Better Fuel Economy Suggestion for All Cars

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Sarasota, Florida
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Needing a long SUV for my projects and wanting some luxury for "once" I purchased the new Black Label Lincoln Navigator. I got the extended version the first of May this year. According to their web site: Capable of producing 450 horsepower* and 510 lb.-ft. of torque,* the twin-turbocharged 3.5L engine in the Navigator** is a true powerhouse. *Horsepower and torque ratings based on premium fuel per SAE J1349® standard. Your results may vary. **Vehicle shown available at participating Lincoln Black Label Dealers only. I saw the 0-60 times in as little as 5.5 seconds - attractive for this sports car enthusiast. Note however that these figures assume you are using Premium Fuel. You can use Regular fuel or E85 fuel as well. The truck is around 6 months old now with around 4,000 miles. Lincoln does free service for the first 4 years, oil changes every 10,000 miles or 1 year intervals. It uses Motorcraft 5-30 fully synthetic oil. It does not get as hot here in Florida as in other places around the country and we do not have any mountains. I never tow anything and never drive over 80 MPH. As such I will be using 5-20 or 0-20 motor oils. As with some others here I could not stand to go 10,000 miles on a single oil change. I chose to put in 5-20 Mortorcraft oil at the 3,000 mile mark. I was hoping to maybe get a little better fuel economy. No change. It could be that the break-in oil was a 20 grade and that could explain why there was no change. Or there is just not much of a difference as is sometimes the case. If the fuel economy goes down a little after the scheduled change into 5-30 at the dealership in 6 months then we will know the effect of viscosity on my fuel economy. I predict there will be no difference. I did some experiments with fuel grades in the milage range of 2,500 to 3,000 miles, before the first oil change. Originally I used only premium fuel, mostly Shell. I got 20.5 MPG during this period in my mundane around town driving. I then almost emptied the fuel tank, ran one full tank of Regular gas and then got another tank of Regular and started MPG records again. In fact I have been using only Regular gas since then. Eventually I hit 3,000 miles, changed the oil to a "thinner" one and still had no change in fuel economy. The new readings were 19.5 MPG before and after the oil change. So I get 5 percent better fuel economy (1 MPG) by using Premium instead of Regular fuel. Even though premium fuels cost more than 5 percent more than regular fuels I will be using it to better the environment by this amount. I have never found that using a 20 grade vs a 30 grade oil made any noticable difference in fuel economy in my cars. But this is a significant difference by using differenct octane fuels. It occurred to me that we should be using Premium fuel in all cars to get this significant improvement in fuel economy. Maybe we should up the octane of Premium Fuels even higher. Could we get a 5-10 percent better fuel economy rating? Obviously we would have to produce new engines with the necessary timing advancement but we could also retroactively adjust all cars one way or another to take this advantage. Maybe having only one grade of fuel at the station would help reduce its cost making it worth it for the Increased milage. What say you? AEHaas
 
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NH
I've read somewhere that many OEM's want to go down that path and make their engines use only premium, presumably for the same reasons you mention (better mpg, more power). Personally I wouldn't care too much, I mean, if the mpg increase was greater than the increase in fuel cost, then it's a net win for me. It's when it's not that I have second thoughts. Too bad we couldn't get cars with two fuel tanks, or at least a tank with high octane fuel in it (maybe just a few gallons of something on the other side of 100 octane). That way, for mundane driving, a lower octane fuel could be used, where the extra isn't needed. Under power some of the high octane fuel could be pulled in and mixed in. But I'm guessing what the OEM's are finding is that even at part throttle high octane is required as they are getting some high pressures even at low power output. So that idea probably doesn't work. Finally... a Prius will handily beat CO2 and other emissions compared to your SUV. That's a rude thing to say I know, and not of any help to someone who has a big family or needs to haul around lots of stuff. I'm no more anti-big-SUV than I am anti-Prius. But if mpg is a concern then quite often a smaller car will obtain a smaller carbon footprint. Not just on fuel but also in tires, used oil and whatnot. In some ways I wonder if multi-vehicle ownership isn't the way for us to look at in the future. Many of us can afford to have more than one vehicle; maybe one big one and one small one would do us well. That is what I've done, a commuter that I put my miles onto, and a big do-all vehicle that gets few miles due to fuel burn.
 
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Lakeside, CA
That's not how it works. Just because you got better mileage in your vehicles does not mean others will too. Higher octane fuel is not the solution.
 

Kestas

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5%-10% better fuel economy with premium.... which costs 30% more? No thanks. What is your definition of "fuel economy?" The name of the game isn't highest mpg, it's lowest fuel cost per mile. Premium doesn't provide that.
 
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Wisconsin
Originally Posted by Blkstanger
That's not how it works. Just because you got better mileage in your vehicles does not mean others will too. Higher octane fuel is not the solution.
This is sort of like saving money on a hybrid or EV, TCO is terrible because you pay thousands more up front then hundreds extra of taxes every year which wrecks any savings potential

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Canada
The reason you get better mileage with your TGDI with 91 and up octane is because your engine is tuned for this fuel. It can lower performance/mileage by retarding timing and other thing because it will detect knock from the knock sensor (lower quality fuel) but is not the best for your engine. Putting 91 octane fuel in a regular NA engines tuned for 87 octane will not see ANY improvement mileage-wise.
 
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6,683
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California
Originally Posted by jbutch
Putting 91 octane fuel in a regular NA engines tuned for 87 octane will not see ANY improvement mileage-wise.
Toyota words the owner's manual of their V6 models that while 87 octane is fine for everyday use, premium is suggested to realize the best performance out of the engine. Premium isn't recommended for a Prius - it burns slower which may encourage combustion chamber and valve deposits which might result in delayed start/no crank DTCs. I caught the parents trying to cheap out on fuel with their LS430 by using regular and adding in a bottle of Techron but I told them it's not the additives, it's the octane and you will be burning more gas than you "saved" and maybe causing long-term issues. I warned them if you want to cheap out, I'd rather you use Arco or no-name premium.
 
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MA
Originally Posted by Rmay635703
Originally Posted by Blkstanger
That's not how it works. Just because you got better mileage in your vehicles does not mean others will too. Higher octane fuel is not the solution.
This is sort of like saving money on a hybrid or EV, TCO is terrible because you pay thousands more up front then hundreds extra of taxes every year which wrecks any savings potential
Wow, that's a really big spread between regular and premium. The mid grade is a real money maker though, should be half of regular and half of premium so it should be $3.25 instead of $3.70. So they make an extra 45 cents per gallon. As for the OP, 3k oil changes are somewhat extreme. I used to do 5k oil changes on semi synthetic and got over 200k on a Ford Taurus. Would go up to 7 or 8k once in a while when I didn't have time to change it. Doing 3k oil changes is just a waste of oil and bad for the environment, a large percentage of oil doesn't get recycled. I do 10k oil changes now on my Mercedes which is what it calls for. It has an 8.5 quart sump so I figure it doesn't get used up as much as a car that only does 4 or 5.
 
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Vancouver
OEM's have actually been pushing for 91 to become regular fuel for quite some time. They believe they can really increase both mileage and power if that was the case. I'm all for it if they can leave the "regular" prices as they are now and just eliminate 87 and 89 altogether. Maybe have 91 as regular and 93 or 94 as premium.
 
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Austin, TX MSA
I would be curious to see the results of ethanol free 87 vs. regular E10 87. They have no-ethanol 87 at Walmarts around here. It costs more than premium, but, could be an interesting experiment. As it is, I use the ethanol free fuel in all my OPE. Starts right up after sitting for a couple of months.
 
Originally Posted by Jimmy_Russells
OEM's have actually been pushing for 91 to become regular fuel for quite some time. They believe they can really increase both mileage and power if that was the case. I'm all for it if they can leave the "regular" prices as they are now and just eliminate 87 and 89 altogether. Maybe have 91 as regular and 93 or 94 as premium.
If the cheaters hadn't ruined diesel for everyone, we'd be going down a much better path for MPGs. Not only does diesel contain a significantly higher energy per volume than gasoline, but you can also "refine" approximately 25% of crude oil into usable diesel just by heating it up to about 900*F and removing the lighter fractions. There's other stuff that goes on I'm sure (I'm not a refinery chemist, but I did stay at a Holiday Inn Express last month) but that's how it was told to me when I was working at Citgo & BP refineries in IL. Plus, with compression ignition, there is no LSPI, no detonation, unlimited boost potential within the limits of the block/head architecture, and others. But you'll also need biocides, anti-gel chemistry, and water removal as well. I think the biggest pitch "for" diesels is this: Americans are drawn to buy a vehicle with high horsepower ratings, but unconciously enjoy driving high torque engines. They just feel more responsive and snappy, and are much more usable than something with [email protected]
 
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It's all about compression, which is why they want higher octane as standard. More compression is virtually always better in terms of power and economy and therefore more efficiency.
 
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British Columbia, Canada
Hello Dr Haas, You'd have to do quite a few test tanks to be sure that there really is an increase in mileage. If you're getting better mileage it could be because your vehicle is set up for it, though most vehicles are not. In Canada premium (RON 91) gasoline is generally ethanol free, whereas regular (RON 87) gasoline has up to 10% ethanol. You will get better mileage without ethanol and the absence of ethanol alone would explain better mileage. According to an article I read some years ago, ethanol made from corn isn't really better for the environment as there is so much fuel used in producing it. We have corn based ethanol added to gasoline in Canada too but it seems it's mostly a feel good issue. And the farm lobby likes it too. Finally, it used to be said that premium fuel required 10% more crude oil base-stock to produce. But that was a long time ago and I don't know the current situation. It seems likely that it requires more at least. All in all, I'm not convinced about premium fuel being "better for the environment".
 
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SW Louisiana
So I get 5 percent better fuel economy (1 MPG) by using Premium instead of Regular fuel. Even though premium fuels cost more than 5 percent more than regular fuels I will be using it to better the environment by this amount. So your trying to better the environment by driving a Navigator and doing 3K mile oil changes??? Dude, if you can afford a Navigator, put 93 octane gas in it and run the recommended 5W30 oil down to 20% or so on the OLM and you and the ecoboost live happily ever after.
 
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Kestas

Staff member
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13,723
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The Motor City
Originally Posted by Jimmy_Russells
OEM's have actually been pushing for 91 to become regular fuel for quite some time. They believe they can really increase both mileage and power if that was the case. I'm all for it if they can leave the "regular" prices as they are now and just eliminate 87 and 89 altogether. Maybe have 91 as regular and 93 or 94 as premium.
OEMs have been pushing this in order to help meet CAFE standards while maintaining horsepower. All this at the expense of your pocketbook because premium costs 30% more than regular. America has lost focus with the almighty one-track CAFE standard, when we should be aiming for the least cost per mile traveled.
 
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My experience has shown better fuel economy with running 91-92 octane premium. The difference is about 1.5 to 2 mpg. This is on a Mazda SkyActiv 2.5 naturally aspirated engine which has 13:1 compression. In addition, response and power, especially going up hills is better with the premium. It might cost me more but with everything I've observed I will stay the course.
 
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Arizona
Originally Posted by Kestas
OEMs have been pushing this in order to help meet CAFE standards while maintaining horsepower. All this at the expense of your pocketbook because premium costs 30% more than regular. America has lost focus with the almighty one-track CAFE standard, when we should be aiming for the least cost per mile traveled.
Not necessarily. If you actually increase compression ratios and thus improve energy extraction (thermal efficiency), the trade needn't be nearly so bad as you imply. Your rationale argues for bringing the high-altitude 85 AKI regular (or lower) to the rest of the continent simply because it's cheaper to buy at the pump.
 
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Ontario, Canada
Originally Posted by PimTac
My experience has shown better fuel economy with running 91-92 octane premium. The difference is about 1.5 to 2 mpg. This is on a Mazda SkyActiv 2.5 naturally aspirated engine which has 13:1 compression. In addition, response and power, especially going up hills is better with the premium. It might cost me more but with everything I've observed I will stay the course.
Yes, typically engines with higher compression will benefit. Our 5.7L "requires" 87 at minimum, but recommends 89. Since Costco only carries 87 and 91, it gets 91. The CR on it is 10.5:1.
 
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