What Kind of Fuel? Regular or Premium

[HPIA4v2]

If no premium was available, not much you can do.
short of adding Xylene or Toulene (from home-depot paint dept) to get that octane


Honestly, the idea of running regular unleaded to save money is not new... BUT do this please.
record your mileage for a month running premium then the next month on regular (maybe two months if you really want to be fair). Then comeback here with the result.

Since we all agree(this is a must unless you can prove otherwise), that to prevent knocking due to turbo (high-compression engine) and nature of BMW engine running hot to save fuel already, using regular will retard engine timing as we all know it means less piston travel thus less power. In any real world to get the same power point you need to burn more gas, so at the end mileage suffers.

Let see, X6 on average gets you 17mpg, the saving between regular to preimum is 20c/gallon (let say $3.4 vs $3.6) or 20c/360c * 100 % or ~ 5.5%

now let say you loose 1mpg, 1/17 * 100% ~ 5.8%

Do you really save money at the end??? while still risking knocking if that knock sensor momentarily (in hot summer day, with some carbon build up in the engine etc) late to retard timing???

BTW, this has been discussed in BMW forums to death, I have so many people told me how they loose mileage even on 530i, 330i switching to regular; and those are non-turbo engine.

You probably save money by making sure, air-filter, spark-plugs and tire pressure are good; but if you incline to put regular on modern BMW engine, no one will stop you.
Yes, putting regular in BMW is fine but does make sense?

[vadim_s]

You guys beat this horse to death, however, my 2013 X6 (US model) says 89 minimum on the fuel tank cap. Is 89 considered Premium?

Aha, found the answer in the manual:

Recommended fuel quality: BMW recommends AKI 91.
Minimum fuel grade: BMW recommends AKI 89.
Minimum fuel grade: Do not fill up with fuel below the speci‐ fied minimum quality; otherwise, the engine may not run properly. If you use gasoline with this minimum AKI Rat‐ ing, the engine may produce knocking sounds when starting at high outside temperatures. This has no effect on the engine life.

Therefore, this answers it for others looking for the same information. _91_ or higher is what is recommended. 89 is minimum, but could cause a knock.