[i30autoju]

Hi all, my wife's new i30 petrol is now due for its first 1500k service.  No problems showing.   It has always had 91 ulp in it since new , but I decided to run a tank full of Premium (98) in it to see what happened.

It does mostly highway use and started off (new) giving 6.5 L/100 and soon settled on giving around 5.7  Lt/100 doing same work.  After  I put the tank of Premium in (and reset the computer) it still stayed on around 5.7 Lt/100.  I thought I should see better fuel economy using the 98?

Is there something I do not understand about this test, or maybe the computer isn't very accurate?

[mjt57]

My i30 is the first diesel that I've owned. So, all previous cars were petrol.

If the manual says "91 RON or higher" it's been my experience that all that happens if "higher" is used that you get a "higher" fuel bill.

I tried it in a Mazda Tribute, 2 Commodore SSes (Gen III and 5.0l V8s). And in my motorcycles (Honda CBR1000F and CBR1100XX and a Kawasaki ZZR1100).

With the ZZR if I ran 91 in it the bike would ping. So I ran leaded fuel (PULP wasn't widely available at the time.) But when I ran PULP in it, the rattling or pinging would stop, but neither performance nor economy changed.

Some of the lads whose bikes require 95 or higher have had to fill with 91 in some of the more out-of-the-way places. But they didn't really see much difference, either. Perhaps long term maintenance issues may crop up.

So, personally, unless the manual requires higher than 91, my view is to stick with standard ULP (and give that ethanol shit a wide berth...)

[FatBoy]

You might find it takes the ECU a couple of tanks to "get used to" the PULP.  It would have tuned itself to the 91 RON.

When I had a V8 Commodore (5.7l LS1 engine) we always ran it on 98 RON from Caltex.  We did notice that if we went back to 91 RON the car ran a little worse (not as much response) until we got it back onto PULP.

We also ran our old Corolla on PULP to stop the "pinging".  That Corolla had a 1.6l normally aspirated (carburettor) engine.

[Just Rick]

Like Gonz I have found the same results,on 91 Ron and 98 Ron in my commodore was in fact quiet a difference,I have also found in the diesel there IS a  difference in the use of truck Deisel (normal) and Vortex/Ultimate Diesel (higher Grade) I for one have absolutely NO CONFIDENCE in the trip computers in these cars,as I have found on so many occasions that the manual calculation of fuel usage to mileage,is so different to the computer,my view is the trip computers in these cars are very cheap basic units and not very reliable OMO

[i30autoju]

Thanks for that advice all - This car doesn't ping under load on 91, so that's a good thing. I'll keep using the 98 and see if anything changes, but I'm thinking maybe a inaccurate computer?  But, maybe it will change in time.?

[Asterix]

I tried that exercise with my previous car, Nissan Primera 2,0 petrol, and my current i30 Diesel, when towing the caravan through Germany.

Neither in the petrol or the diesel could I feel any improvement in the performance or consumption, but my wallet felt hurt..

[pidim]

I also don't notice any difference in 91, 95, 98 on fuel economy on my 1.8L petrol

[rustynutz]

I for one have absolutely NO CONFIDENCE in the trip computers in these cars,as I have found on so many occasions that the manual calculation of fuel usage to mileage,is so different to the computer,my view is the trip computers in these cars are very cheap basic units and not very reliable OMO

You've mentioned that before, Rick...
I think most comments back then were that the trip computer is quite accurate for everyone else (within a few points)....so not sure why yours is so bad.... 

[kyle0968]

From new, I have now filled up the car 28 times and I have been logging each in Fuelly app. the 4 most recent fillups were on 91 octane, while most of the fillups before that were on 98 octane where possible, with several times doing 95

Although all 4 recent fillups were well over 9 liters/100kms, At this stage it does not deviate convincingly from previous fillup data. will probably need more fillups to establish a credible pattern.   
 

[John B]

While we are on the subject of the correct octane to use and as I have not taken delivery of my car yet  please excuse my ignorance on this subject, is it Hyundai's  recommendation to use 95 octane and if so would there be any problems with the warranty if  91 octane was used and a problem occurred with the engine. There seems to be a bit of controversy over what octane fuel to use. Some people seem to favour the 95  for its cleaning agents even though performance  wise they say it has made no difference  but it is more expensive, so if a person was contemplating keeping the car for many years would it pay to use 95 rather than 91 and has there been any evidence  of any problems from using 91 octane. One last question why has 91 been discontinued in Europe ?

[rustynutz]

With the FD, Hyundai do state that 91 octane is ok....but, some have found their i30's will ping on it.
As our petrol is a lower octane than in Europe, most European cars will run better on 95... 

[rustynutz]

If I remember correctly, when our Government introduced unleaded back in the 80's they, in their infinate wisdom decided 91 octane was the go although pretty much everywhere else used 95....

Ya gotta love the Aussie Government..... 

[Phil №❶]

If the handbook says 91, then 91 should do, after all, you're following their recommendation.

With petrol engines, I ALWAYS use an upper cylinder lubricant Redex, or similar. Petrol is a solvent and tends to inhibit the protection of oil in the valve train area, especially the valve seats. Just my preference FWIW.

[John B]

If the handbook says 91, then 91 should do, after all, you're following their recommendation.

With petrol engines, I ALWAYS use an upper cylinder lubricant Redex, or similar. Petrol is a solvent and tends to inhibit the protection of oil in the valve train area, especially the valve seats. Just my preference FWIW.

Thanks Phil, when I get my handbook I will have a study and follow that.

[Phil №❶]

This is page 7 of the handbook, have a gander.

GD Fuel - Google Drive

[John B]

Thank you Phil, very interesting ,I can se were there are the differences of opinions now, looks like personal choice .

[Asterix]

Here we still have 92 & 95 octane. 98 is very rare. Shell V-power and the alike is ridicules expensive.

As the price difference between 92 & 95 is less than 0,01 AUD I've always used 95 on all my petrol cars.

[John B]

If the handbook says 91, then 91 should do, after all, you're following their recommendation.

With petrol engines, I ALWAYS use an upper cylinder lubricant Redex, or similar. Petrol is a solvent and tends to inhibit the protection of oil in the valve train area, especially the valve seats. Just my preference FWIW.

Thanks Phil, when I get my handbook I will have a study and follow that.

Just to clarify, some of you know I am waiting delivery of my new car but my daughter already has hers and maybe you are wondering why I have not read her manual, well the truth is I am like a big kid and did not want to spoil the enjoyment of getting the car and sitting down and studying the manual at the same time, silly I know but being over 70 yrs old I still love it when a plan comes together. 

[Geothe50]

I for one have absolutely NO CONFIDENCE in the trip computers in these cars,as I have found on so many occasions that the manual calculation of fuel usage to mileage,is so different to the computer,my view is the trip computers in these cars are very cheap basic units and not very reliable OMO

You've mentioned that before, Rick...
I think most comments back then were that the trip computer is quite accurate for everyone else (within a few points)....so not sure why yours is so bad.... 

Rusty, my own experience after 19 refills is a standard deviation of 0.64L (!) between trip meter average and real average L/100km. The closest was 0.11L - worst case 1.32L difference. I think the trip meter is a useless gimmick.

[rustynutz]

Thanks for that.... 

I reckon those figures aren't so bad....
And at least the trip computer isn't under reading...

Btw, how do you know if your filling of the tank was completely accurate? 

On my recent trip away I was topping the tank at the servo and then checking it back at the house I was staying at which wasn't far down the road and the fuel had disappeared out of sight.
This leads me to believe that filling right up until it's about to spill out is not necessarily as accurate as we may think....