OK, I've been wondering about these questions for a while, & the posts in my last question beg me to finally ask: 1) What percentage of fuel creates x change in viscosity? 2) At what percentage value can you first detect any viscosity change? 3) At what point does fuel contamination negatively affect engine oil lubricity? 4) What percentage value is so great that you wouldn't want to use the oil any longer? 5) Can viscosity actually increase by way of fuel contamination?