Oil hole requirement: diameter＞6mm / curvature＜30°, Package weight: 405g / 0.9lb, Package size: 250 * 210 * 60mm / 9.8 * 8.3 * 2.4in, Detection type: turbineoil, Battery: 4 * AAA battery (not included), Color: yellow, Total height: 170mm / 6.7in, Hose length: 800mm / 31.5in, Probe diameter: 5.3mm, Material: ABS.
Basically copy coupon, view price history or create e-mail price alert. Do you want to know what the best price is?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
1. ($36.95): BGSCM75
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGe6f973
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Price history (for all/most countries) for Engine Oil Tester is here. The lowest price was: $32.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).