I also own a 1.6L GDI 2012 Accent.
I only put 87 octane gas. My MPGs have been great and on the money considering I drive 40/60 city/hwy and I average 34-37mpg depending on driving style.
I have also put in many different types of oil since I've owned it, which, by the way, I'm nearing 27,000 miles on the odometer.
In the manual, Hyundai recommends Quaker State, which is cheap in terms of price.
Here's a list of oils I've had in my car so far. Note, that I have not done any UOAs, at least not yet.
-Factory fill
-Mobil Super
-Kendall conventional
-Kendal Liquid Titanium
-Quaker State green bottle
-Pennzoil (yellow bottle)
-Quaker State ultimate durability
-Castrol GTX (gold bottle)
I would suggest you give quaker state a try and see if you like it. I also suggest that if you are going to buy the green-bottle quaker state, then change it every 3000 miles. The gold colored quaker state synthetic is better, but I wouldn't go beyond 4,000 miles on it. I ahve noticed that when I had the green bottle QS, beginning around 2500 miles, the engine noise was slightly more noticeable and accelerating felt harsher rather than the smooth acceleration you get from fresh oil. Using the quaker state gold bottle did not generate this noise during the tail end of the OCI, and neither did using the pennzoil yellow bottle. But this is all anecdotal.
So as far as oil goes, I'd recommend a high quality conventional, such as pennzoil, or synthetic. I'm liking my castrol gtx. No noise whatsoever and I'm nearing my 3k interval. I'm still changing it within the limit so that if any warranty issue crops up, my service intervals aren't called into question. Oh and BUY HYUNDAI OEM FILTERS. These engines are finicky and the OEM filters are top notch filters.
As for "rich burn", well there have been ECU updated for our 1.6L GDI engines where fuel ratio has been modified slightly.
I would take it to the dealership to see if there are any updates for your car.
You also do not need to use fuel system cleaner if you are putting in top-tier gas, such as Chevron, BP, Shell, etc. which have fuel detergents that prevent carbon build-up, which is very detrimental for GDI engines.
Carbon build-up is much more noticeable in our GDI engines as your MPGs will suffer.
Originally Posted By: TheOtherGoose
Yes - Hyundai does not require premium fuel for their normally-aspirated 1.6L GDI engine. It does have a somewhat higher compression, though (11.0:1, if I remember correctly) - could this be another reason for running rich?
GDI allows for high compression, hence GDI is almost like a diesel engine. The high compression actually allows for less fuel to be used.
Short trips are also detrimental since the lower temp of the engine does not help dissipate fuel dilution in the oil, so try and drive the car up to normal operating temps. This will help keep the oil in the engine last as long as it needs to be.
