Some exhausts systems make it harder to get the 3/8 allen wrench in dipstick. I had to cut the short bent end of my allen wrench off quite a bit to get it to miss the exhaust pipe. I left just enough past the bend to get in to seat into the dipstick.
Also when a real bend for an allen wrench, and if what ever you are loosening is not too tight, you can make one easily. For a 3/8" you would need a 1/4" and two 1/4" nuts. These pieces of 1/4" hardware have 3/8" wrench size heads. You can thread the two nuts on the end of the bolt and tighten (lock) the two nuts together. Then put the head of the bolt into the diptstick (or whatever you need to loosen) and put your open end wrench on the nut closest to the bolt head, and back it out (the second nut will keep the one you are wrenching from just spinning on the bolt threads.
This can be done for many allen wrench sizes when you are in a bind and don't have the right size. Works well for larger allen wrench sizes pretty well. If you need more torque, you can use grade 8 nuts and bolts.