Changed the oil in my 2003 S10 crew cab today, with mobile one synthetic. The 4.3 oil cap. is 4.5 qts. and I was thinking the jug I had was 4 quarts, it was 5 qts putting it 1/2 qt over. Yes, every manual says don't over fill but I've read that on most engines you can go a quart over with no problem. I don't see how a half quart could possibly cause a foaming problem. Anyone else do this and just leave it in?