Re: 'Pit Stop' I am amazed that, if HJ's statement about the fuel usage is true, why manufacturers of non-high performance cars would expect owners to use high octane fuels from branded filling stations which also have lots of extra engine/exhaust cleaning additives in them to remain relaible over the longer term. After all, Japanese cars (up until Nissan joined up with Renault) never had such problems and are specifically designed to run fine on lower octane fuel (I believe one 'grade' below our standard RON95) which is mainly available in poorer countries. My own (albeit limited) experience owning two Japanese petrol-engined cars for a long time (8 and 13.5 [and counting] years respectively) has shown no engine issues at all, backed up by many other Backroomers who have owned and run such cars over the years. I'm wondering if the defining factors are that the more modern cars that seem to have issues are both direct injection and small capacity turbocharged, which mine were not. More complexity generally means they need to be treated more sympathetically or expect parts not to last as long and cost more to replace? The same goes for those makes whose engine designs deliberately use engine oil to reduce friction in the cylinders thus and gain mpg by allowing for some mixing of the fuel and oil, whereas the older engine designs like my cars', both of which used very little oil at all, not once needing a top-up between services.

If you are actually an "engineer", then why are you surprised?. Maybe a domestic appliance "engineer"?.

HJ adduces no evidence for that last sentence - don't overreact Andy, it's one of his hobby-horses.

In my experience many cars run better on higher octane fuel and not just the sportier ones. I believe it is because their ECUs are calibrated to allow for this fuel so the manufacturer can then get better pollution figures in government tests. Our automatic 1.6 Nissan Note likes 98 octane fuel (preferably VPower) and changes up gears earlier due to the improved torque and accelerates better as well. Add to that the increased MPG and the extra cost is easily justified. Of course the car goes on 95 octane but the lower performance and MPG is noticeable.

Given the price of (for example) Shell v-Power is currently about 10-15% more than supermarket Ron95, somewhow I doubt if a standard car will achieve an mpg boost of the same. Note that it doesn't boost mpg AND power/torque at the same time, just one or the other.

Even in sports cars, the effect, whilst noticeable, is not huge, and certainly not the min. 10% which would make the higher price justified. For sports cars that are supposed to run on super, then the higher stress on the engine and better performance is what such fuels are used for.

Yes, the extra cleaning agents help clean dirty/gummed up engines, but often that's due to either poor engine design, not well maintained and/or the car being driven unsympathetically, including mainly for short trips from cold (lots of unburnt fuel), or being thrashed when not warmed up. Hence my comment about Japanese cars being designed to cope better with lower octane fuels and being abused.

Ordinary cars should have no problems with standard Ron95 if they are designed properly and looked after - and why so many older cars on the road these days are Japanese.

You might find that your main mpg 'boost' is only because the V-Power cleans the injectors and valves if you car is/has been mainly used for short trips from cold. Once cleaned up, the difference between super and regular unleaded will probably be much less than before (clean engine). This is why I recommend using a decent fuel additive (injector cleaner) every now and then instead for ordinary cars - it's just as effective and about 1/3 - 1/4 of the price difference of branded super fuels.