MMO states 4oz per every 10 gallons. I'm wondering if that formula is for how much gas your tank holds or how much gas you put in it? For example, 2 days ago I put some MMO in my Grand Caravan. My tank holds 20 gallons and so I put in 8 oz even though my tank was at about a quarter and so I only put in about 14 gallons. It did seem smoother but when I went on the highway I noticed an immediate drop in my mileage (usually it'll reach 23 or 24 mpg but it was at 21). Is this normal? Did I put in too much?