Premium fuel...................worth it ?

Discussion in 'Bad Dog Cafe' started by Tomm Williams, Feb 13, 2019.

  1. 985plowboy

    985plowboy Tele-Afflicted

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    Maybe you drove more carefully when you had a brand new truck.
    Now that you're used to it you could be driving a bit more, shall we say, confidently.

    Maybe your right foot gained weight.
     
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  2. Chunkocaster

    Chunkocaster Poster Extraordinaire

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    I have noticed that small engines I own don't perform any better on premium fuel but often they don't like it and run better on the standard fuel. These are standard carburettor motors from 5 up to 24 hp. In my car with electronic fuel injection it seems to increase the power a small amount and run a little smoother. If I plan to tow I will fill up with premium fuel, most often I stick to standard for normal driving. As for cost I think it can only be measure over the long term also taking into consideration the possibility that premium might extend the life of your motor if it runs better when using it.
     
    Last edited: Feb 14, 2019
  3. Paul Jenkin

    Paul Jenkin Friend of Leo's

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    I have a 2 litre diesel car and the fuel options, at least in the part of the UK where I live are mostly "standard" or "city diesel" which, supposedly gives a cleaner burn and cleans the injectors a bit.

    I've never noticed any difference in MPG (I average about 38-40 MPG on a mixed cycle and 50 ish MPG when doing a longer, motorway run) from one to the other.

    I've had petrol cars in the past and, whether it was a perceived difference or an actual difference, I don't know, but I did seem to get better pick-up / performance with the higher octane - but I don't recall whether MPG was better or worse.

    What I have found useful is that having the tyres set at the correct psi, keeping the windows closed, not using air-con and accelerating and braking gently / letting the engine gears slow me down has a very positive effect on MPG - maybe as much as a 10% saving.
     
  4. Ignatius

    Ignatius Tele-Afflicted

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    Nope, I check them regularly.
     
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  5. imwjl

    imwjl Poster Extraordinaire

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    I did the total nerd thing on this topic because the farmer's coop a mile away sells gasoline with and without the ethanol and various grades. My current car has semi-autonomous driving features so I know the computer and cameras keep things consistent. Trips to the cabin and a particular work site were the measure.

    No ethanol gasoline was a wash because it cost more. Premium fuel only worked better on trips when the car could get some ping - heavy load or more drag via roof box and bike racks.

    This past summer we did an epic road trip with my wife's modern 292 HP rig. Even with a big load it only seemed like you just want to cut the ping. For one sub-trip that was out and back at high altitude it did seem happier with the non-ethanol gasoline that also cost more.

    I'm just sticking with the cheapest gasoline that doesn't have me hearing ping. I do agree with comments on driving style. I have friends with same car, my wife and daughter share the cars with me. Times I've consumed most of a tank seem to show I burn less fuel. My impatient friends with same car complain about fuel mileage. Yes on tire inflation and the tires. My all weather (have the S snow rating stamped in tread) dropped my fuel economy by almost 1 MPG over the OEM tires.
     
  6. unixfish

    unixfish Poster Extraordinaire

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    Bolded above - and here I thought religion was a no-no! :lol::lol::lol:

    @getbent is right about cleaners. Premium fuel is $0.60 per gallon more than regular unleaded where I live. Premium often has a bit more cleaners than regular. If you see a slight increase for a few tanks, well, it could be the detergents. His point was exactly that - keep the system clean, and you will see the same results.

    Winter time here means ethanol mix. Lower MPG.

    Tire pressures drop in the cold - lower MPG.

    Colder weather - lower MPG.

    Engine not warmed up - lower MPG.

    Warming up engine before leaving - lower MPG.

    Then, introduce some fuel detergents, which minimizes the effects of one or more of the above, and better MPG. Add driving style, traffic, etc - and you have correlated data without causality.

    @Tomm Williams - premium fuel might be giving you better mileage - for now - but there are so many variables involved that I don't think anyone can say it's just the fuel.
     
  7. chris m.

    chris m. Poster Extraordinaire

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    Never try to calculate gas mileage based on movement of the analog gas gauge. The first “half” usually lasts way longer than the second. The accurate way is to fill up, measure miles es, then fill again. The amount required to fill back up is gallons consumed. Modern cars with fancy electronics will give you an instantaneous and average mpg reading. Those are probably fairly accurate but you would need to reset the averaging function when changing fuels to do the comparison.

    I agree that besides lower energy the big problems with ethanol are damage to certain types of plastic and separation when it sits. I have a boat that sits for months at a time and starting it can be a problem when there’s old gasohol in the tank.
     
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  8. boris bubbanov

    boris bubbanov Telefied Ad Free Member

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    The thing about Premium Unleaded is, fewer and fewer cars really need it, and therefore much less of it is sold than previously, and the vendors feel the need to claw back some of their outlay for even providing the customer with the choice of Premium, and so relative to the price of Regular Unleaded the price is just so darned high. And thus in turn even more people stop using it and on the cycle goes.

    IMO what this then means is, Premium is seldom going to be fresher fuel than is the Regular. And old gasoline is not good. Except sometimes when the refiners switch from Winter blend to Summer or vice versa, and the weather doesn't follow the refiner's plans, you can find weeks old Premium that's better suited to whichever non hot or non cold weather you find yourself in.
     
  9. beninma

    beninma Friend of Leo's Silver Supporter

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    It is totally normal and expected to get lower fuel economy in the winter. Absolutely no mystery about.

    Fuel is sold by volume, not mass, and the density of the fuel does increase a little at cold temps.

    But that is not nearly enough to make up for the change in temperature, which affects the air density considerably more than the fuel density. Your cars fuel injection system and/or carb (depends on how sophisticated the carb is) automatically uses more fuel to keep the mixture consistent as the air density increases. Higher mass of air = higher mass of fuel to keep the same mixture = more horsepower/torque = lower fuel economy.

    There can be little effects that can mitigate this like you using less throttle as you don't need it but there are a bunch of other things like increased rolling resistance in your tires and increased drag on the car (from increased air density) that all work to drag down fuel economy in the winter.

    This is the same thing as why diesel fuel economy is not all it's cracked up to be too... diesel always has higher density than normal gasoline.. you are putting more fuel if measured in mass in your tank. If we were measuring "Miles per gram" or "Miles per pound" instead of "Miles per gallon" or "liters/ X Km" the gap between diesel and gasoline engines would be smaller.

    The whole thing with octane (premium) is indeed just knock resistance.

    I think it's all tied in with pollution but it's pretty interesting we're arguing about 91 or 93 when fuel as high as 150 octane was around in the 1940s for military and racing applications.
     
  10. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    Right, so your engine essentially detunes itself when run on lower octane fuel that will detonate with the engine running at the designed tuning specs.

    It would likely be the ignition system retarding the timing, more than the fuel system sophistication, but I'm not sure what that particular engines computer is adjusting.

    What cheaper gas does is (possibly/ worst case) explode prematurely from compression and heat before the spark plug fires. While many (not you) say better gas isn't really better, that would be incorrect if an engineer is tuning an engine for high efficiency, which is required for both performance and fuel economy.
    Gas that ignites on its own when the piston is still on the compression stroke is worse gas.
    Gas that burns so unevenly that the combustion cycle is jarring rather than smooth, if it doesn't ignite before the plug fires, but knocks anyhow because it doesn't burn smoothly, is worse gas.
    Better gas burns smoothly and evenly.
    The combustion/ power stroke is the most stressful event in an engines cycle, and if the fuel burns evenly it does less damage. You want the fuel to burn and expand for a good portion of the stroke, not all at the top. There is actually a sort of weather pattern in the combustion chamber, and the engineers shape the intake runners, valve angles and combustion chamber to create a wind pattern that ensures smooth and complete combustion over as much of the power stroke as possible. This involves a small portion of the fuel burning at first, them more of the fuel ignites as the piston moved down, and finally the last of the fuel mixture burns at the lower portion of the stroke.
    This is like a car pushing your car as opposed to hitting your car, which is essentially what low octane gas does when it burns quickly and unevenly. Hits the piston rather than pushing it. If you look at pistons and combustion chambers damaged by too low octane, you will see smashed pistons and burned away valve seats, as well as warped heads and possibly even cracked blocks.

    The combustion event, if slowed down for analysis, is actually slower than the engines combustion stroke. This is why the spark plug fires before the piston reaches the top, and is advanced even further at higher RPM.
    At low RPM the plug fires a little before the piston finishes the compression stroke, while the piston is still on its way up.
    At higher RPM the plug fires even sooner, with the piston even lower in the compression stroke, because while the engine is moving faster, the combustion event cannot speed up.
    So the engineers design and build in a good lead for the start of combustion, in order to have the pressure start pushing the piston down at exactly the right time, no matter what the engine speed.

    For operators to bypass the engineers by assuming that everything is fine as long as they don't hear the rattle of detonation is pretty much ignoring the tech involved in engine design. Of course we do have that right, and modern engineers design in failsafes for operator error. Then the manual writers let us know that regular gas won't kill the engine or void the warranty, even though the engine was designed to run on higher octane.

    A modern engine can retard itself (retard the timing) if given the wrong (lower octane) gas by the operator.
    But that doesn't mean expensive gas isn't better gas.
    And it doesn't mean the retarded engine is running well.

    OTOH, an old time engine with distributor, mechanical advance, and vacuum (retard) advance, will not benefit from better gas if tuned to operate without detonating on regular gas. You need to physically advance the timing in order to get the benefits of premium, which generally involved loosening the distributor housing and rotating it a few more degrees advanced.

    Knowing all this, I still put regular in my Volvo five cylinder turbo, because 1) I'm cheap, and 2) it's not really a high performance engine at 195hp/ 2.5L.
    I'm not really sure if the engineers designed it to run optimally, or moderately, since it's more of a family car than a luxury performance car.
    They do make a higher pressure turbo version, which will also survive 87 octane but really is designed around high performance.
     
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  11. Guitarzan

    Guitarzan Poster Extraordinaire

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    My late 80s F-150 with an inline 6 would knock and ping a bit on 87 octane. The higher octane fuel did not have any pre-ignition/detonation or run-on. If those things are absent, fuel will be consumed more efficiently. Then there is the question of carbon build up on cylinder heads.

    Since you are in it and curious, there are a couple of things that might interest you. One is that you might consider running a couple of bottles of Seafoam through 2 tanks of 87 octane and then run 87 without additives and see what results.

    You might also test octane booster additive and run the numbers to see if it is cheaper than buying higher grade and whether it produces better results than the straight 87 octane.
     
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  12. Guitarzan

    Guitarzan Poster Extraordinaire

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    BTW, I run Seafoam in mine about every other week.

    I also like to run a tank of ethanol free gas (which also has higher octane) through about once a month.

    I've driven the truck a long time and know it, and I believe it helps.
     
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  13. chris m.

    chris m. Poster Extraordinaire

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    Just getting an engine running steady at higher RPM helps clean out carbon buildup and reduces potential for knocking and other problems.
    Lots of idling and cold starts will do the opposite-- promote carbon build up. Modern detergents like Techron can really help prevent these
    issues and optimize performance. It is not uncommon for cars that normally should not require premium to start eventually knocking and need it.
    This is usually a result of carbon buildup. The preferred solution is to actually eliminate the carbon buildup rather than treat the symptom
    by using premium.

    High compression engines that call for premium is a different story.
     
  14. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    I ran some seafoam through the snowblower this fall because I never got any stabil for the gas last winter. Couldn't find any stabil on the shelves at my local places, and the snow stopped last winter long before I'd gone through my first jug of gas.
    I was pretty worried that the snowblower might not start (or just run poorly) due to no stabil, and being stuck with only ethanol gas in Maine.
    But gas I'd bought a full year prior hadn't caused any problems, started fine and ran smooth even before the seafoam could have made it into the bowl.
    I have a Honda lawnmower I got free with a clogged carb, and a Husqvarna weedwacker I bought new that clogged even with stabil in the gas because it was two years on one gallon in the can. Actually with the Husquvarna it idles but the main jet seems clogged.
    Ran another dump sourced lawnmower the year before last and an electric from work last summer, but I gotta get the Honda going for the coming grass season.

    Can seafoam replace a carb rebuild?
    A friend says he gets clogged carbs working with seafoam, but IDK how it gets through the carb if jets or the needle is clogged.
    The Honda is in really clean condition and has good spark, but won't catch at all.
     
  15. PCollen

    PCollen Friend of Leo's

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    Use what your owners manual recommends. But buy a good brand, not some of this low end discount stuff. I get better mileage using Cumberland Farms gas than I do using Sam's of same octane rating, maybe do to a difference in the additives each contain. I also like to buy from newer locations because their tanks are likely cleaner than those which have had gas sitting in them for decades..like never rinsing out your coffee pot .
     
  16. Blrfl

    Blrfl Tele-Holic

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    This is a really important point because the engine is designed around the fuel behaving a certain way. If the system has to compensate for the behavior of the fuel, the burn isn't going to be ideal and the engine won't do the best job it can converting energy in the fuel to energy at the crank.

    My brother, who was one of those engineers, grouses at people who do that: "some poor engineer spent days slaving over a hot drawing board to figure this stuff out, those bozos didn't." The first I ever heard him use it was in reference to people who cut down their coil springs, but it applies here, too. I have ties to the high-performance computing community, and there's a huge number of compute cycles expended simulating the behavior of fuel in combustion chambers.

    People also don't understand that there has to be a certain amount of detonation for the fuel system to sense it and compensate. That's better than full-time pinging, but each time inflicts a little more damage.
     
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  17. Marc Morfei

    Marc Morfei Tele-Afflicted

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    Ha, I would take that. My wife drives 90 miles an hour and tailgates like 6 inches off the bumper of the car in front of her. And she insists she gets carsick as a passenger so she always needs to be the driver.
     
  18. Blrfl

    Blrfl Tele-Holic

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    (Sorry, two quotes in a row.)

    Seafoam is great stuff, as is Techron. I use Seafoam in my motorcycle to prevent a problem of build-up on the valve seats common to that model, and for that, it helps. Just don't judge the way your engine runs while you've got it in your tank, because I'd swear it burns better than gasoline. :)

    If the system is so clogged up that it can't pass enough fuel to run the engine, you're going to have to go in and clean it by hand.
     
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  19. WetBandit

    WetBandit Friend of Leo's

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    Retarding timing can only go so far before it, itself becomes and issue.


    Check this puppy out!

    Just done some final assembly, currently sitting in my floor. Wonder how many mpg she will afford?


    intake.jpg
     
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  20. telemnemonics

    telemnemonics Doctor of Teleocity Ad Free Member

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    Wow, that is truly awesome!
    I just moved a pile of Holleys and parts out of my garage so the guy buying my car won't try to take them in the deal.
    I left a 750 vacuum but took a 750dp and an 830 annular.
    Plus a bunch of bowls blocks and spare parts.

    Who welded up that manifold?
     
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