I run my car on Gasahol 95 and usually fill up at one of two filling sations (one near home, the other near the office).

I always fill up from near empty to a full tank.

Of course I occasional fill up other places and it is in some of the other places that I have noticed a marked drop in engine performance.

I strongly suspect some (from my experience quite a few) filling stations are selling 91 as 95.

To test my suspicions I a tried a ran my tank until nearly empty and then topped up with a quater tank of gasohol 91. The engine performance dropped to exactly the performance I had noted and which had raised my suspicions.

And no I don't wind up buying 91 as a result of some imagined lack of ability to speak Thai!

and you have just woken up to this scam , it happens in many gas stations , even with LPG i have been caught before too .

I always run my motorbike on 95 gasohol, but the other day I was at a station that only had 95 benzine. I was absolutely amazed at how much better my bike performed with the benzine. I chalked it up to it being gasohol, but now you've got me thinking.

Someone should buy a container of it and have it tested

I would suspect there may be some mixing of cheaper fuel with the better performance/priced fuel by some of those who are in on the profit picture. I have never noticed a fuel tanker unloading fuel at a service station during the daytime. Thus I have had my thoughts on this for some time.

fuels have been color coded for several years in the real world, for visual verification of the fuel being pumped. An example is diesel fuel, 3 colors, for non road use (tax free), normal operating temperture and sub zero operating temperture.