Performance Cars - Can You Tell The Difference between 95 and 98 Fuel?

Wampus on 26/07/2018 - 10:07

Hi all

I was talking to a friend who drives a nice Focus RS, and we were discussing the cost of fuel. I respect his opinion as he's quite knowledgeable, and he was saying he usually just puts 95 in his car instead of 98, because he can't tell the difference, and that only highly tuned vehicles can really make the most of 98.

However, I'm sure my car has more power when I put decent 98 fuel in, instead of the usual 7-11 95. I drive a Subaru Levorg with a few tweaks. Am I imagining it? I'm not, am I? Right? I'm right, aren't I?

Automotive Car Fuel

Comments

  • dcep on 26/07/2018 - 10:09
    +9

    depends on your car ecu able to adjust timing by itself or not.

  • [Deactivated] on 26/07/2018 - 10:14
    +1

    My car tells me "low octane" if I use anything other than 98. Even some 98 flashes (typically caltex).

    If the car goes into low octane mode, it's fairly obvious. Not as bad as limp mode, but no joy to drive.

    Ps. I'm surprised there are still focus RS without a blown up head gasket. Glad it is not your car. It's a lemon by design.

    • dcep on 26/07/2018 - 10:19

      what car do you drive ?

      • [Deactivated] on 26/07/2018 - 11:28
        +6

        The one with the octane sensor is a LP570 with a custom tune for 98. Default is 100+ which meant every servo outside the racetrack threw the error.

        I don't drive that anymore though. I've gone road legal track car :) much more fun (cause I don't care what happens to it).

        • jobski on 26/07/2018 - 11:32
          +6

          A true ozbargainer would custom tune it to 91 or convert it to gas.

        • [Deactivated] on 26/07/2018 - 11:34

          @jobski:
          Nah. I'm a tightarse. I got the dealer to source and front the custom tune because Aussie servos don't have 100+ by default.

          Bargain!

        • vinni9284 on 26/07/2018 - 13:41

          Have you considered a twin turbo kit like you see in OS/Youtube clips?
          They get ridiculous power when you chuck those in. Even without it they have crazy power.
          Cheers

        • [Deactivated] on 26/07/2018 - 15:30

          @vinni9284:
          I usually have my car "detuned" (still stage 2/3 but conservative). Not a fan of overboosting and turbo lag.

          I have driven a ridiculously overboosted mk6 R (APR turbo kit with the lot). Nearly shat myself out of a corner.

        • vinni9284 on 26/07/2018 - 19:32

          @tshow:

          overboosted mk6 R

          Wow .. nice.

          I'd still rather the LP570 with TT :P …. wearing a neck brace!

          Wooooow

          I am not sure if I can place the link here however there is a White 2K HP lambo convertible that passes top ended bikes flying on the freeway stand-still on You Tube .. even the bike rider shakes his head in disbelief!

          Cheers

        • vinni9284 on 26/07/2018 - 19:32

          Dupe - Removed

        • braskic on 27/07/2018 - 08:10
          +3

          Have you considered a unit sticker on your back windscreen and a Chevy badge? Extra power and change from a fifty.

          Cheers

        • [Deactivated] on 27/07/2018 - 08:49

          @braskic:
          I've always debadged my car where possible. Too bad the make badge cannot be removed without it looking like a stolen car.

          So yeah. I'll pass on adding badges but I'll take your word re extra power. :)

        • boostpak on 28/07/2018 - 08:31

          @jobski: lame af

  • Pootie Tang on 26/07/2018 - 10:15
    +7

    Short answer, "yes" with an "if"; long answer, "no," with a "but"

    • mingofmongo on 27/07/2018 - 08:26
      +1

      thankyou Reverend Lovejoy

  • plmko on 26/07/2018 - 10:16
    +5

    Your friend drives a Focus RS……and is concerned with the cost of fuel, he can't be serious right?

    • Wampus on 26/07/2018 - 10:23
      +1

      The cost of fuel in general, compared to a few years ago

  • dresh on 26/07/2018 - 10:17

    I didn't believe it either at first, but now I only use 98. I haven't noticed anything different in fuel consumption but the acceleration is much smoother

    • Wampus on 26/07/2018 - 10:24

      I get more power lower down on 98, I'm sure of it.. and yeah, smoother. What do you drive?

      • dresh on 26/07/2018 - 10:50
        +1

        Clio RS, so it's tuned to run minimum 95 already

  • pegaxs on 26/07/2018 - 10:24
    +20

    Another thread where the bogans in their 285,000km BA Falcon shitboxes will swear black and blue that they get more horsepower from 98…

    Higher octane fuel does not have more bang in it, it just resists pre-ignition (pinging/knocking) under higher compression. 91 and 98 has the same energy density per litre/kg as each other.

    The difference comes from the engine being able to make use of the ability of the fuel to resist pre-ignition. If your car is tuned to run on 91, there is absolutely no benefits to wasting your money on buying 98. It does not have "moar powa!!!"

    On the flip side, if your car is designed and/or tuned to run on 98, do not run it on 91. It will possibly cause engine damage and will run like shit. Not because the fuel is low in energy density, but because the ECU will have to adjust the timing so much that it will limit power to stop the engine pinging and minimizing damage over performance…

    • Wampus on 26/07/2018 - 10:33

      I agree with you re the 91 - my ex put 91 in the Levorg once and it pinged like a bastard.

      Do you have an opinion of cars like mine which are tuned for high octane fuel, for a difference between 95 and 98?

      • pegaxs on 26/07/2018 - 11:18
        +2

        If it's tuned for 95, run either. If it's tuned for 98, run it on 98 and nothing less. If you have a "few tweaks", then sure, 98 can't hurt.

        You will not get more power from your 95 by running 98, all it will do is cost you more money for no gain.

        But if your brain tells you that your butt Dyno notices something and you're happy burning the extra coin on fuel you don't really need, then have at it. There is no problem burning higher octane fuel in any car, other than the economy of doing it.

        • Hirolol on 28/07/2018 - 10:30

          Hi
          You seem to know your shit so can I ask an unrelated question about fuel?

          I have seen bp claim that their premium fuel can somehow “clean” an engine after x amount of litres used. Do you know how legit this is?

        • pegaxs on 28/07/2018 - 11:26
          +2

          @Hirolol:

          You seem to know your shit

          Cheers… But some bogan morons on here would beg to differ. :D (I have been in the automotive industry for a long time…)

          As for how "legit" the whole "cleaning" claim is, to me, it sounds like marketing bullshit. Here is why I think this…

          Fuel is a solvent. So, by its own nature, it is a cleaner. So, you pour solvent in your tank and it goes down the line. Through a filter and off to the injectors. Where is this "gunk" coming from? Unless there is water/dirt/crap in your fuel and that crap is allowed to sit for a long time in your fuel lines, there is no "gunk" build up… Fuel by its own nature already does a great job of cleaning as it gets pumped through your car… Regular servicing and changing the fuel filter on regular intgervals would do a better job than some miracle, bullshit snake oil that BP is trying to convince you to buy…

          As for cleaning out your engine itself, this is even more bullshit. The fuel only ever enters the combustion chamber. While a small portion of it may not get burnt, 99% of it does. What little that is left over that is unburnt, 99% of what is left gets pushed out the exhaust port. So, the 1% of the 1% that doesn’t get burnt or pushed out the exhaust, may find its way past the rings and into your engine. There, it will mix with the oil and start to break down the oil (this is part of the reason you need regular oil changes.) What it does NOT do, is get into any other part of the engine and clean it. Cleaning the inside of the engine is the job of the oil.

          BUT! And here in lays the crux of the issue. Yes, there are bad quality fuels, and these bad quality fuels can burn like crap and leave carbon deposits behind on your piston crowns and valve seats. This is not a good thing. The thing is, most fuels in Australia already contain additives to minimise this carbon build up around your combustion components. The best thing to do is fill up at a reputable fuel supplier. Go to a place that you know sells "clean" fuel, with as little water, dirt and garbage in it as possible.

          So, as for BP fuels claim that their fuel cleans your engine over 2 tanks, this is nothing but absolute, pure A grade marketing BULLSHIT to get you to buy their very, very expensive 98RON fuel. Their other fuels still have the detergent additive in it, and as we have seen, good servicing, regular filter changes and using a reputable fuel supplier are more important than paying a 20c/l+ premium for their marketing bullshit…

          If you don’t want to read all this, you can listen to everyone’s favourite vitriolic divider of opinions, John Cadogan… BP's BS: Advertising Fail

        • Hirolol on 28/07/2018 - 15:11
          +2

          @pegaxs:

          If you don’t want to read all this

          I read it all.
          As I was the one that asked the question, if you have gone to the effort to type out a detailed response like that then you deserve to know at least one person has read it.

          Thanks! Everything you said makes total sense.
          I had the suspicion that it was total bs.

        • pegaxs on 28/07/2018 - 17:34

          @Hirolol:

          All good. Thanks for reading. :)

        • JIMB0 on 29/07/2018 - 08:45

          @pegaxs: A bottle of injector cleaner added to U91 does a better job of cleaning than U98 on its own.

        • pegaxs on 29/07/2018 - 09:57

          @JIMB0:

          Yep, I totally agree, Jimbo. It’s anywhere from $7 to $25 a bottle though. But considering it doesn’t need to go in every fill up, at the price difference in 98 to other fuels, it would only take 1 or 2 tanks to be well back in front on cost savings…

        • Hirolol on 31/07/2018 - 06:39

          @pegaxs:
          Will the e10 ethanol fuel do damage to a car?
          Could probably add this cleaner in to mitigate it?

        • pegaxs on 31/07/2018 - 10:44

          @Hirolol:

          E10 fuel will only damage cars that are not designed to have it in there. Most newer cars are ok with E10. You can usually Google your car and find out if it will run on E10.

          Anyone that tells you that E10 is a dirty fuel, is mildly retarded. All I usually hear when uneducated morons talk about E10 that they obviously just regurgitate bullshit they heard from another moron is a lot if autistic screaming…

        • Euphemistic on 31/07/2018 - 18:57

          @pegaxs: and my understanding is that the ethanol would be an extra cleaner if anything.

        • pegaxs on 31/07/2018 - 20:54

          @Euphemistic:

          Exactly. Ethanol is known by another name that people aren’t so scared of called… “methylated spirits”. And it is a great cleaner…

        • Hirolol on 01/08/2018 - 07:40

          @pegaxs:
          Looks like my car can take it.
          Thanks again!!

    • zeomega on 27/07/2018 - 23:24

      Major brands also throw in some additional detergents in their chemistry for 98. Much of a muchness tho.

    • [Deactivated] on 21/08/2018 - 10:25

      Thank you for the authoritative and helpful comment.

      Are you able to help advise… with a Flexfuel SIDI engine that is less so designed for any particular octane but more designed to take anything you decide to pour in it, is there any benefit in using 95 or 98? The engine is hopelessly low in torque and 98 does seem to possibly perform better, possibly a placebo effect though.

      BTW My understanding is that since ricers enthusiasts started using E85 and pushing the price up above unleaded it is economically counter-productive to use it due to the reduced energy density. Is this true?

      • pegaxs on 21/08/2018 - 12:22

        I would like to say I know what is causing that, but I am a little lost on what would be causing lower torque from running different fuels, but I'll make some speculation…

        I don't know a hell of a lot about flexifuel vehicles, but it may be tuned in such a way that it's tollerable for different fuels. The problem is that E85 requires a higher compression ratio to make it work at it's best. 91 RON fuels run best in low compression engines. So, to make an engine that runs both, something has to give.

        So, what could be happening is the vehicle is set up to run primarily on E85, so other fuels could cause engine knock and the engine adjusts timing and power to compensate for the lower RON fuels.

        And yes. As for E85, there is no point running it if your car cannot make the most of it. And E85 has much less energy density per litre, but due to its RON, you can jam a lot more into the cylinder. More fuel = bigger bang, and that makes more power at the cost of extra fuel having to be consumed. So, unless you don't care about fuel costs, I wouldn't run E85 in every day driving…

  • RyanMK on 26/07/2018 - 10:27

    On an unrelated topic, how do you find the Levorg? It's a car I've had on my shortlist for a while now.

    • Wampus on 26/07/2018 - 10:37

      I absolutely love it. If I drive it like a nanna I get 8L/100k. If I want to put it through its paces it's such a fun car to drive, not just the power but the upspec suspension and AWD (In the GT-R model).

      Only downside is the CVT, it doesn't come with manual as an option, but I've been pleasantly surprised at the CVT's reaction time.

      TLDR: I wanted bang for buck and I got it. They're not popular cars so get a broker to get one for you on the cheap from dealers wanting to move stock

    • Ugly on 26/07/2018 - 12:47
      +6

      Have you ever noticed that Levorg backwards is Grovel?

      • blitz on 26/07/2018 - 13:55

        "the story goes that the name Subaru came up with as the replacement for its Liberty GT wagon — Levorg — is filled with significant nods to its past. LE stands for “legacy”, VO stands for “revolution” and “RG” stands for “touring”. I couldn't help but notice that Levorg backwards is “grovel”."

        from the Geelong Advertiser

        • Wampus on 26/07/2018 - 14:05
          +1

          Yeah it's the world's worst car name. No wait, Premacy is.

          Grovel = my level of sex appeal

  • Fergy1987 on 26/07/2018 - 10:47
    +3

    The only thing I notice is that my car gets 40 rods to the hogshead on 98 fuel, and that's the way I like it.

    • pegaxs on 26/07/2018 - 11:21

      I get upset if I drop under 4 Gill to the Chain

    • Cartman2530 on 26/07/2018 - 16:24

      Mileage on mine is 1 highway, 0 city.

  • Euphemistic on 26/07/2018 - 10:56

    Come back to us when you can measure the difference is what I reckon.

    Sure, people say they can feel the difference, but I'd bet in a lot of examples their mind is confirming what they think, a well known psychological effect. I've tried different fuels in my cars and not noticed any significant difference measuring fuel economy. I get as much variation tank to tank on the fuel economy with the same fuel as I do with different fuels.

    • psyren89 on 26/07/2018 - 11:18
      +1

      their mind is confirming what they think, a well known psychological effect

      https://en.wikipedia.org/wiki/Confirmation_bias

    • Wampus on 26/07/2018 - 11:19

      Honestly, I suspect in my case it's probably psychological. But still.

      • Euphemistic on 26/07/2018 - 12:24

        Honestly, I suspect in my case it's probably psychological. But still.

        So get some measurements. Otherwise you are wasting money for no tangible benefit.

        • Wampus on 26/07/2018 - 14:07

          The United 98 is about the same price as a lot of places 95 (United don't do 95, or at least my local doesnt)

      • db87 on 28/07/2018 - 11:37

        The subies have been known to be a bit sensitive to the lower octane fuels, especially the EJ series. Even if you don't feel/hear the knock, pulling engine reports will show you that events have happened. End result being a pre-mature end of life for your engine. It might not be about more power as such, but as someone said above, it's the potential to minimise/reduce knock.

    • [Deactivated] on 26/07/2018 - 11:33

      Very true.

      If a car accepts a range of octane, one will not feel the difference especially on everyday drives. The foot will compensate for the power difference.

  • Oz8argain on 26/07/2018 - 11:31

    can you ask your friend if the RS is ok for daily driving and long distance? is the suspension too hard and seat bolstering too aggresive?>

    • Wampus on 27/07/2018 - 09:24

      He used to drive long distances for work, and said it was fine. You're always going to feel the bumps in a car like that but it's the trade off for not driving a wallowing barge

    • ozeebee on 31/07/2018 - 17:55

      The Focus Rs has the exact same Recaros I have on my Megane Rs, and it's so comfortable even on long distances. My only real complaint is that they're quite hard to get in and out of but that's also due to the 2 door format. Maybe it will be a bit better for the Focus.

  • HighAndDry on 26/07/2018 - 12:40

    Can tell a slight difference - I don't think it's enough to justify the price difference though.

  • buckster on 26/07/2018 - 13:15
    +4

    Good question - my car's ECU detects the difference and I found I had increased fuel economy with 98 over 95, but no notable difference in performance.

    The difference in fuel economy actually made it about 0.5cents cheaper to get the 98.

  • No on 26/07/2018 - 13:20

    I always ran my Golf GTI on 98 then decided to try 95 which is what VW recommends. I have only done about 2000km's since switching but haven't noticed any difference in the performance or economy.

    • Wampus on 26/07/2018 - 14:06

      Thats a nice car

  • bobbified on 26/07/2018 - 13:30
    +1

    I get about 10% difference in mileage between regular unleaded and the 98 octane.

    • DarkOz on 27/07/2018 - 08:47
      +1

      This is exactly why we are using 95/98 instead of 91. We get the extra mileage from 95/98.

      95 costs about 10% more than 91 and 98 costs about 15% more than 91. I am happy to gain 10% extra mileage from 98 over 91 because the car runs smoother. Also I am hoping 98 is actually better for the engine as claimed.

  • rompastompa on 26/07/2018 - 13:37

    I put 98, due to being an old car (5.7ltr) . It's probably wrong, but I'm assuming it runs cleaner? So, running it for maintenance rather than performance.

    • Euphemistic on 26/07/2018 - 15:55

      Do you also purchase 2 bottles of Koolaid to get the 4c/l discount when you fill up?

      • rompastompa on 26/07/2018 - 16:02
        +3

        Na, 2x2L of milk :O

    • Wampus on 27/07/2018 - 13:42

      those 351s are such a great engine. I only prefer the small block mopar 360 over them.

      • Euphemistic on 27/07/2018 - 22:59
        +1

        Could be a 350, 351 works out to 5.75 and was usually shown as 5.8.

  • Levathian on 26/07/2018 - 13:41

    My car has a minimum octane of 91 but the recommended octane is 95 (and 95 is the minimum for overseas models). I noticed absolutely no difference between the two.

  • TheBilly on 26/07/2018 - 16:05
    +4

    Only highly tuned vehicles can really make the most of 98

    He is correct on this statement - "Theoretically" and I have outlined this word for the smart assess on here as this is very theoretical with a lot of variables. A higher octane fuel does not increase power with no other change in your engines ignition timing. The octane rating of fuel determines the amount of compression the fuel can withstand without igniting i.e. the higher the octane rating the more compression the fuel can withstand before igniting in essence lengthening the fuel burn within the cylinders chamber. The ignition timing refers to the number of degrees before the spark will ignite the air-fuel mixture in the combustion chamber during the compression stroke of the cylinder. What people do to generate power (by people I mean racing workshops that specialize in track cars, drag cars etc). They retard the ignition timing by causing the spark to occur much later in the stroke so the air-fuel mixture is sitting at a higher compression within the chamber, generating more power. This is not something you would do in a road car as getting it wrong will be expensive and it is only made possible with a higher octane fuel in conjunction with the retarding of ignition timing. So as somebody else posted above, tuning your vehicle for 98 but running 91 is pointless, tuning vehicle for 91 but running 98 is pointless, your tune has to match the octane rating for optimal results. Changing this tune is not something you just do on the fly in the 90's and 2000's it was a process of trial and error and getting the vehicle on a dyno to see how it reacted in terms of power to ignition and octane rating (not sure if modern vehicles do this on the fly nowadays).

  • DarkOz on 27/07/2018 - 08:40

    We used 95/98 not so much for the power but 2 things we noticed. The car runs smoother and the mileage is higher.

    Running smoother is very subjective but the mileage is definitely higher. Although you don't get the extra 10% from 95 over 91 or the extra 5% from 98 over 95.

  • JIMB0 on 27/07/2018 - 09:42
    +14

    Most cars will be quicker on 98 as your wallet will be lighter.

  • Jimmycfc on 27/07/2018 - 11:00

    I wish United petrol stations were still around and they still had the 100 octane, i definitely noticed a difference in that stuff.

  • Bakamonoda on 27/07/2018 - 14:58

    91ron 42l 550kms
    98 Ron 42l 470kms

    99 pulsar. N15.

    Off topic. But use what your engine is designed to.

    • pegaxs on 27/07/2018 - 22:38
      +1

      And this was lab tested, on a dyno, under controlled conditions?

      You could run that same test in a week and get the complete opposite results. But it is refreshing to see that it’s not the typical “I get 150km more per tank from using 98 in my 2003 Camry…” type of comments that usually get posted in these threads.,,

      But spot on with your final comment. Use what your engine and ECU is designed to run on. :)

      • Euphemistic on 27/07/2018 - 23:03
        +1

        Yes, probably drove harder because 98 gives ‘more power’, therefore used more fuel.

        Driving style/conditions makes more difference to economy than fuel type according to my measurements over several years of fills in two different cars.

      • smpantsonfire on 28/07/2018 - 15:53

        If I fill up with 91, and drive with spirit, I get 450 km from a tank. If I fill up with 98, and drive with the same spirit, I get 550.

        Tested over 8 years.

        • pegaxs on 28/07/2018 - 17:30

          Of course you do… ;)

  • cpkk on 28/07/2018 - 07:39

    Thoughts on differences between petrol brands? My butt dyno swears by BP Ultimate

    • [Deactivated] on 21/08/2018 - 10:31

      Apparently it varies from state to state (and, again apparently, in some states all brands are the same fuel) but the consensus from mechanics in the 90s when there were dirty fuel problems fairly often was that BP was the best and Shell the worst.

  • neonlight on 28/07/2018 - 09:32

    My old prelude was better on 95 than 98 and had more mileage. I guess all depends your engine

  • luffyex2010 on 28/07/2018 - 10:02

    I drive a v6 car and i could be wrong.

    98 is better, you can tell when you are driving steep uphill roads, the rpm will maintain, speed seems to consistently go up without stepping on the acceleration pedal too much other than that….your car engine sound can tell you alot if the petrol is suitable for your car.

    Maybe its all just my imagination.

  • ol mate on 29/07/2018 - 09:31
    +2

    Warning: my Ozbargain card may be revoked after this post.

    I can't say I've used 95 a lot (2 cars with 95 min, 1 that was 98 recommended), but the 2 or 3 times that I did, the fuel economy went to sh*t (in the 95 min, 9L/100km to 12L/100km - give or take the same conditions).

    Either way, my logic is that 95 costs you 15c more than 91, whereas 98 only costs 7c more than 95 (so like $3 a tank) so you might as well pay the "top up" between 95 and 98. Works out to be <$100 every 10k km for peace of mind that I won't make the engine ping because of my fuel choice.

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