91 OR 98 OCTANE IN CJ ES 2LTR N/A

peregrine

peregrine

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Had reason to believe ECU has two maps one for 91 octane and one for 98 octane. Had this confirmed by my Mitsubishi dealer service department who said 98 would give me a slightly better economy rate but weighed up against extra cost probable advantage would be debatable. I only cover a minimal amount of kilometers so cost is not an issue. Have decided to go 98, added advantages being superior product less chance of contaminated fuel plus additives etc: to keep things running cleaner with more refined fuel. Have no idea of increased power! Not particularly concerned but be nice to know.
 
Some more information to help with your decision:
98 has a shelf life of about 3 days. If you dont use it in this time, it goes "stale" and will lower its octane and will be moreorless the same as 91
91,98, and all other fuel types are kept in tanks next to each other underground. If theres water/other contamination in one, it can seep into the other.
 
I have a 2012 2.4L VRX (manual) and I owned a 2008 2L VRX (manual) and tried 91, 95 and 98!

I found 95 was the best for fuel economy, I have tried 98 too several times but didn't seem like it did any better than 91, if you want more km's per tank I would use 95, however 95 isn't available at all servos! I just use 91 nearly all the time as it is cheaper and easier for me to find in my area as every servo has it not just like 95 where it is only available at one servo (Caltex) in my area! 95 seemed to give me a slight power increase but nothing to rave about and the car ran a little better, the extra km's wasn't a great deal when you weigh up the price difference of 91 and 95, but 98 is a waste of time I have found in a NA Lancer!
 
donki said:
Some more information to help with your decision:
98 has a shelf life of about 3 days. If you dont use it in this time, it goes "stale" and will lower its octane and will be moreorless the same as 91
91,98, and all other fuel types are kept in tanks next to each other underground. If theres water/other contamination in one, it can seep into the other.
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Shelf life of 3 days? That can't be right! If it is right then there would be a heap of blown turbos as they in general require 98 octain and 91 octain is a no! no!
 
VRX_08 said:
I have a 2012 2.4L VRX (manual) and I owned a 2008 2L VRX (manual) and tried 91, 95 and 98!

I found 95 was the best for fuel economy, I have tried 98 too several times but didn't seem like it did any better than 91, if you want more km's per tank I would use 95, however 95 isn't available at all servos! I just use 91 nearly all the time as it is cheaper and easier for me to find in my area as every servo has it not just like 95 where it is only available at one servo (Caltex) in my area! 95 seemed to give me a slight power increase but nothing to rave about and the car ran a little better, the extra km's wasn't a great deal when you weigh up the price difference of 91 and 95, but 98 is a waste of time I have found in a NA Lancer!
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I will be sticking to 98 all the same. To each his own.
 
I am not sure if cars have separate maps as such for different RON rating fuels, however most (if not all) modern cars have knock sensors which allows the ECU to adjust timing etc depending on when it hears knock.
With lower octane fuel this knock will appear sooner and hence the ECU will compensate for it, generally meaning lower power output etc.

The higher end fuels (ie, 98) have additional additives though to keep things cleaner etc. I use Shell exclusively personally, as I do their oils.
 
Spetz said:
I am not sure if cars have separate maps as such for different RON rating fuels, however most (if not all) modern cars have knock sensors which allows the ECU to adjust timing etc depending on when it hears knock.
With lower octane fuel this knock will appear sooner and hence the ECU will compensate for it, generally meaning lower power output etc.

The higher end fuels (ie, 98) have additional additives though to keep things cleaner etc. I use Shell exclusively personally, as I do their oils.
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Thanks Spetz, all your point are spot on, I have had confirmation from two valid sources that my CJ MY15 Es has two maps. They say cleanliness only comes second to godliness? One big factor apparently worth doing is to decide 91, 95, 98 and stick to it chopping and changing wont only confuse you but could also confuse (oops wrong word) the ECU.
 
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peregrine said:
Shelf life of 3 days? That can't be right! If it is right then there would be a heap of blown turbos as they in general require 98 octain and 91 octain is a no! no!
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Blown engines but thats nitpicking.

An engine will run on 91, it will even run on diesel for a couple kilometres before conking out. Most cars that mandate 98+ fuel are able to detect if the octane is lower and either add more fuel and/or pull timing to adjust until the next tank.
I go through a tank of 98 every 4-5 days on a very high compression engine and I can feel when its getting stale (motorbike)
 
donki said:
Blown engines but thats nitpicking.

An engine will run on 91, it will even run on diesel for a couple kilometres before conking out. Most cars that mandate 98+ fuel are able to detect if the octane is lower and either add more fuel and/or pull timing to adjust until the next tank.
I go through a tank of 98 every 4-5 days on a very high compression engine and I can feel when its getting stale (motorbike)
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OK. Enough said! Who is nitpicking? Consequential damage could be an issue
 
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peregrine said:
Thanks Spetz, all your point are spot on, I have had confirmation from two valid sources that my CJ MY15 Es has two maps. They say cleanliness only comes second to godliness? One big factor apparently worth doing is to decide 91, 95, 98 and stick to it chopping and changing wont only confuse you but could also confuse (oops wrong word) the ECU.
Click to expand...

There is one true way to find out, do a dyno test on standard fuel and go back once you have a full tank of 98 and do it again.

As I have said before, I am note sure how the low and high octane maps in a CJ work. (ie. does it always run on the high octane map and only switch down to the low octane map if it gets a dud load of fuel and detects knocking. Alternatively, does it after a fuel refill automatically go to its high octane map and then only revert to the low octane map after sensing knocking from a fuel with a lower octane than 98 having been put in)

Premium fuels though I believe have lower sulphur levels which is advantageous in some engines (probably not a worry to a 4B11/2) and depending on the servo may contain an additive package that has better detergents and/or friction modifiers.

Personally, when I had my CJ I always ran 98 "just cos". Did it do any benefit? Who knows... Being a bit older and more money conscious now, if I owned a CJ again I would probably just put E10 in it...
 
Ryan said:
There is one true way to find out, do a dyno test on standard fuel and go back once you have a full tank of 98 and do it again.

As I have said before, I am note sure how the low and high octane maps in a CJ work. (ie. does it always run on the high octane map and only switch down to the low octane map if it gets a dud load of fuel and detects knocking. Alternatively, does it after a fuel refill automatically go to its high octane map and then only revert to the low octane map after sensing knocking from a fuel with a lower octane than 98 having been put in)

Premium fuels though I believe have lower sulphur levels which is advantageous in some engines (probably not a worry to a 4B11/2) and depending on the servo may contain an additive package that has better detergents and/or friction modifiers.

Personally, when I had my CJ I always ran 98 "just cos". Did it do any benefit? Who knows... Being a bit older and more money conscious now, if I owned a CJ again I would probably just put E10 in it...
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Thanks Ryan. Dyno test is out not that concerned but will keep positive attitude towards 98, right or wrong and keep using 98.
Cost not concerned. Benefits? Hopeful.
 
The Checkout on ABC TV discussed fuel octane ratings. Their conclusion... 95 and 98 (for the majority of vehicle owners) are little more than marketing ploys. The octane difference does little-to-nothing for most vehicles, and certainly does not deserve its premium price.
 
bronzefox said:
The Checkout on ABC TV discussed fuel octane ratings. Their conclusion... 95 and 98 (for the majority of vehicle owners) are little more than marketing ploys. The octane difference does little-to-nothing for most vehicles, and certainly does not deserve its premium price.
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Most turbo engines and some performance engines have no option other than to use in most cases 98 octane petrol and would suffer if they didn't use it

So it certainly is more than a marketing ploy.
 
peregrine said:
Most turbo engines and some performance engines have no option other than to use in most cases 98 octane petrol and would suffer if they didn't use it

So it certainly is more than a marketing ploy.
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I think it's safe to say that The Checkout was talking about using higher RON 'premium' fuels in cars that do not need them. You've got to remember that the petrol companies market these fuels as being better for all cars and they would be mainly targeting the people that don't need the fuel (people that need it are most likely already buying it)...
 
The higher the compression ratio (absolute with turbo) , the higher the required octane needed.


I don't need to but use 98 octane for the benefits I gain and which others in these and other forums appear to have benefited from.

Perhaps not cost effective. BUT!!!!
 
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Interesting! In last Nov: Wheels mag: Road test (certainly not comprehensive) on a Peugeot 308 1.2 ltr: turbo, showed improvement
in cost using 98 octane as against 95 octane fuel.

For every 500km, A saving of $3.25 using the 98 octane which is about $130 for 20000km plus whatever other benefits the higher octane fuel offered.

Not Bad!!

Also the comment, that the reason for so many manufactures moving to smaller turbo engines is economic not economy
as lower emissions rating means higher sales, in many countries due to tax breaks.

So we have to suffer the consequences Down Under. Thanks Mitsubishi for sticking to the NA 2.0 ltr: and 2.4 ltr: instead of a smaller turbo
that will wear out so much faster and cost so much more to maintain over time. Not just the turbo But also the smaller motor adding to the problem.

Direct injection would be nice.
 
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