My Plus8 was always close to the lambda upper limit on MOT tests. I used V-Power petrol regularly. One year I had been using E10 for a few fill-ups as no no E5 available, up to MOT time. That test came out lower for lambda. I am wondering if the extra ethanol helped. E5/ E10 were stated as “up to” content so no guarantee of how much at any one time so not the best assumption on effect.
My mate took the cars for MOT as he was a tester. He advised trying Cataclean but no guarantee of effect. Another mate also suggested petrol from the big companies not small outlets/supermarkets as the market was based on cost of supply and additives cut back on to sell to these outlets for cost reduction. He was in international vehicle recovery ( including a lot of police work) and his contacts told him about the additives situation.
