There is no problem doing that, but I don't think it will do any good. I think you would be better off using M1 10w-30 in the summer and 0w/5w-30 in the winter with 5k> drains. Mobil has a 0w-20 that you could run in the winter months. I think this would be a good idea. Mixing is fine, but in your case you would end up with approximately a 3.5w-30 so it's not worth it. Realize you don't know which viscosity you are getting when mixing, only an approximation.
[ May 17, 2003, 09:38 AM: Message edited by: buster ]
I agree with Buster. Very little difference between the 0W and 5W. It really only becomes more important inthe events you need an extremely low pour point as in the dead of winter. I would go even further and say you could even use the 10W all year around. I use nothing but the 10W. Absolutely no problem with it even down to -17 F in our Pennsylvania Winter.
I do not own a Ford but it seems like little would be gained from mixing the two. I also doubt that anything below 10W30 in a synthetic is really needed unless you live near in near artic like counditions. The Mobil-1 10W30 has the best overal track record of recording good UOA results out of their entire product line in the U.S. It will pump and flow to some insanely low temps compared to what most people actualy see.