Fuel Again
Submitted: Monday, May 15, 2006 at 18:19
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If we forget about cost and perfromance is there any engine or other component benefit from running 98 RON when the vehicle will run on 91 RON?
Reply By: Member - Oldplodder (QLD) - Monday, May 15, 2006 at 19:10
Monday, May 15, 2006 at 19:10
If it runs a carby, or possibly early fuel injection, and has a compression ration less than 9:1, possibly not, unless you are willing to specifically tune the engine to suit.
If it is reasonablt new and is able to sense oxygen in the exhaust, or better still a knock sensor, it may benifit from PULP, since the engine management system could advance the timing to take advantage of it.
Bit of suck it and see. There is not a general rule.
AnswerID:
172823
Follow Up By: GaryInOz (Vic) - Tuesday, May 16, 2006 at 13:31
Tuesday, May 16, 2006 at 13:31
"...it may benifit from PULP, since the engine management system could advance the timing to take advantage of it...."
You mean "...IF the engine management system could advance...".
EFI systems work to a "map" stored in their memory. Most systems have a preset "maximum" advance for the ignition, at a given load/throttle position/RPM usually calibrated for standard 91 RON fuel. Even when fed the 95/98 RON fuel, unless the ECU has been altered in some way, the maximum timing advance point will still be the same (as per the map). The timing will be retarded (taking inputs from the knock sensor) if the fuel is not even up to the 91 RON standard to prevent pinging (minus one or two RON points).
Having said all that it is possible for a vehicle to have an ECU set up for PULP 95-98 RON but with a wide enough internal "map" to be able to handle 91 RON based on inputs from the knock sensor. The ECU has to take some time learning the fuel characteristics, but they usually try to keep the ignition timing at the peak of what the fuel (or blend) can do, so if you fill up with PULP it will "come to life" again after running on ULP.
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Reply By: Scubaroo - Monday, May 15, 2006 at 23:19
Monday, May 15, 2006 at 23:19
Best thing to do is do 3-4 tankfulls of ULP, and then similar distances on 95 and 98. I use Shell Optimax on my 3.5L Pajero - get better economy around town, and far better economy on the highway, and there's noticeably more power. Both around town and on the highway, the cost per km works out cheaper to run PULP. So I run it all the time. Never got around to trying 95.
It seems that it's particular to each make and model - there's no clearcut yes/no answer in general.
Wish I'd known about WRXs running fine on ULP - I get the same economy out my Pajero as I did that thing when I had it.
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172876
Reply By: Member - Heidi L (NSW) - Friday, May 26, 2006 at 15:36
Friday, May 26, 2006 at 15:36
I found the Kluger ran better on the 98. There was a while you couldn't get PULP in
Sydney for a few weeks and it was definetly noticable in performance.
I also found the Check Engine light came on if I filled up at a smaller petrol station like on
Fraser Island, or country towns if it did not like the quality of the fuel.
AnswerID:
174931
Reply By: Alloy c/t - Friday, May 26, 2006 at 16:25
Friday, May 26, 2006 at 16:25
Next door neighbour is a mechanic [or should I say technician] whose private vehicle is a 98 pajero 3.5v6 ,he would only ever use the premium priced 98 ron as he claims is better for his motor and gets better fuel economy than using "standard' 91 ron ulp,, on a recent trip when time to refuel no 98 was available so in went the standard 91 ron ,, he is now saving the odd $ and getting an extra 50/60 klm for the same amount of litres/ tank ,,,would seem that the best fuel rating to use is the one that the vehicle maker recomends ,in this instance the handbook states 91 ron as the minimum.
AnswerID:
174933