Nissan Patrol 4x4 (Africa)

We may be on to something here it looks like certain engines just run better with some fuel formulations.

Everybody uses the same base fuel from a local refinery but I understand each company adds their own additive package to the fuel when it goes into the delivery tanker truck.

For example my Merc loves Shell but the 540 hates it. This is quite understandable as the fuel companies have to formulate an "average" additive package for all cars and I think they all lean in one or another direction a bit due to marketing and the customer base they are trying to target. Just look at the advertising...

BP - Only ever adertise how clean their fuel is (Low additive package and low sulphur that won't dirty sensors?) I used to use only this with terrible mileage. Good for hi tech cars and probably closer to Euro III spec than the others.

Caltex with techron (target dirty engines with a heavy additive package?) My car doesn't seem to care but it helped my old 535i a few years back.

Shell ( Have always adertised a performance fuel, good burn additive package?) I definitly get a boost from this fuel especially if weather is hot. Mileage is average high rev power very good low rev power a bit flat.

Sasol (Used to often tout theirs as being a performance fuel, but not these days?) Car actually doesn't idle smooth with this.

Engen ( Advertise their unleaded as being "Dynamic" - maybe a balanced additive package?) My 540 goes super smooth with this and mileage increases, not more power but I can feel I'm pressing the acellerator less to maintain a set speed.

Now the thing with any engineering is you have to compromise - always you can't have a fuel burn perfectly AND clean perfectly AND leave the least deposits all at once, so you add more of one of the things it does, compromise on the rest and use it as an advertising stunt. You can have the cleanest burn for power but the fuel itself won't clean as well or you can have excellent detergent properties for cleaning and then it won't burn as well for power etc.

Diferent engine management systems and combustion chamber shapes will all prefer one or other of the formulations.

The only thing to do is try a few tanks of each till you find the one your exact car likes the most. With todays current insane fuel prices this could equal some significant savings, as it has in my case.

My particular car hates BP and loves Engen (the two extremes for it)

One more comment relevant to this. Modern engine management systems are typically designed to handle fuels from 87 to 100 ocatne and all they do when you throw a crappy fuel in is retard the timing and increase injector cycle for a richer mix that won't damage. throw a good fuel in and the adaptive EMS will try advance the timing and reduce injector cycle as far as it can go till it senses it's reached the limit of what the fuel allows.

Now to your average driver he would never know this is happening, the car would just feel a little flat and consumption would increase. So try the fuels and use the one that makes your car feel very responsive cruising on a light throttle (lean mix and advanced timing) because that is the fuel allowing the ECU to use the best settings. Only measure consumption 25Km after filling up with another brand and various driving conditions that allow the ECU to adapt.