For Prime members only, Amazon offers the Shell Rotella T6 5W-40 Synthetic Diesel Motor Oil 1-Gallon Jug, model no. 550019921, for $11.29 with free shipping via the steps below. That's $2 under our mention from October and the best price we've seen. (It's a current low by $8.) Deal ends April 30. To get this deal:

1. View the Shell Rotella T6 5W-40 Synthetic Diesel Motor Oil 1-Gallon Jug for $19.16
2. checkout via Subscribe & Save to cut that to $16.29
3. redeem this $5 mail-in rebate for a final price of $11.29