2012 Accent 1.6L GDI Engine Rattle/Knock/Buzz

[jamiem]

Originally Posted by 2012bostonredse

Higher octane gasoline doesn't increase mileage. In most cases it will decrease it.

That's true in most cases, but if the noise was engine knock mileage would definitely benefit from a higher octane. The engine isn't running optimally if detonation is occuring, the normal combustion process is being interupted and the timing is probably being retarded if the knock sensor is doing its job.

In short, the engine will run best on the lowest octane that doesn't cause detonation.

[oneir]

So far I have only run two brands of gasoline in my Accent, Shell and Chevron, plus whatever junk gas the car was filled up with at the dealer. Nobody can hear this pinging sound and judge its serverity but the OP, so it's kind of impossible for anyone to diagnose the problem and prescribe a fix. But I would say, as a non-mechanic, that different gas can make a noticeable difference with this engine. After the free tank of gas from the dealer was used up, I put in Shell and the improvement was unmistakably clear. The engine was smoother and quieter. I've used only Shell 87 and 89 octane since then, except for about a tank and a half of Chevron 87 octane. (I am saving all my gas receipts for possible warranty documentation purposes.) It seemed to me that the Shell was still better than the Chevron at producing a smooth and happy sounding engine, despite the Techron additive in the Chevron and even though both are considered top tier gas. So back to Shell. But I am very interested in other people's experiences with different brands of top tier gasolines.
I had originally been using Shell 89 octane, but switched to 87 and noticed no difference. My mother's car comes with a recommendation to use high octane gas, but you can use regular according to the manual. But the engine sounds very wheezy on regular gas. The Accent has an even higher compression ratio, yet it seems better able to adapt itself to 87 octane - at least so far as you can detect with your ears. Then again, it might be that brands of gas could matter as much as octane rating in quieting a knock. My mother's car more or less always gets BP gas which is not on the list of top tier suppliers, while mine gets Shell.

Anybody else have a favorite, trusted gas after trying different brands?

[2012bostonredse]

To keep it simple, just do what the manual says. 87 Octane Top Tier. With that being said, I see no difference in engine sound between the different Top Tier gasolines I've used. I usually goto Shell because its the closest to my house. Yes, occasionally I do hear "pinging" when the engine is under strain, such as going up a steep hill with the RPMs low. That is expected. I wouldn't spend extra money buying higher octane gas, even IF it helped with the pinging sound, because the manual says to use 87. A lot of people think the words "unleaded plus" or unleaded premium" implies an increase in quality. Not saying you guys on here fall for this, just saying that its a widely spread fallacy. Higher octane just means higher resistance to ignition, for engines designed for it. I just like to keep it simple, and use what the manual says to use.

[jamiem]

If it's only a very occasional and mild pinging I wouldn't worry about it either, as all car manufacturers regard that as normal, and like to remind us that today's engines are built tougher and are able to withstand some pinging. And that's true, but the fact remains that pinging will cause damage to the pistons and other internal parts of the engine and shorten it's life. How much damage is relative to how serve the pinging is, there's lots of information available on the topic for anyone interested:

wikipedia.org/wiki/Engine_knocking
autos.com/car-maintenance/what-causes-engine-pinging

I live in a small town in Canada and Esso is the only Top Tier brand close to me. While I have used other brands on occasion I've never noticed a difference but then again I've never looked closely to compare them, I'd always assumed the gas around here is all from the same supplier, and that the only difference is how much additives each station uses. I'm only guessing on this however, as some people will swear that some brands will give them better performance/mileage/etc. In a larger city or in the states I imagine thats it quite possible there could be a noticeable or measurable difference between brands.

[Tightwad]

A direct injection engine has a reduced tendency to detonate because of the decreased time fuel spends in the cylinder.

Direct Injection Engines are inherently noisier due to the extreme high pressure of the injection.