My Hyundai GDI 2.4L non- turbo engine has a 11.3.1 compression ratio . Not sure if this is considered high compression or not and if such an engine benefits from or needs high octane gas ? The owners manual just states 87 octane minimum .
Use Only High Octane Gas in High Compression Engine ?
- Thread starter ChrisD46
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Unless it explicitly states to use high octane, I've never been able to show a statistically significant difference between regular and premium. This included dyno time, dozens of fuel ups of different grades driving the same routes and logging timing curves and spark advance and retard... The only difference was price.
If the owners manual has wording in it that says 91 reccomended then go ahead and use premium. But otherwise, in most cases, I believe it's extra money that could be better spent elsewhere.
If the owners manual has wording in it that says 91 reccomended then go ahead and use premium. But otherwise, in most cases, I believe it's extra money that could be better spent elsewhere.
You'll see no benefits in higher octane just purchase Top tier fuel.
There won't be any knock benefit since your engine's control system can detect incipient knock and adjust spark timing. Whether there's any MPG benefit, I've yet to see lab tests that control all the variables to show that there is.
However, there's definitely a cleaning benefit to using higher grades from brand name stations (Shell & ExxonMobil at the least) since they have an appreciable amount more additives. Notice I said grades and not octane, since again the octane isn't helping clean the engine/fuelsys, the additives are.
Several BITOG members use higher grades for the cleaning benefit, including I with a similar compression nat aspirated engine.
TLDR: use Top-Tier 87.
However, there's definitely a cleaning benefit to using higher grades from brand name stations (Shell & ExxonMobil at the least) since they have an appreciable amount more additives. Notice I said grades and not octane, since again the octane isn't helping clean the engine/fuelsys, the additives are.
Several BITOG members use higher grades for the cleaning benefit, including I with a similar compression nat aspirated engine.
TLDR: use Top-Tier 87.
If lower octane fuel can cause an engine to retard the spark to avoid knocking, is it not reasonable to assume that a higher octane fuel will let an engine management system advance its timing.....perhaps to a degree which improves performance?
Just asking.
In the case of the original poster’s case, higher octane won’t improve anything. His engine management system won’t advance timing, cam timing events (variable valve timing), or fuel enrichment. It’s only designed and programmed for 87 octane. However on an engine that is designed and explicitly calls for higher octane the engine will retard timing etc. to handle the lower octane thus less than optimal efficiency and power.
Static compression doesn't mean what it did in the 1970's. You get (sometimes) more valve overlap and EGR that can lessen the effective compression ratio, as well as knock sensing and engine management to reduce the dangers of preignition. Direct injection cools things down, too.
This compression ratio seems like something you were blissfully unaware of, then suddenly read about, then became worried.
This compression ratio seems like something you were blissfully unaware of, then suddenly read about, then became worried.
Definitely something to consider, verses a Penny pincher, who will cross the street for the cheapest of the Cheap fuel.
Having said that to the op, i have naturally aspirated motor with 13:1 compression, while it says 87 minimum, I normally run midgrade.
Our Carnival has 12.3:1 compression. It runs fine on 87, but has noticeably more low-end torque on 93. It honestly drives way differently on high octane.
The manual states two different things. One section says 87 minimum required, another section recommends 91
The manual states two different things. One section says 87 minimum required, another section recommends 91
Your engines Horsepower/Torque ratings were probably using Premium Fuel. They've made it compatible with 87 to sell the cars but you won't be getting the full power. I do think about long term durability by not using Premium on a high compression engine but it's probably fine so long as you're not stomping on it at every chance. I do consider your 11 to be high.
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Brings back memories of old cars with "high" compression engines.
I had a 1968 Pontiac Catalina that required high octane fuel, I believe it was only around 11:1 compression.
If I cheaped out and used regular fuel - I would have to turn it off in Drive to get it to stop running. Otherwise it would diesel on forever.
Modern engines are designed to use what the manual tells you.
I had a 1968 Pontiac Catalina that required high octane fuel, I believe it was only around 11:1 compression.
If I cheaped out and used regular fuel - I would have to turn it off in Drive to get it to stop running. Otherwise it would diesel on forever.
Modern engines are designed to use what the manual tells you.
If it doesn't knock or ping then you are good with the lower octane fuels. I had two identical Geo Metros. A 1996 and a 1997. One of them pinged without premium fuel the other ran fine on 87.
I have a 2013 Kia that pinged terribly with 87 octane. Even set off a knock sensor code. Had to run premium for years until a discovered a TSB that said a software update might fix the problem. Paid dealer $200 for the update which fixed the problem.
Around here, premium is 25% more expensive than 87 octane so using it effectively reduces your fuel economy by 25%. That's a big cost over the life of a car. I calculated that paying that $200 for the software update would pay itself off in fuel savings in between 5000-10000 miles.
I have a 2013 Kia that pinged terribly with 87 octane. Even set off a knock sensor code. Had to run premium for years until a discovered a TSB that said a software update might fix the problem. Paid dealer $200 for the update which fixed the problem.
Around here, premium is 25% more expensive than 87 octane so using it effectively reduces your fuel economy by 25%. That's a big cost over the life of a car. I calculated that paying that $200 for the software update would pay itself off in fuel savings in between 5000-10000 miles.
I had a '68 Catalina too. That thing was a big old hoagie car. Drove like a boat. Had a lot of fun with the girls in that car back in high school. Used regular fuel.
Just use what you owners book says.....
My dad had one too...Took my driving test in that....The parrelell parking was a bit tricky....
For you young kids, "Regular" leaded was 89 octane.
I imagine Pontiac had a dozen different engine choices with different levels of tune.
One issue with GDI engines is, the "cleaning benefit" only applies to injector tips. Using fuel like Chevron with Techron will keep injector tips clean which IS an issue with DI engines, but does nothing for the backs of the intake valves.
MAC and SNAP-ON both make a tool setup that cleans the carbon off the valves. It's pretty cool, but labor-intensive. Pull the intake manifold back, position the vacuum snorkel next to the valve, and there's a device that looks similar to a airbrush gun that sprays crushed walnut shells onto the valves as the vacuum collects them.
This tool was originally intended for MINI Cooper engines, but now with Hynudai, Kia, GM and nearly everyone else using GDI it's finally making money for the shops that invested in them!!
At the very least, if you're getting knock with 87 and engine management is having to retard spark timing, you're losing performance. Running 93 eliminates knock and eliminates the need to back off spark timing. Sounds like you do indeed get better performance with higher octane.
The Mazda I just bought rates the engine at 227 horsepower on regular and 256 on premium.
Sorcery, I tell you. Someone just said it makes no difference!
The GM 6.2 I had (not the one I did extensive testing on, that is my daily with a 3.6) was a dog on 87. That said the manual states for best performance premium is reccomended. It was like a 3mpg difference on trips using 87 vs 91. Typically if it is calling for it, it will take advantage of it. Felt like a different truck after you put 91 in it and drove for a bit.
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