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BMW recommends Shell like it used to recommend Castrol. Shell bid more for the contract to be BMW’s oil supplier. It is not that BMW engines are made for Shell fluids. But Shell does make good fluids, including gasoline. I would not say any one top tier fuel is better than another. I would say any top tier fuel is likely better than most non top tier fuels.
I have put only top tier fuels in my BMWs and Porsche and have never had an injector or fuel pump problem other than on a 2008 E61 535xi with N54 direct injection engine that was known for defective HPFP and injectors in its early days — no fuel issues with that car in the past 15 years other than carbon buildup in the intake ports that I walnut blasted and scraped away and probably should clean again.
The biggest problem with DI engines is carbon buildup in the intake ports, which occurs even with top tier gas. You can dump as much Techron as you want in the tank and it won’t stop the carbon buildup because it is injected directly into the combustion chamber and never passes through the intake ports. A minuscule amount ends up getting past the rings into the crankcase and is vented through the crankcase vent system back into the intake but it is not enough to make any difference. It is the oil within that crankcase vent that causes the carbon buildup. Fuel dilution of the oil is probably 1-2%; with 16 ounces of Techron in 2500 ounces of gas, there is not much Techron getting into the crankcase vent and Techron is designed to do its thing as a liquid under pressure, not as a gas.
There are solvents that may help clean the intake ports and valves, but they have to be sucked into the intake by engine vacuum. The usual companies make them. Some are better than others. Most do not spray long enough to do much, so using 2 bottles like the Redline S1 kit has may be best.
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