I searched and didn't find too much on it. Whats the difference between the SR-1 and the SR-5? I currantly have 6 qts ($75.00!)worth of the 5w-30 SR-5 stuff in my 4.0 Jeep. The shop only carries SR-5 5w-30 and 20w-50. Waddaya's think about sampling it @ 4000 miles for starters?