work Light:
https://www.harborfreight.com/390-lumen-magnetic-slim-bar-folding-led-work-light-63958.html

Harbor Freight Gift Card: https://www.harborfreight.com/gift-cards (at least $100 will get him/her something nice)

Rock Auto Gift Cards https://www.rockauto.com/en/tools/?parttype=260

Solid car starter:
https://www.amazon.com/dp/B015TKUPIC/ref=cm_sw_em_r_mt_dp_U_Zfv6Db3Y4V0XE

Motorcycle Gift Ideas: http://www.rollingthundercycles.com/page/288960205
http://www.rollingthundercycles.com/product/P38120040

From Automoblog:

https://www.automoblog.net/2019/11/11/best-gifts-for-car-guys/

From Chris Fix:
https://youtu.be/DvcpqCPQ3uI

From Blue Devil Products:

https://gobdp.com/blog/antifreeze-color-use/

From Automoblog:

https://www.automoblog.net/2019/01/03/winter-driving-101-the-complete-guide/

I was watching a promotional video by Eric the Car Guy where he was talking about the 1/2 price promotion for Haynes manuals. I went to their site and ordered them for 3 of the family cars. If you need one this is a good time to look into a purchase. Oh yeah, there's free shipping on print manuals too:

https://haynes.com/en-us/?utm_source=ericthecarguy&utm_medium=youtube&utm_campaign=blackfriday