Back in 2000 I bought a focus turbo diesel. My commute was 60 miles each way, mainly M4 in West Wales, Llanelli to Cardiff. A no-brainer at that mileage. I experimented with Miller diesel octane boost. From memory. £12 a bottle for multi dosing. Car ran fine, no noticable power increase ( I couldn’t feel on3).. When on bottle 2 I started mpg checks as bottle 1 primed the system. My mpg increased. I converted it to money value. Bottle cost £12, fuel saved over the period of bottle use £36. Net saving £24. The time per bottle was 2-3 months ( can’t remember which. A decent saving. A mate tried it in his car but no difference found. It was a Golf diesel so, in hindsight perhaps not a good comparison!
Plus 8 observations next. I had occasional MIL light come on. Fault was “ random intermittent misfire”. Car was running well with no discernible misfire. GEMS system and it does a stats check and requires a triggering for a fault at a predetermined detection level. I checked everything plygs, leads, connections, new filter ) but it still occasinally popped up. Fuel was not getting stale due to regular use. I tried V-Piwer. Bingo! No fault codes. I reverted to 95 octane and they restarted. So 97 it is as much as possible with 95 as a back up.
MOT history for the Plus8 showed lambda results just coming in ok towards top limit from previous owner historic files. Never had a fail since I owned the car. Last Nov MOT with V-Power with 5% ethanol gave the lowest lambda reading I have noted. Ethanol effect?
My next obs will be with Esso zero ethanol if I can get it easily. V-Power pre MOT though, you never know!
I have looked for data about ethanol effect on lambda in emissions tests but not found a good reliable source yet.