Credit Cards with Fuel Rebates

With soaring fuel prices, I am looking into ways of cutting down fuel expenses.  I have been light on the accelarator pedals, coasting on the roads and scheduling my trips and routes. I also looked into these credit cards with fuel rebates ie BPI Petron-Mastercard and Citibank Shell Visa. 
I prepared a sheet to see  whether one can  really have fuel savings using these cards.

Credit Card	BPI Petron Mastercard	Citi Shell Visa Card
Fuel Rebate	3%	5%
Annual Fee	1,550	1,800
Fuel per year in Peso to be charged to credit to be able to save on Fuel	51,667	36,000
Fuel per month in Peso to be charged to credit to be able to save on Fuel	4,306	3,000
Savings per month if fuel per month is at 5000pesos	21	100
Savings per month if fuel per month is at 6000pesos	51	150
Savings per month if fuel per month is at 10000pesos	171	350

Here are my findings:

1. You have higher rebates with Citibank Shell Visa however the annual fee is higher thank BPI Petron Mastercard
2. You have to pay annual fees which reduces your "fuel cost savings".
3. For you to be able to realize savings on fuel cost/rebates, your fuel expenses charged to your credit card should be more than 5,000pesos.  Also you should have full payment every month on your credit card to avoid charges.

If you are going to use these credit cards for the fuel rebates and your fuel expense is not above 5000pesos, you are better off using your regular credit card or cash payment.