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95 Octane fuel?

Discussion in 'Performance' started by LonePiper, Mar 21, 2014.

  1. LonePiper

    LonePiper Member

    Messages:
    24
    Location:
    Geelong
    I've recently been recommended to switch from regular 91 unleaded to 95, which I have done (hurting a bit on the price rise)
    I worked out just before the switch I was getting a bit under 15 litres per 100kms, highway driving which I think isn't too bad.
    I haven't done a comparative amount of highway driving since then to compare the consumption.
    However, it might just be my imagination or the increasing cold weather, but I get the feeling since I started using the higher octane fuel, my engine has been popping and spluttering and farting a bit more often. It doesn't do it much, but it's often enough to take notice of, and while it has always done it, I get the feeling it's slightly more often than usual. It tends to happen at the usual times - going up hills or on cold mornings etc.
    I know my engine isn't tuned to perfection at the moment and needs some degree of attention, for the record.
    Is this natural and just a result of needing to run on the new fuel for a bit to "flush the engine" through so to speak? Or could something else be going on?
     
  2. syncro

    syncro Well-Known Member

    Messages:
    10,243
    Location:
    Southern Highlands
    You are unlikely to get much of a performance or economy increase with higher octane fuel but you will not cause damage or excessive wear to your engine as you would with 91. Cheaper long term.
     
  3. Syncro27

    Syncro27 Well-Known Member

    Messages:
    6,602
    Location:
    Terrigal, NSW Central Coast
    I run 95 in my 1641 lowie and get around 11L per 100kms. With the old engine I used the 91 (before the 10% crap was added) and it pinged, had a rough idle and got terrible economy.

    I would say the new donk fixed most of the problems but the power and economy is great on 95 - for me anyway.

    I wouldnt touch 91 anymore as its near impossible to get without ethanol, you get no power out of it and it slowly clogs up and destroys you engine.

    As Phil says - it will be cheaper to use in the long run.
     
  4. cbus

    cbus Well-Known Member

    Messages:
    13,474
    Location:
    sunshine coast
    I have found 91 [without the alc] to perform poorly on engines designed for it . [non vw][pinging] this was a common issue upon introduction of the unleaded 91.
    Also my air cooled EFI motor nearly stops on it and is fine as soon as 95 used. [repeated a few times under controlled conditions to check][poor ignition of fuel. but same electrical ignites LPG no problem and it can be hard to ignite at lower ratios and engine speeds],
    I believe the solvents used to formulate 91 to be inferior to 95 or 98. so the issues are not just related to octane rating.

    the higher 'euro'standards engines had to have the newer fuels [95 /98 ] to achieve emissions standards.

    some peoples engines run fine on it . possibly due to a lower compression or general timing/condition in the engine. long term issues unknown.

    I cant explain why you are getting potentialy problems with the 95 but would suggest any similar issues may indicate plugs/leads/cap may needing replacing along with a general tune up to check electrical and fuel delivery mix. A can of complete fuel system cleaner may be helpful but the new fuel is often used to perform that function in the past. Can only assume it helped ?

    The 95 will certainly do no harm and may give better economy due to better running in most cases but no gain from octane change unless the engine can take advantage of it via additional advance or compression increase.

    I would be looking at ensuring fuel system is clean and mistures correct, no breakdown in electrical system under load[observe at night for stray sparking on HT wires] , vacuum leaks [hoses and manifild/carb gaskets, worn throttle shafts], valves set correctly , clean oil ,as possible issues relating to the popping


    But with your history of vw Im probably waffling to the converted :lol:

    cheers
    col
     
  5. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    7,016
    Location:
    Gosford
    In the manufacturers instructions that have come with all my past T3 Caravelle's 1989.1990 & 1991 specified 91 Octane and I ran my first 2 Caravelle's on 91 clocking up 150k klms without a twitch. HOWEVER that was back then and as they say oils aint oils. Production of fuel has probably changed since then. I can still easily get 91 octane unleaded with no Ethanol. I have noticed over the last few years that my T3 would run a little underpowered :) on 91 but no pinging or other audible effects. Solely on the advice of the general T3 population I come in contact with I have for the last 3 years been only useing 98 octane or if unavailable 95. Do notice 30 or 40 more k's travelled per tank on the 98 and seems to run nicely. Have yet to meet a single person who has said 91 ruined my motor but hey I dont want to take any chances :)
     
  6. slobus

    slobus Member

    Messages:
    191
    Location:
    NW Tassie
    Similar story to Luckyphil, although was reading recently that despite the slightly higher cost per fill, you actually get more km's per year....so from memory over a year you're less than $5 out of pocket moving up to 95-98 (don't quote me but it wasn't much!). I run my daily drive 1600 single port beetle on 95/98 with no issues, 91 and it seems to run a bit rough and down on power...only marginal (it's no pocket rocket!!).
     
  7. andrewjdriscoll

    andrewjdriscoll Active Member

    Messages:
    279
    Location:
    nelson bay, nsw
    Hello all,

    I drive a '72 Microbus which I purchased from a very fastidious one-owner in 2012. It still has the original decal on the inside of the petrol flap that specifies a minimum octane rating of 92. Have always used 95 or 98. Have driven 1200kms over the last week and a half averaging 10.5 litres per 100kms. This has improved from about 14 litres since a new brake booster was installed and a subsequent tune was done about a month ago.

    AJD
     
  8. andrewjdriscoll

    andrewjdriscoll Active Member

    Messages:
    279
    Location:
    nelson bay, nsw
    Sorry I have to correct myself. That should read minimum octane rating of 91 Ron. Never used it 'though.

    AJD
     
  9. syncro

    syncro Well-Known Member

    Messages:
    10,243
    Location:
    Southern Highlands
    The problem is that 91 is usually less than 91. VW say minimum 91.
     
  10. Alpal

    Alpal Moderator Staff Member

    Messages:
    8,987
    Location:
    Melbourne Bend of Islands
    Run our 79 on 91 and its tickety boo. Others insist higher octane makes a difference. Buy and try!
    Only limitation is that ethanol fuel is not advised. May rust metal tank?
     
  11. LonePiper

    LonePiper Member

    Messages:
    24
    Location:
    Geelong
    Thanks for the feedback guys :)
    It seems, as I expected, that after running it through for a week the performance issues have resolved themselves, and even seem better than before; it's not running on or pinging nearly as badly as before.
    I'll have to do long highway trip in the near future to see how it's affected my economy, but my feeling is that is better as well.
     
  12. da split

    da split New Member

    Messages:
    23
    Location:
    newcastle nsw
    G'day mate. Thought I'd pipe in on the conversation, I work for a large fuel manufacturing company and deliver all the fuels your talking about.
    Ethanol blended fuel is actually 89 and then the octane rating is boosted to 91 to meet the aus standard.
    Ulp is your standard petrol and is fine to run on almost all engines except for high performance motors.
    95 octane fuel is by far the most popular choice by motorists as it gives better fuel economy than 91 as well as it generally cleans carbon deposits ect from fuel lines tanks ect to keep everything clean.
    98 octane fuel is again for higher performance vehicles as the octane in this type of fuel burns hotter, in my opinion a kombi motor doesn't need this high I a grade fuel and I think you would be wasting your money.
    Ethanol fuel or e10 as you would know will deteriorate the inside of your fuel tank and perish your fuel lines ect with time, we have had to replace so many storage tanks because of this corrosion effect.

    To get the best fuel economy and keep your engine happy I would use 95 octane from either shell or Caltex not bp as all there fuels have ethenol in it to some degree.
    Have your engine tuned to this higher grade fuel and replace your fuel filter after you have ran a few tanks through it so you can start with a clean one hope this helped you out cheers

    Regards da split
     
  13. 1500king

    1500king Well-Known Member

    Messages:
    1,617
    Location:
    Adelaide, SA
    15L/100 is a bit rich...

    Sounds like it is running richer with the 95, pushing the motor into rich misfires. You have a carburettor problem(s).

    I have no dramas with 95...but for my daily drive Micro, on warms days I find 95 is not enough , so I jump to 98...but it is not quite standard either.

    With a correct working distributor and carburettors, standard motor, you should have absolutely no problem with 95 and in most cases, no problem with 91(unless it has ethanol in it which most do).
     
  14. 1500king

    1500king Well-Known Member

    Messages:
    1,617
    Location:
    Adelaide, SA

    Some misinformation above IMO... Correct in that fuel economy should be better with 95RON but is any of the fuels have ethanol in them and is doesn't matter which RON, then it will have a lower air/fuel ratio. Therefore, with the fixed jets in your carbureted motor, it will run LEAN and produce a hotter burn(like blow torching) on all grades of fuel.

    The RON(research octane number) was just created by the SAE(society of Automotive engineers) as a measure of a fuels resistance to detonate in the chamber (or knocking/ pinging as it is sometimes called).

    98 is perfectly fine for your motor, it does not burn hotter but longer. If you need the detonation resistance on your motor, even when the AFR's are correct(under power 12.5-13.0:1), then just use it(high load, higher compression engine which has a susceptibility to detonation due to more localised hot spots, faster burn rate from the more dense mixture, therefore less time to the max thrust on the piston).

    If you have 98 that has ethanol in it, you may find that your motor will still detonate as the Stoiciometric AFR of say E10 is 14.1:1. Therefore while your motor is loading itself up going up a hill, the E10 will be squeezing itself at the same volume through the main jets as you would with 14.7:1 petrol. Your loaded AFR is then all of a sudden outside of the safe region of richness under power for any aircooled(standard and modified) where it becomes much like pointing an oxy torch at your cylinder heads as heat spirals out of control. This is where head failures, piston melt downs, etc, come in.

    E10 isn't too bad on your fuel system...The problem is that so many people are running around with unserviceable and aged fuel systems with old rubber technology. I still don't go near it though(you can smell it at the servo). The modern carb kits use NBR(Nitrile Butadene Rubber) diaphragms, nitrile/viton o-rings and as long as you use the same (Eg, ContiTech NBR braided hose or an equivalent EFI hose ), then you will be fine. What is unacceptable is when you let the car sit and let the fuel absorb water..... then you start to get corrosion issues with the addition of a much more active electrolyte. Alcohol is not far off the conductivity of petrol...it is the water that is the killer. Much like Servo's with leaky bulk tanks.

    If you are scared of running lean due to not being able tell what fuel is going into your tank, then go up a main jet size in the carburettor.
     
  15. LonePiper

    LonePiper Member

    Messages:
    24
    Location:
    Geelong
    Yeah, I figured my engine/carbies are not perfectly tuned. I'll have to look into it in the very near future. Cheers!
     
  16. da split

    da split New Member

    Messages:
    23
    Location:
    newcastle nsw
    I'm going to have to disagree with some of the above comments
     
  17. Syncro27

    Syncro27 Well-Known Member

    Messages:
    6,602
    Location:
    Terrigal, NSW Central Coast
    My 4 stroke lawnmower is a good indicator of this and while it is just a mower it has a very similar carby fed 4 stroke engine to an aircooled VW but with 1 cylinder.

    I have only a 5L spare fuel tank that I top up my mower & 2 stroke whipper snipper with (then add oil to the 2 stroke motor whipper snipper as required) which takes ages to use as the mowers only have a small yard to deal with with slow growing buffalo grass. However, I always noticed my mower ran slow and back fired and struggled with long grass as I was using 91 fuel in it. Since the spare tank ran out I filled it with 95 unleaded and what an instant change for the better. It runs much faster, copes easily with long grass now and doesnt backfire and starts easier when run on 95.

    The whipper snipper was the same story.

    It was a truly amazing difference.

    I wont be going back to use 91 ever again E10 or not.
     
  18. 1500king

    1500king Well-Known Member

    Messages:
    1,617
    Location:
    Adelaide, SA
    Try it on the Dyno. ;)

    You have every right to disagree! It's your engine! :p
     
    Last edited: Mar 27, 2014
  19. 1500king

    1500king Well-Known Member

    Messages:
    1,617
    Location:
    Adelaide, SA
    Yep, lean misfires.. then backfires as they ignite in the hot exhaust..Putting the engines under more load makes the problem monumentally worse.
     
  20. KahunaKombi

    KahunaKombi Super Moderator Staff Member

    Messages:
    22,220
    Location:
    Bracken Ridge, Qld
    I had probs with starting the Rover 4 stroke mower, Shindaiwa 22T whipper snipper and Stihl blower so all name brands and none cheap but I changed spark plugs to NGK from Champion and what a difference that made and now only use NGK in these and also the Pole Chain Saw (BBT - it's a great toy) and the Ross chainsaw (cheap and nasty but does it's job).

    Do not think in Qld we have E10 91 RON anymore but they may be just hiding the fact of E10. Might give the 95 a go next time I need to get fuel for the gardening tools :cool:
     
    Last edited: Mar 28, 2014

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