[ejafus]

Hiya,

Twice now I've been in a situation where I've filled up my tank and then later in the day filled it up again, but only 3-4 litres (1 gallon). In those 2 cases, because it was only a few litres, I purchased the more expensive octane 94 fuel instead of the regular octane 87 fuel.

In both cases, two things happen:

1. Fuel range indicator does not update (it does if i put in regular fuel in a similar circumstance).

2. The car becomes sluggish when first putting my foot on the accelerator for about 100km/60mi. of driving.

Not sure what's happening here.

I know that the car expects 87 octane fuel however in every other car I've owned putting in 94 octane fuel boosts performance rather than hindering it.

 

[s.f.c.hooligan]

Mine is ignorant to supreme. It couldn't care less. No extra umpf. No extra mpg. Drives all the same. I don't bother with it anymore.

 

[Variant-K3]

The car is mapped for 89 oct . Unless th timing is changed and fuel remapped anything higher than 89 will do nothing . Well almost nothing , the fuel will not burn as well and you will get carbon build up rather quickly . Run what the manufacturer suggest

 

[honhon]

higher octane means a slower burn, so going up on octane doesnt really help a car...

performance cars use higher octane so they can stuff more air and fuel into the chamber prior to exploding.

i run 89 octane in my forte koup with the 1.6 turbo because turbo cars benefit from the later explosion, do to the turbo forcing air into the engine. even at a stock level trim.

honestly your wasting your money, it would be more beneficial to put in a can of seafoam or other cleaner to keep the engine clean rather than going up in octane.

more than likely what might be happening is the car is not able to change the timing enough to take advanatge of the higher octane.

also if the indicator isnt moving at all the tank sensor might not be high enough in the tank to sense that 1 gallon or so thats being added

 

[ejafus]

Understood... and quite frankly this car runs fantastic on 87 (which is standard 'regular' fuel in ontario and is manufacturer recommended), so you're all right -- not needed.

However in past compact cars designed for 87 octane I have fueled up exclusively w/91 at times or even for an extended period and never had any performance losses --- only gains -- designed for it or not.

W/the Forte, I get a VERY noticeable loss of power when accelerating from stop, to the point where from an outside observer, it may look like I have a standard transmission and have stalled.

Interestingly...that behaviour does not occur if the entire tank is using 94 octane...only if I top it up with a few litres overtop of a nearly full tank of regular 87 fuel.

Any ideas? I'd say I was imagining it but it's happen a few times now....and it does strike me as odd that the estimated fuel range does not change after me topping up the tank w/the 94 octane fuel... may not be related, but then, I don't know how the timing works.

 

[Hank Griffin]

87 octane is all you need for n/a 4cyl engines if you want to keep the pony's up put some fuel injector cleaner and engine cleaner in.

 

[Crimson]

I might be missing something when reading about this but I'm wondering if you were ever topping up a tank full of 94 octane with 94 again, or maybe 87 octane with 87, and experienced the same thing happening?

And how are you "topping" it up? Not a good idea to keep filling once the pump auto shut off occurs. The potential overflow can get into the emissions stuff via the filler neck and wreak havoc. Although I'm not sure if this is true of every contemporary vehicle with those systems, but I've heard about trouble from some anyhow.

 

[bgenesis12]

Regular unleaded Chevron gas always gets me more mpg than Shell. May not be a solid fact but for me it has proven true.

Love Chevron, hate it's price.. i still buy it OCCASIONALLY. Mainly on long trips.

 

[ZonaRob]

It's funny, but the information I've found on my GDI motor is that the Techron in Chevron gas is what the GDI engine needs to run properly over time.
It's my first GDI Kia, so I'm running Chevron 87 about every fourth tank, instead of buying the $5 bottle of Techron at Walmart.
Any ideas on other maintenance with the GDI?

 

[Ross]

I filled up with higher octane than usual yesterday, and now it feels really sluggish (2014 forte 5sx) I just recently got an exhaust put on and thought maybe that was why. But after readin this I'm thinking maybe the fuel I put in is why?!?

 

[Markus]

I'd be curious to know what would happen if the entire tank was filled with higher grade fuel. I'd like to think the ECU would learn and adapt to the "new" fuel, for example increase / decrease ignition timing. Depends on how smart the ECU is I guess. It does sound like it is, with only a small amount of higher grade fuel, not learning, maybe it needs an ECU reset to do that?
I am glad the car is set up to run on the lowest grade of fuel though, saves a few bucks that's for sure.

 

[ejafus]

New Behaviour

I put this in response to another issue "Full tank no gas, eh?" that another user posed, but it applies here too.
.....
Scenario 1: I have a nearly full tank (less than 100km/60mi driven) and decide to full the tank, but do so w/premium fuel (octane 94). Result: The gauge does not change to reflect the updated condition of the now full gas tank.

Scenario 2: I have nearly an empty tank (less than 50km/30mi before completely empty) and decide to add around 4 - 5 litres (around 1 gallon) of fuel -- this would bring me to about 100km/60 mi. remaining range) Result: The gauge does not change to reflect the updated condition by removing the low gas light nor does it begin to estimate remaining range.

In each case, turning the car off and on -- even for an hour so -- doesn't change the condition.
.....
I haven't done Scenario 1 for a long time now so I don't know if it is still having a perceived power loss so cannot update that point.

 

[FIN3SSED]

higher octane means a slower burn, so going up on octane doesnt really help a car... performance cars use higher octane so they can stuff more air and fuel into the chamber prior to exploding. i run 89 octane in my forte koup with the 1.6 turbo because turbo cars benefit from the later explosion, do to the turbo forcing air into the engine. even at a stock level trim. honestly your wasting your money, it would be more beneficial to put in a can of seafoam or other cleaner to keep the engine clean rather than going up in octane. more than likely what might be happening is the car is not able to change the timing enough to take advanatge of the higher octane. also if the indicator isnt moving at all the tank sensor might not be high enough in the tank to sense that 1 gallon or so thats being added

I think you need to do more research on a turbo car. Using lower octane on a turbo car is asking for trouble. Why do you think turbo cars and tuners opt for e85 instead of 94 Higher octane means better burn of fuel... Do research before giving false advice

 

[Acura_Kal]

Thank you for bumping an 8-year-old thread. I'll be closing it now.