Fuel Changes Set Off Warning Light Hell!

A 1,500 mile road trip to see the Great American Eclipse was just completed, and it was well worth every mile. While my attempt to record the event fell far short, the trip remains a big one crossed off my personal bucket list.

Low Fuel IndicatorThe car, an Audi A4 2.0, enjoyed the trip too, but evidently not the fuel it had to deal with. In chronological order, here are the notable ‘milestones’.


  1. The car hit 34.2 mpg on the return trip. In my 75,000 miles of ownership, it has only ever tickled 32 mpg.
  2. EPC Indicator SymbolShortly after returning, the EPC (Electronic Power Control) warning light came on (I used the Dashboard Symbols app for this one!). Power was reduced and the CVT (Continuously Variable Transmission) began behaving like a traditional automatic. Pulling over and restarting the car resolved the light and power was restored.
  3. Check Engine Light SymbolTwo days later, the EPC light returned, this time accompanied by the Check Engine Light. A restart resolved the EPC light again, but the check engine light remained.
  4. Using a code reader, I discovered three emissions codes and the power control code. I cleared them all as a test because of what follows.

Experience, along with the added fuel economy, suggested that I had come across a variation or two in fuel formulation. In fact, a little research showed that there are no less than 18 different gasoline formulas in use in the US! This does not consider additives such as detergents that higher quality suppliers use in their gasoline, which takes this story back to experience.

I had twice previously encountered check engine lights that I was able to trace to the use of a name brand fuel that did not appear on a list of those using detergent and other additives. Sticking to higher quality fuels had until this trip kept the engine light in ‘check’. A few days of driving on my ‘normal’ gasoline was all it took to return the engine to smooth operation.

Coincidently, the car’s emissions test was due, and it passed.

The upshot is, don’t assume a serious engine problem when a check engine light comes on. There are too many variables in the fuel supply. Stick to those on this list. One of the major auto parts stores can be a useful ally. If the codes are emissions-related, they can clear them for you while you test a better fuel.

Note as well that if the light suggests an issue with something electrical, a restart can often times reset the system in question. It never hurts to try.

Overall, remember that a quality fuel, even if it costs a bit more, can be well worth the added expense.

Above all, happy motoring.



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