Q: i put 91 super in my car and is says use 87 premium now my battery light is on. what is going on? 2009 Kia Sportage

asked by on March 19, 2017

I put 20$ worth of super 91 fuel in my vehicle before i realized it was super. I had a quarter tank of regular 87 gas in it from before. This is what my car calls for. After i realized it i paid for the gas and started my car and now the battery light is on. The owners manual says using plus fuel can really mess up my car and transmission. What did i do to my car?

My car has 170000 miles.
My car has an automatic transmission.

Hello - you did nothing harmful. Your car may have a small level of performance improvement for this tank of fuel, but nothing extraordinary. Long term use of fuel with a higher octane level, MAY lead to increased levels of unburned additives in the exhaust and catalytic converter, but we’re talking about 10s of thousands of miles here for any "damage". The engine simply burns the premium fuel as-is, and doesn’t really use the additional anti-knock additives in the fuel. No harm, no foul. The battery light may be a slipping or broken serpentine belt, a failing alternator, or voltage regulator. I recommend a charging system inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.

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