 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / General Car Topics / November 2007Does Premium Provide Better Fuel Economy? - My Experiences
I have a 2006 Nissan Frontier 4WD V6 Automatic King Cab Truck. The owner's manual has the following to say about fuel: For 4.0L engine. Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91). For improved vehicle performance, NISSAN recommends the use of unleaded premium gasoline with an octane rating of at least 91 AKI number (Research octane number 96). For the first year and 30K miles I used nothing but regular. I keep detailed gas purchase records and has as been my experience in the past, the fuel economy gradually increased as the engine was broken in. After the fuel economy stabilized, I decided to do a comparison test between regular and premium fuel. I alternated regular and premium fuel for extended periods (5251 miles of regular, 2174 of premium, 5150 of regular, 2916 of premium, 926 of regular). I did not include the transition tanks of gas in the miles or gas usage. Total mileage on regular was 11,327. Total mileage on premium was 5,090. Average fuel economy on regular was 19.4. Average fuel economy on premium was 19.8. I never detected any difference in performance. I'd say that it is certain that the use of premium resulted in a detectable increase in fuel economy - something in the 1% to 3% range. Since premium fuel cost 5% to 8% more than regular, it seems that the use of premium is not justifiable on economic grounds. Plus fuel cost only 2% to 4% more, so I may experiment with plus fuel to see if it yields similar fuel mileage increases. Ed > I have a 2006 Nissan Frontier 4WD V6 Automatic King Cab Truck. The owner's > manual has the following to say about fuel: [quoted text clipped - 24 lines] > > Ed It's possible. Some engines will listen for any signs of knock and retard the timing when they hear it, if the engine would normally knock with regular gas when you put premium in it it's less likely to knock so the computer will advance the timing. With the more advanced timing you are getting a bit more power out of the same amount of gas, and assuming your driving habits don't change your gas mileage should improve slightly. Jeff DeWitt > I have a 2006 Nissan Frontier 4WD V6 Automatic King Cab Truck. The owner's > manual has the following to say about fuel: [quoted text clipped - 24 lines] > > Ed This is quite informative and very useful. I appreciate the experiment. But, (<----you knew that was coming:)) here's why I would take that result with a grain of salt. The Nissan Frontier is a truck. It's AWD. Both these factors contribute significantly to the notion that the vehicle wasn't really built with fuel economy as its foremast character appeal, so to speak. In other words, the gearing was chosen to scale hills and large tow capacity, among other things. Aerodynamics is not something trucks do well. AWD also contributes to hurting feul economy because of gearing again, and frictional losses from all those turning drivetrain components. And weight. So, it would follow that switching to the better feul will improve fuel economy, but not by much. Another example: A Nissan 350Z and an Infinit FX35 stopped at a traffic light. They both have the same engine, the venerable VQ35DE V6. The light turns green and they both take off. Who would win? the 350 of course. Much less weight AND better gearing. If the 350 owner went through the exercise of changing fuel types, they'd see a better improvement. Probably the most dramatic improvement would come from a FWD vehicle like the Altima V6 or Maxima. Least amount of drivetrain loss. CD > This is quite informative and very useful. I appreciate the > experiment. But, (<----you knew that was coming:)) here's why I [quoted text clipped - 29 lines] > > CD I would expect a similar percentage improvement, assuming the engines were tuned the same initially. However, it should be pointed out that the 350Z, Maxima, V-6 Altima and FX35 all require premium fuel, whereas the Frontier only "requires" regular (but the owner's guide claims better performance on plus). So it seems likely to me that for the "car" applications the engines have been tuned to provide the best possible performance/economy when using premium fuel and that using regular might actually result in significantly downgraded economy. My Nissan has never knocked on regular and I can't really tell any difference in performance. However, the difference in fuel economy is measurable, even with my crude methods. I have tried this same experiment in the past with a Ford Expedition and a Ford Mustang. The Expedition had knock sensors and it was alleged that the performance and economy would improve if premium fuel was used. That was not my experience. I could detect no mileage improvement when using premium. The Mustang did not have a knock sensor and, as expected, using premium had no measurable effect on fuel economy. Ed On Oct 25, 9:41 am, "C. E. White" <cewhi...@removemindspring.com> wrote: > > This is quite informative and very useful. I appreciate the > > experiment. But, (<----you knew that was coming:)) here's why I [quoted text clipped - 51 lines] > > Ed The Altima V6 and Maxima can run on regular, same recommendation as your Frontier. For the 350Z and FX, perhaps not. So with the Maxima and Altima V6 I still believe the differences would be greater. Now, as for knock, a car's tendency to knock is a function of where it lives. The closer you live to sea level, the more likely your are to knock on a lower grade fuel. If you live in NYC, sea level, use premium, 91 octane or better. Because of the denser air at sea level, the engine WILL use it. If you live in Colorodo, some points which are 4000 ft above sea level, you can happily get away with 87 octane. The less dense air significantly reduces a car's octane needs. CD > The Altima V6 and Maxima can run on regular, same recommendation as > your Frontier. For the 350Z and FX, perhaps not. So with the Maxima > and Altima V6 I still believe the differences would be greater. I am sure the Maxima and Altima V6 "can" run on regular. However, starting in 2007 premium fuel was recommended. Here is the statement from the Altima Manual: For 3.5L engine NISSAN recommends the use of premium unleaded gasoline with an octane rating of at least 91 AKI (Anti-Knock Index) number (Research octane number 96). If unleaded premium gasoline is not available, you may use unleaded regular gasoline with an octane rating of at least 87 AKI number (Research octane number 91), but you may notice a decrease in performance. For the Frontier regular is explicitly recommended. Here is the statement from the Frontier manual: For 4.0L engine. Use unleaded regular gasoline with an octane rating of at least 87 AKI (Anti-Knock Index) number (Research octane number 91). For improved vehicle performance, NISSAN recommends the use of unleaded premium gasoline with an octane rating of at least 91 AKI number (Research octane number 96). I assume if Nissan tells people to use premium, Nissan tunes the cars to get the best advantage from it. For the truck, since they explicitly recommend regular, I assume Nissan tuned the engine to run on well on regular. > Now, as for knock, a car's tendency to knock is a function of where it > lives. The closer you live to sea level, the more likely your are to [quoted text clipped - 3 lines] > are 4000 ft above sea level, you can happily get away with 87 octane. > The less dense air significantly reduces a car's octane needs. Most of my driving is between 14 ft and 500 feet. Ed >>The Altima V6 and Maxima can run on regular, same recommendation as >>your Frontier. For the 350Z and FX, perhaps not. So with the Maxima [quoted text clipped - 35 lines] > > Ed This tends to support my point more, that the Maxima and Altima V6 will show better improvements in gas mileage with 91 or better octane. Like you said, your Frontier may be optimal with 87. Interestingly, my friend has a 93 Maxima with the SOHC V6, not the DOHC in the SE. His manual even says that performance will improve if you use 91. The only thing that could vary on that motor is ignition timing. Everything else is fixed. The 2007 Maxima and Altima V6 has variable valve and ignition timing, so the computer has more parameters to adjust to better take advantage of the fuel it's using over a wider RPM band. I gather that your Frontier motor is configured in a similar fashion to the 93 Maxima V6 motor. CD >On Oct 25, 9:41 am, "C. E. White" <cewhi...@removemindspring.com> >wrote: [quoted text clipped - 68 lines] > >CD This leads to another related question. These experiments prove that premium may have a slight improvement in MPG, and as explained is because the advance in timing. But lets say a person uses regular with 10% ethanol. (PLUS regular) I'd have to check the pump, but I believe that I normally see regular at 87octane and the PLUS at 89 octane. We have increased the octane, thus less knock, and possibly more advanced timing. This this should increase the MPG slightly. BUT I know that ethanol (all alcohol fuels) contain less BTU energy per gallon than gas. I have heard that the E85 drops MPG over gas. Of course that's 85% alcohol, VS 10%. Yet, even 10% alcohol should slightly decrease the MPG due to a slight lower amount of BTU energy. Yet, the octane is increased, so less knocking. This leaves me asking if these balance out each other, or is there a small increase or decrease in MPG? Does anyone know? My driving habits vary too much to use my vehicles to check. I drive on rural gravel roads quite often, then take highways. I drive a truck that may be empty or have a ton or more of hay or other stuff in it. I know that to preform an accurate test, all variables need to be the same, which in the real worls is hard to maintain. Thus they have these testing places that have specific roads, weather conditions, and the cars have their tire pressure checked daily, use the exact same oil, and save driving methods, etc.... Yet, the test from the OP, if he drives the same manner pretty much regularly, does not haul large loads, and other changes, does say something...... I just got rid of my old farm truck, a 1979 Ford F150. Besides falling apart, it sucked gas like crazy with it's large 400 engine, and automatic transmission that seemed to slip till the truck warmed up. I am not the most accurate about watching my milage and gas use, but I estimated I got about 8 MPG when empty, but dropped to 5 to 6 MPG when filled with a heavy load of hay. Even worse when pulling a livestock trailer. > ..... > Yet, the test from the OP, if he drives the same manner pretty much > regularly, does not haul large loads, and other changes, does say > something...... > >........ I'm not sure what you're asking but what I'm trying to say is that C.E. white's experiment should not generally apply to all Nissans. The differenece between a Maxima running 87 or 93 octane will be greater than the Frotntier because the Maxima has a more sophisticated motor to better take advantage of the higher octane. So the Max would show a better improvement in gas mileagerunning 93 octane like he did in his experiment. Given that you have a truck like Mr. White then I would expect your results to be similar. The main varables are in the motor. All cars have variable ignition timing, but there's 2 types 1. Variable ignition timing on a distributor based car 2. Variable ignition timing on a distributorless car 3. With the Maxima add variable valve timing. The difference between 1 and 2 is that ignition timing can only be adjusted to the physical limitations of the distributor. A distributorless ignition can have its timing adjusted through a far greater range. The ECU can play with the timing much more to maximize power. The Frontier which i beleive has variable ignition timing on a distributor will make less of a difference with the octane change than a Maxima which has variable ignition timing on a Nissan's direct ignition system AND varable valve timing. CD > The Frontier which i beleive has variable ignition timing on a distributor > will make less of a difference with the octane change than a Maxima which > has variable ignition timing on a Nissan's direct ignition system AND > varable valve timing. Actually the Fontier has both the direct ignition system and variable valve timing like the Maxima. I think your assumption that the engine management system is less sophiticated than the Maxima's is wrong. It is certainly tuned differently, but I am not sure you can make all the leaps you seem to be making. I do agree that since the Maxima (and Altima V-6) require 91 octane fuel, it seems to me it is likely using regular will result in a greater decrease in fuel economy than for the Frontier. Ed > > The Frontier which i beleive has variable ignition timing on a distributor > > will make less of a difference with the octane change than a Maxima which [quoted text clipped - 10 lines] > > Ed I know the specs on the 2007 and 08 Frontiers engines, but wasn't sure about the 06. That's why I said I believe. It was a guess which means it could go right or wrong. I'm glad you now see what I was saying, that the Maxima and Altima will show a better improvement if someone did your feul economy/octane exercise. CD > I'm glad you now see what I was saying, that the Maxima and Altima > will show a better improvement if someone did your feul economy/octane > exercise. Although I agree with you on this, I don't think we are coming at it from exactly the same angle. I agree that the change in fuel mileage when using regular vs. premium will be greater in the case of the Maxima and Altima than for the Frontier because the Maxima and Altima engines "require" premium fuel. This implies to me that they were tuned for premium fuel. Part of the tuning is the compression ratio. The Maxima engine has a 10.3:1 compression ratio, the Frontier V6 is only 9.7:1. Because of the higher compression ratio, running the Maxima engine on regular will require significant changes in the timing and probably a less favorable intake cam advance. If the Maxima engine had been designed to run on regular like the Frontier engine, I would expect a similar percentage change in economy if premium was used instead regular. However, since the engine was optimized for premium running regular would force unfavorable operating parameters and significantly worse fuel economy. Ed > I know that ethanol (all alcohol fuels) contain less BTU > energy per gallon than gas. I have heard that the E85 drops [quoted text clipped - 5 lines] > This leaves me asking if these balance out each other, or is > there a small increase or decrease in MPG? Does anyone know? My experience here in Australia is that the the increase in octane number from the addition of 10% ethanol exactly balances out the effect of the reduction in energy content. This is the case for my Nissan with knock sensor equipped GA16DE engine. A friend with a 2006 Honda CRV (with a knock sensor) has also found no measurable difference in fuel consumption between our standard unleaded and E10. Both of us record every drop of fuel added to the tank, and milage at every filling, and run spreadsheets to calculate both short and long term changes in economy. Our E10 is 3¢/litre cheaper than regular unleaded and slightly higher octane (due to the addition of ethanol), so for us the fuel choice is clear. John >My experience here in Australia is that the the increase in >octane number from the addition of 10% ethanol exactly balances [quoted text clipped - 3 lines] >found no measurable difference in fuel consumption between our >standard unleaded and E10. In the USA, the figures I saw were a 6% typical decrease in MPG for the now standard 10% Ethanol. Ethanol does produce less power per gallon and you will get poorer mileage. YMMV. But, the octane difference is irrelevant since they in the states I've been in since you don't get a choice. That is, you can't choose Ethanol or not and play octane levels. You buy gasoline at a stated octane level with a stated ethanol level. For the consumer, Ethanol is a net loser since the price per gallon did not decrease when it was introduced and the same gallon of gas now gets you 6% worse mileage. > The Altima V6 and Maxima can run on regular, same recommendation as > your Frontier. For the 350Z and FX, perhaps not. So with the Maxima > and Altima V6 I still believe the differences would be greater. My Maxima runs like crap on 87. The difference between 87 and 93 octane in that car is astonishing. It's like the difference between driving a Taurus and, well, a Maxima. >>The Altima V6 and Maxima can run on regular, same recommendation as >>your Frontier. For the 350Z and FX, perhaps not. So with the Maxima [quoted text clipped - 3 lines] > octane in that car is astonishing. It's like the difference between > driving a Taurus and, well, a Maxima. Same here. My 98 Maxima just hated 87 octane. Living at sea level and my driving habits were a factor. If I had 87 octane in the car, the moment I tried to get some decent power out of the car, ping city, then the ECU retarded the timing quickly, so no more pings, but also no more power. CD > My Maxima runs like crap on 87. The difference between 87 and 93 > octane in that car is astonishing. It's like the difference between > driving a Taurus and, well, a Maxima. Not surprising, that's a huge difference in octane. If your engine has significant carbon the higher octane will be more benificial. > For improved vehicle performance, NISSAN recommends the use of unleaded > premium gasoline with an octane rating of at least 91 AKI number (Research > octane number 96). If your engine has a high enough compression ratio to gain from it. NISSAN said it with their statement. IMO you wouldn't notice the small performance difference. I dragged the same out of Toyota regarding their V6 in the Rav and Camry. The sad part of it is Toyota admitted the EPA ratings require premium fuel, yet regular fuel is stated as the requirement. >>For improved vehicle performance, NISSAN recommends the use of unleaded >>premium gasoline with an octane rating of at least 91 AKI number (Research [quoted text clipped - 3 lines] > NISSAN said it with their statement. > IMO you wouldn't notice the small performance difference. Depends on the vehicle. The performance difference will be significant with the Maxima, but not so much with the Frontier. It goes hand in hand with the gas mileage difference. > I dragged the same out of Toyota regarding their V6 in the Rav and Camry. > The sad part of it is Toyota admitted the EPA ratings require premium > fuel, yet regular fuel is stated as the requirement. CD |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.