BHORT

Barry K,

Do you know your actual mpg value using super unleaded, it is hard to judge from the amount of miles per tank full as it depends how low you go prior to filling up.

Otis

Thinking of giving super unleaded a go. Is it as simple as pulling up at the pump? I seem to remember previous threads on performance problems especially when changing back to normal unleaded and tips of disconnecting the battery to reset....etc.

Any experiences/comments?

Ta,

Otis.

BarryK

Apart from the cup full in it when I picked it up from Robinson's Rochdale, I have always put SUL in it. I know blah blah runs on 95 RON ECU mapped etc etc, but I understand the ECU adjsuts to what is going on around it (similar to what Hyundai are now advertising as "a self tuning engine").

Whatever, I get 300 miles per tank no problem, even if I go "native" a bit. How does that compare to your MPG? The car accelerates very smoothly, I have never felt the "hunting" problem like you described a way back.

Switching from 95 RON to 97 RON, from a sampling point of view for the computer, will take it absolutely yonks to appreciate that the fuel has permanently "improved". That's why the holy grail of resetting is recommended so the measurements start from scratch, appreciating and reacting to better samples sooner.
Without knowing the full ins and outs of Subaru's ECU programming, I would assume there is a limit to which this effect can be increased in a standard UK set up car, probably with a hefty wedge of tolerance in favour of the mechanical components, hence they rarely break.

From what I've read the higher RON makes the fuel less likely to detonate in the cylinders of it's own accord, (which I think is what is called knocking by car mechanics and the like), which makes the timing of the combustion process more controllable so the engine system can deliver better power without destroying itself. If knock is detected the ECU will dynamically retard the ignition timing to avoid personal destruction, the reverse process however is not so dynamic.

Well whatever the low level inaccuracies, I'm convinced, and my tail pipes are always full of soot!

Anyhow, despite all of the above, as you are well aware, I have photographic evidence thatyour car is faster than mine.

boomer

Heck, 300 miles a tankful would keep me happy!!!

Maybe i should give SUL a try - i lose money on the company mileage rate anyway, so what's a few pence more? Do you (as Otis asked) really have to reset the ECU to get the best gain?

mb

DocJock

Boomer,

If you want to try an ECU reset check out the FAQ on the SIDC site. It apparently can be done by disconnecting the battery for about 20mins if I remember correctly. Haven't had cause to try it myself.

BarryK , most people responding to previous posts on mpg seemed to get not far either side of 200 miles/tankful.

Personally have only ever run SUL but adding Millers CVL (+2.5 octane points) for track use gives obvious improvement in smoothness and pickup, wouldn't know about mpg though.

Regards, John

BarryK

OK I got 310 miles from full to cacking myself with the light on last December. (It filled up with over 56 litres) I now judge the miles, trying not to run it way down. At 275 to 280 now I go fill up again, but I work with that 20 mile reserve. I don't clog it too much and change gear regulalrly. Most of the time that is. I drive over uncluttered A and B roads around half my journey to work, 30/40 urban bits, (at 07:30 ish) and come home on the M62. I do very little urban crawl type driving, generally none at all. I have noticed that driving short distances considerably knocks mpg.

My round trip journey to work is 70 miles and I know I can do four days without visiting Mr Shell.

boomer

I don't mind giving the ECU reset a try, but if SUL isn't always available, then i don't want to compromise settings by flipping between normal and super.

Does SUL give a benefit on it's first use, or does it require "breaking in"? Can i mix std and SUL between fillups without causing harm (but still getting a benefit)?

mb

James Neill

iTrader: (1)

I posted a similar message and got a reply directing me here

BarryK

Boomer, no, as I understand it, once you put 95 RON in and the ECU detects the "inferior" fuel (ie knock) it retards everything and will take an infinity of sampling to get its nerve back!

Iain P

Anybody know where the connectors are for a 99MY?

Cheers