When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I made a stick out of wood and have marked the full level. I just reach in beyond the spare tire, open the lid to the tank and "stick it". If going on a long drive (1000 miles or more), I sways go ahead and top her off. And if I have to add fluid, I always remove the spare, as it makes access and filling easier and clean up after spilling some (yup, always a little cleanup) after filling.