I quite agree with you. I have got a car that returns 8mpg better while towing and about 15Mpg better solo, and also for comuting I use a small 1100cc car that gets near to 60mpg.I have sympathy for the proposed idea of boycotting a particular fuel supplier, but please spare a thought for the forecourt operator, and the longer term effects of such a unilateral move.
It is my understanding that many of the fuel retailers are independent companies who franchise the corporate image of the bulk suppliers.
If you were to ask any of them what profit margin the retailer gets, they may laugh at you. There have been some reports that that the margin per litre is in the order of 5p or less, and where a credit or debit card is used the margin falls in some cases to zero. Look at the number of independents that have closed over the last 5 years.
The bulk of profit comes from ancillary services such as sweets and news papers; the fuel is in many cases a loss leader.
There is now much greater profit in the value of land site, especially where it falls within an existing residential area. Modern building will get between 4 to 6 houses on a typical filling station site. At today's prices that's a profit after building costs of between .5 to 2 Million depending on area!
I suspect the effect of boycotting a particular supplier will cause redundancies, the sale of sites to developers. The target companies will offset their losses by increasing prices to bulk purchasers such as the supermarkets. With the loss of the independents the competition will be diminished and guess what, there will be less pressure on the supermarkets to keep prices down.
My view is that the only way to force prices down is for the consumer to use less.
I don't want to put any small businessman out of business, I know first hand what that feels like.
But lobbying MP's gets nowhere. Ears flap only at selective good press and self promotional subjects.