There's been some long threads on this topic. And there's a LOT of different answers, but the biggest problem may be the water you're using to wash the MF's. Seems there's soooo many minerals in tap water, they tend to cling to all fabrics as they dry. This forms a barrier preventing the fibers from picking up water immediately. Funny as it seems, you may find the towel works better if it's been wet, wrung out hard to damp and then used to dry the car. That's because the wet minerals are no longer a barrier and the fibers can absorb water.
Try this to see if it is your water; Get a couple gallons of Distilled Water, pour them into the biggest pot you've got, put some of your MF's into the pot and bring to a slow boil for 10 to 15 minutes. There will be a film that rises to the top of the water which you should skim off often. This will be all the impurities that are trapped in the fibers of your MF's that are found in your regular tap water. Drain the water out of the pot to get all the impurities out of the pot before the towels come out. Then hang the towels to dry. Once dry, whip/snap/crack the MF's - then go dry your sled.
Bet they'll absorb water just the way you expected them to!
There are several thread on this topic and some very helpful members have posted entire water purification system pictures they've installed for their washing machines just because this is so common. I live in Jersey, so we share the same water supply/reservoirs - and I've got 3 different filters running to clean the water before we drink or wash with it - additional in-line filters for the washing machine and dishwasher too. (Only guy in the neighborhood with crystal clear glassware straight out of the dishwasher without a wipe down). My girl is amazed at how soft our clothes and bath-towels are since the system was put in. Changes everything, including the taste of the water!
Good Luck - and I hope this helps.