I've done a test with all the cars i have owned, and they all increased in economy by 5 - 10 MPG.
Im doing a complete engine service on my 1995 1.6 single point injection VW polo over the weekend....
Once I am done, is it worth switching to premium octane fuel?....I do like to give the engine a good spanking so would this fuel help preserve the
engine and give any more beans?
Im only going to be keeping the car unitl I can find a suitable replacment with a lot more power in it....
Any thoughts appreciated.
Dunc
Higher octane fuel allows you to run higher compression or more advanced spark timing withought causeing engine knock. If your engine will run at
full performance on 95 then there is no point in buying 97 RON.
Better quality fuels often have more detergents and other additives that will keep your engine nice and clean.
Well it's certainly different. I once filled my buggy up with special shell stuff and ended up have to drain the tank as the engine could barely
maintain an idle.
I have tried another one in a bluebird, can’t remember which garage and the idle speed this actually increased and the car did have a little more
power but not much so now I just use the cheap stuff.
only really worth it if the car is spec'd for higher than 95ron or engine is mapped to suit.
Didnt a car magazine run a test on all the premium fuels. Im not sure on the details of the test, but Im sure they were running cars back to back on
dynos with different fuel.
Apparently Tescos 99ron came out top.
Can newer car ecus detect higher octane rating in fuel? Just wondered if they could then I would imagine the power increase would come from an advance
in ignition timing.
[Edited on 22/3/2007 by greggors84]
Definately worth it whatever car you use. the price difference is pretty much matched by highter MPG and the inlet valves will have a reduction in
deposits from the fuel and therefor increasing the life of the engine.
I've done a test with all the cars i have owned, and they all increased in economy by 5 - 10 MPG.
quote:
Originally posted by greggors84
Didnt a car magazine run a test on all the premium fuels.
Apparently Tescos 99ron came out top.
quote:
Originally posted by 02GF74
quote:
Originally posted by greggors84
Can newer car ecus detect higher octane rating in fuel? Just wondered if they could then I would imagine the power increase would come from an advance in ignition timing.
quote:
Originally posted by mcerd1
Yes - some very new ones (last few years only) but even then you won't see much power gain unless it can increase the CR or boost
so turbo cars with modern ecu's it can make a big difference to power
My daughter's Golf GTi Turbo will adjust its timing according to the grade of fuel (presumably knock sensing), and if you want the full rated
power you must use super unleaded. It gets standard unleaded when I fill it up!
However my locost MUST use it - it's an unleaded conversion and I've kept to the leaded ignition settings. It does NOT like the regular
unleaded! 
quote:
Originally posted by speedyxjs
Definately worth it whatever car you use. the price difference is pretty much matched by highter MPG and the inlet valves will have a reduction in deposits from the fuel and therefor increasing the life of the engine.
I've done a test with all the cars i have owned, and they all increased in economy by 5 - 10 MPG.
Makes a lot of difference on older engines, and then it depends how they are tuned up. As others have said knock resistance goes up with the octane rating. I set my engine up on Shell V Power, 101 octane (basically the equivalent of old 5 star) and the pinto loves it.
My V6 was mapped on high octane Shell Vpower to get a few more horses. If I fill up with standard unleaded it tends to pink under load when hot so I
will only use it when I can't find the high octane.
If your engine is in standard tune then the high octane stuff is just a waste of money imo, and you only need to use it if you are running high
compression or excessive advanced ignition.
I work at an engine management tuner, as I understand it on most engines there is little point running high octane fuel, the only benefit you might
get on your first tank of optimax is that the detergents would give it a clean-out. But then you could happily go back to the cheap stuff.
In theory a modern ecu with knock control could learn to your fuel and advance the ignition so you got more power. I have seen some ECUs with those
facilities but only used to reduce power in case of crappy fuel, they would not actively take advantage of higher than 95 octane (fiesta ST150).
I have yet to actually work on a car that does learn up to higher octane fuel so I couldn't say which models will.
Surely any car with a knock sencor will benefit from Higher octane fuel...
Aren't their ECU commands that when all the temperature restraints etc are met is to advance until it pinks and then retard back a few degrees...
wait and then try again.
My XE engine likes a drop of the good stuff and I'd say I got a further 50 miles out of a tank full in very hot conditions and it idled better
and didn't need to be caught by the anti-stall when backing of the throttle quickly.
But as for an older car thats timing if fixed.. other than for its cleaning properties it would be a waste to run it full time
flak monkey where do you get all the wonderful pictures for your avatar? I think we all want to know.
ERM!!! Did everyone else miss it????
Flaks new Avatar is like sex on a stick!! Very nice!!
Some come from my missus, the current one is from:
http://www.scar13.com/
Which is most definately NWS! 
quote:
Originally posted by MkIndy7
Surely any car with a knock sencor will benefit from Higher octane fuel...
Aren't their ECU commands that when all the temperature restraints etc are met is to advance until it pinks and then retard back a few degrees... wait and then try again.
If anybodys still reading this topic....
Could Running the Higher Octane fuel cause the car to run hotter?
Or the Idle to be worse if the car does/doesn't take adavantage of the Octane.
I ran My XE engined car on Tesco 99 octane over the weekend on a trip to Wales and it sempt to be running warm and wouldn't idle properly (It
hasn't got a Lambda so can't be the dreaded silicone fuel!)
Nope, it shouldn't make any difference whatsoever - it just a waste of money unless you have retuned to take advantage of the higher octane.
If your car is mapped for 99 octane, you can run on the cheaper stuff in an emergency but I wouldn't do any drag strip runs
The XE engine has a Knock sencor on so i'm presuming it can adjust its timing accordingly.
Doesn't advanced timing cause higher engine temperatures?... and a poor idle if too far advanced?
AFAIK the knock sensor will only retard the ignition back from the initial map setting so if it was mapped to run on 97 octane you might get away with 91 octane but it might revert to 'limp' mode.
I once filled up an old Golf Driver of mine on Super and it ran like a bag of pooh, I have to admit that I did it by mistake though, so wasn't
too bothered - I just wish that I hadn't put in an ABSOLUTELY FULL tank!
I did run my last RACE/TRACK Bike on it and then I incurred some stuttering whilst driving out of corners, I don't know if this was 100% to do
with the change in the fuel or a problem with the bike in general! I was getting 2.00 min laps of Oulton on a pile of crap Yamaha Thundercat!!!
Steve.
Hmm, being a Astra GTE engine and no Cat It might well have been Tuned for 4 star as its maximum octane... if it does only retard from its maximum set
rating.
It definately wasn't running in limp home mode cos as WorX said it Went lke sh*te off a shovel it just wouldn't idle.. bit like a race car.
Although it is the first of the hot weather we've had for a while and it is running without the Oil cooler it appears to so desperately need!,
the oil thinned out drastically when stuck in traffic, never seen the pressure go so low.
quote:
I ran My XE engined car on Tesco 99 octane over the weekend on a trip to Wales and it sempt to be running warm and wouldn't idle properly (It hasn't got a Lambda so can't be the dreaded silicone fuel!)
My pinto was designed to run with 4 star and 12°BTDC timing, but 8°BTDC if running unleaded.
If I use 99 octane, can I revert back to 12° and reap the performance benefit?
I think I probably can!
quote:
Originally posted by Mark Allanson
My pinto was designed to run with 4 star and 12°BTDC timing, but 8°BTDC if running unleaded.
If I use 99 octane, can I revert back to 12° and reap the performance benefit?
I think I probably can!
quote:
Originally posted by David Jenkins
My Megajolt can now run with 2 maps switchable on the go - I'm going to use the 2nd one for times when I can only get regular.
) and a balls out map with loads of boost for
track days.