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What about fuel types & gas mileage?

jaydhjaydh Member Posts: 16
My Thousand Oaks Infiniti rep suggested using supreme for the first two to three tank fills and then going to mid grade thereafter. Our driving will be city and freeway with no unnecessary quick starts and no unnecessary quick stops. We have a 6 speed stick G35coupe.


  • zueslewiszueslewis Member Posts: 2,353
    Your salesguy isn't responsible for the warranty maintenance and performance of your car, you are...
  • pscheidpscheid Member Posts: 190
    I have read articles in car mags and consumer reports on this topic that suggest on most cars using a lower than mfg.suggested octane fuel is not a problem. The antiknock sensor eliminates preignition (detonation) to protect the engine, so no knock. A byproduct is a falloff in power and a slight reduction in fuel mileage. Road & Track Tech Tidbits suggested that the $ savings going to a lower than suggested octane is offset by the reduction in get to drive with slightly less power for the same price. Doesn't sound like a bargain to me.
  • zueslewiszueslewis Member Posts: 2,353
    with the 2.4 turbocharged engine. Premium is "recommended". Being an experienced car guy, I figured "what the heck" and used 87 and 89 at first. When I switched back to 91-93, I couldn't believe the difference. There was about a 5-10% power increase and a 2-3 mpg average increase in mileage.

    It makes a difference to me!
  • swschradswschrad Member Posts: 2,171
    and so I would tend to believe that after doing testing nine ways from Sunday on engines and applications (the Four in a focus will perform differently than the same Four in an F350 with duallies in back :-D ), the car companies have a leg to stand on in recommending a particular grade of gas.

    depart at your peril. also known as, You Too can have an Audi that runs like a Yugo... just run it on 87 octane.
  • neptungrllneptungrll Member Posts: 48
    I have had my G35 for over a year, 15,332 miles and I have NEVER put anything but 93 in it. It is worth it to me.
  • tbonertboner Member Posts: 402
    why someone who spends 30 Large on a car is concerned with the extra $0.20/gallon for 91-93 vs the normal 87 octane fuel.

    If you are getting anywhere close to 20MPG, then you are really talking only about $0.01/mile more

    Over 100K miles, you are talking about all of $1000 in added costs.

    Heck, why complain about fuel prices at all.

    Same 100K period, same 20MPG and $2/gallon fuel, you will pay $10K in total fuel costs.

    You still paid more than that for the vehicle...

  • corvettecorvette United StatesMember Posts: 8,547
    ...why, with all the technological advances in cars today, why premium is still called for in applications that do not have a turbo or supercharger. Generally, it is "premium" cars like Infiniti or Lexus which call for it, but it seems as if they could design their cars to run on regular grade, even if it meant a slight decrease in horsepower. The GM Northstar engines no longer require premium, and they made this change with no perceptible decrease in horsepower. I find it ironic that although Lexus cars are designed to minimize vehicle-induced irritation, they require premium fuel. How irritating!
  • swschradswschrad Member Posts: 2,171
    fact is the automaker decided that they wanted higher octane fuel, designed for it, and you bought the car. you didn't ask enough questions if you're not happy with the results.
  • corvettecorvette United StatesMember Posts: 8,547
    I was just lamenting that it seems inappropriate for a family car like the Camry V6, Sienna, Maxima, or Altima 3.5 to demand premium fuel. I suppose that in higher echelons such as Lexus, buyers expect these ongoing expenses.
  • swschradswschrad Member Posts: 2,171
    it took several months chasing facts before I decided that what I really wanted was, in fact, what I should have... an exploder with the trailering package and V8. along the way I looked under a few hoods, and slid under a few vehicles to see what the underside looked like.

    I have a must-have list that is a little different than some, though. MUST have blower motor replaceable from the engine compartment. MUST run on regular. MUST be able to play greenie-CDs in both dash and cartridge changers. MUST be distributorless. MUST have easy access to regular maintenance items, including those in the 60,000 and 90,000 recommendations. MUST have side or curtain airbags. MUST have high domestic content, including specifically engine, tranny, and axle assemblies. MUST have decent access to punch a firewall hole, grommet it, and run extra wiring through it and inside the frame front or back.

    I got a few surprises, too... like the magic disappearing display on the radio faceplate, but I knew I could get it out and get into it, so I was able to fix it. but I also picked a good truck, and having had the training to let little crud slide that doesn't matter (which started with a couple medical issues of note,) haven't lost any hair over "features" and "improvements" in my ride.

    which is good, because there's damn little hair left to lose.
  • 5speeder5speeder Member Posts: 97
    neptungrll--What octane does your G35 owner's manual call for? If less than 93, I'm curious as to why you always use 93.

    Just wondering if there's ever a good reason to us a HIGHER octane than the manufacturer recommends. (My Passat calls for 91, so I never use 92 or 93 when 91 is available. Am I missing something?)
  • eticketrideeticketride Member Posts: 53
    I have tested both 87 and 91 fuel grades in my 2003 G35 Sedan. The manual states that you can use 87 (sedan), but for optimal performance use 91 or better. 91 is the highest available in San Diego that I have found. My personal experience is that I lost a little power by switching from 91 to 87. My gas mileage stayed the same at 19 mpg. Since most of my driving is commuting in traffic, I don't get a chance to really push my car. So I mainly put in 87. At $2.50/gallon, it is hard me to justify using 91 for commuting in traffic...Each person will have their own preferences. Basically, do your own experiment and then make a decision.
  • redz06redz06 Member Posts: 25
    I have almost 12k miles on my G35 sedan and all but two tankfuls have been 87 octane. I ran two tanks of 93 octane and found that it just did not make a perceptible difference in real world driving. Sure, if I was going to the track or going to put the car on a chassis dyno, I would put the 93 octane in, but I am sure that the difference between 87 octane and 93 octane could not be more than 5 rwhp. It has not hurt the performance, it has not hurt the mileage, and it has not hurt the reliability, as the ECU will pull back the timing slightly if any knocking is detected.
  • asmith10asmith10 Member Posts: 2
    I am trying to help my tahoe get better gas mileage. If anyone knows of anything I could do to my truck to get better mileage I would appreciate if they could tell me what to do, and also if you could offer where I could have it done. Thanks.
  • swschradswschrad Member Posts: 2,171
    1) keep your tires inflated to the proper pressure (see doorjamb.) this prevents squirm and energy loss developed in continually forcing all parts of the tire to go in the same direction.

    2) get the extra weight out of the vehicle... all the spare parts, tools, mother-in-law, your usual cliche items.

    3) put in a new air filter at least every 30,000 miles.

    4) use lightest SAE oil grade recommended and change oil and filter on the earliest recommended schedule in your manual for the way you drive.

    all these will make small but noticeable improvements. the biggest thing you can do it

    5) tape a raw egg to the gas pedal, and tape a raw egg to the brake pedal. drive so you don't crush the eggs.

    all told, this is good for at least 20% improvement in gas mileage for most drivers, and possibly more.


    there is no magic elixir, additive, bolt-on, replacement, or imagined potion or component that will make a damn bit of difference to a car -- any car -- in tune and in good mechanical condition. not one damn bit. so don't waste your money chasing any of them.
  • malachy72malachy72 Member Posts: 325
    are just not built for fuel economy. What type of mileage are you getting?
  • dardson1dardson1 Member Posts: 696
    You didn't say what year, 2 or 4wd, which engine, and what milage you're getting. I'm kinda nutty about keeping track of milage (dividing fuel purchased by miles driven) after each fill-up. I have a 2wd '02 with the 5.3 and consistently get high 14's and even 15+ once in a while.....all in stop and go driving.
         I have posted many times on various message boards that I had an 01 Toyota minivan bought because the window sticker boasted 19mpg city. Over the 18 months I owned the Sienna I averaged mid 16's mpg using premium fuel (per the book.) Pound for pound my Tahoe is actually more fuel efficient. Dollar for dollar and based on my monthly credit card statement, it's been a wash since I traded in the minivan.
          Swschrad is correct. While I don't go overboard, I do drive conservatively. You can drop milage 10-15% with a lead foot (I tried it through one tank and got high 12's mpg.) At a quick change oil place some kid put 28psi in all the tires instead of the recommended 35psi. Milage dropped 10% for several tanks until I figured out what happened. Immediately went back up after I put the correct psi back in the tires.
        Drive conservatively and keep the tire pressure at recommended psi. Having had an Expedition (that I really liked but mostly got 12/13 mpg) I feel like I'm driving an econo-car. I filled up Saturday, the weather was cool the last two weeks so I wasn't using the AC, and I assume I'm still buying the summer-blend fuel that yeilds better milage, I got 15.79 mpg all city driving. Amazing for a car this big, heavy, and powerful. Love my Tahoe!
  • fkozilfkozil Member Posts: 65
    Even though I have a Suburban now, I do a lot of highway driving and have found that the cruise control helps keep the mileage in check.

    Also, I believe a light weight synthetic oil, either 5w 30 or 0w 30 will help increase fuel mileage too.
  • ianshawianshaw Member Posts: 119
    My $.02

    I have had two basically identical 2002 4x4 Tahoes with the 5.3 engine. The first one consistently got 18-19.5 mpg in highway driving. (I do very little stop and go driving in my Tahoe). My new one consistently gets 16.5-17.5 mpg on the highway. I drive them the same (conservatively), always fill the tires to full pressure and religiously change oil and filter every 3k with 5w-30.

    My experience tells me that some vehicles will just get better gas mileage than others.

    (On the other hand - my new Tahoe does have some problems with alignment. Although the dealership has checked twice and said the alignment is good, my front wheel tread began to scallop in only 5k miles. Perhaps this alignment problem could be causing enough drag to reduce my gas mileage? Could this be true? )
  • fkozilfkozil Member Posts: 65
    Did both '02 Tahoes have the same rear gear ratio?

    My '03 Tahoe had a 3.42 rear and my Suburban has a 3.73 rear.

    Even though it doesn't seem like much in terms of numbers, the rear ratio will make a noticeable difference.
  • ianshawianshaw Member Posts: 119
    Yep - they both had/have the 3.73 rear end.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaMember Posts: 64,482
    Alignment can make a difference.

    Also synthetic oil might help a little because you'll get a faster warmup generally.

    But you are driving a big heavy brick so there are limits here....
  • oldharryoldharry Member Posts: 413
    Did both have the same brand and type of tires? More agressive tire need more power to turn them.

  • ianshawianshaw Member Posts: 119
    Yep - both Tahoes had/have the stock Firestones with identical tread patterns.
  • dardson1dardson1 Member Posts: 696
    why GM bothers to make the 4.8. In theory the smaller engine with considerably less torque and slightly less HP ought to (1) get better milage or (2) post better milage on the sticker to help GM's overall fuel averages. I see way more 4.8's on the lots lately but the sticker posts the same milage numbers as the 5.3. Can't see why you'd opt for the smaller less powerful engine with no advantage other than the tiny difference in price.
  • q45manq45man Member Posts: 416
    Creating efficient power at 55 mph to pull slight inclines without downshifting is a very fine line.
    A 10% smaller displacement may have to turn up to 10% more rpm to generate enough thus washing most/much of the gain of a smaller engine........if it gets 0.49 mpg better [2-6% better] you might not see it due to rounding of the numbers on the EPA sticker.
  • fortopfortop Member Posts: 239
    I have consistently achieved in every vehicle I have owned in the past few years. As mentioned above, here are the methods used to get this result, in order of importance:
    1) Drive convervatively - easy away from traffic light stops, accelerate slowly, don't floor the accelerator to pass, always drive the speed limit.
    2) Use cruise control even in city driving. Set the cruise and keeep your foot off the brake whenever possible - anticipate upcoming red lights and turn cruise off - coast to the stop light.
    3)Don't idle - start up and go, don't sit and fiddle with the radio controls or your seat belt, try to avoid rush hour traffic, do your shopping at the least busy times of the day or night.
    This type of driving will almost make you go insane since everyone is blasting past you (nobody drives the speed limit), but it gives you something to do when driving to/from work, makes you a more alert driver, and puts a few extra dollars in your pocket rather than in your gas tank.
    Recent results:
    2002 Yukon 5.3/3.73 loaded - 17-18 mpg city
    2002 Tahoe 4.8/3.42 basic LS - 18-20 mpg city
    2003 Tahoe 4.8/3.42 basic LS - 18-20 mpg city
    2003 Sierra 5.3/3.42 SLE - 17-18.5 mpg city
    I never take extended drives on the highway.
  • dardson1dardson1 Member Posts: 696
    I haven't seen you posting lately. I don't think there are many Tahoe drivers who give a hoot about mpg. I was taught by my dear departed dad that the measure of the car was how fast it would go on the straight away and what kind of milage it got, lol. He's been dead a decade and I've been driving 40 years, but to this day I still check miles driven divided by fuel purchased after every tank.
         I've tried some of your techniques although I admit I refuse to drive in summer weather without the a/c. I'm guilty of hitting the gas to merge into traffic, but I always cut off my engine waiting at the drive-ups and use the cruise when it's appropriate. I get IMHO very decent milage in my big 2wd 5.3 driving reasonably conservatively....but 15 +/- city is all I can do. Wonder if my 3500 altitude has some affect.
        Looks like the 4.8 by your numbers does 10% better. I suppose it's a silly question considering your driving habits, but do you ever miss the extra hp? I'm trading soon and looks like the 4.8 would suit me fine as I never tow. While I drive like a grandpa around town, I hook up the Valentine and drive 90ish on the road. Even at that speed I get mid 17's highway and mid 18's if I slow it down to my Tahoe.
  • ianshawianshaw Member Posts: 119
    18mpg sounds pretty good at 80 mph. I can't get my 5.3l 4x4 Tahoe to get 18 mph even when I am slowed down to 70-75 mph and driving conservatively up hills.

    With regard to 90 mph. Do you drive that fast on the original tires? I ask because my Tahoe doesn't feel very stable at 80 mph, let alone 90 mph. The thing wants to wander all over the road and requires constant wheel adjustments. I understand that the wandering gets much better when you replace the stock tires - but I was just wondering if you brave the original tires at 90+ mph?
  • ianshawianshaw Member Posts: 119
    Several posts back there was a comment about elevation. Does elevation have an impact on mileage? I live at 6500 feet and typically drive between 6000-8800 feet everywhere I go. Could that be giving me low mileage? (However, I drove my previous 02 Tahoe at the same elevations and got significantly better mileage than my current Tahoe).
  • zueslewiszueslewis Member Posts: 2,353
    I had a '92 Yukon and lived in central Wyoming, regularly driving out of the mountains (I lived at 7,000 ft) to much lower areas (like home to Texas, elevation 20 ft (near Houston). My fuel mileage went up 5-6 mpg!

    With the elevation, you have a much lower oxygen level - it takes more fuel to provide a proper fuel/air mixture. Just like how the lack of oxygen makes it where your biscuits don't brown and water takes longer to boil and you need to make recipe additions.
  • dardson1dardson1 Member Posts: 696
    Yes, I do drive on the stock FS Wilderness LE's. After much research and a willingness to cough up the money for new tires I came to no conclusion. I decided the FS controversy was a tempest in a teapot. Never feel a "wandering" problem, but I only drive (too) fast on long, flat, West Texas interstate highways which is not exactly demanding driving conditions.
       I'm very surprised at my good milage. I had often read GM did better than everyone else on mpg. It does WAY better than my old Expedition and about the same as my Jeep GC (six) and Ford Explorer (six). No complaints.
  • swschradswschrad Member Posts: 2,171
    there was very little mumble about the wilderness LEs, during the time the AT line as supplied to ford was proven to be extremely variable in build details and iffy in service (or worse.) there was more mumble about the Steeltex, some small number of which were recalled, most of which weren't.

    up here in cold weather country, I still see a lot of both mounted on GMs.

    I never liked the wilderness ATs I had, just no side grip at all and not useful in snow, and the generals I got adjusted into courtesy of ford have done very much better. essentially no difference in fuel economy at all between the two that I can tell. neither is designed for economy first, they are both all-weather types.
  • q45manq45man Member Posts: 416
    "With the elevation, you have a much lower oxygen level - it takes more fuel to provide a proper fuel/air mixture. "

    Say what? the Obd2 system adjusts cruise at 14.7 AF regardless of altitude.[up to the 20% limit]
    Air density [O2 content]decreases 1% per 333 feet AMSL so the ecu reduces fuel injector open time by 1%.

    The problem is you have to open the throttle more to generate the same power at altitude. At 8,000 feet the engine will produce 24% less maximum horsepower or torque [assuming the same air temperature [usually cooler]. Each 11F decreases/increases density by 1%.
  • zueslewiszueslewis Member Posts: 2,353
    I understand what you're saying, but I was trying to keep it simple - no offense to the person asking the question.
  • ianshawianshaw Member Posts: 119
    Zueslewis - no offense taken - simple is good for me!! Afterall, I too am a hick from Wyoming!!!

    I find it amazing that my Tahoe has 24% less power at 8000 feet. That's a noticeable difference. I am almost always towing my trailer between 7500-10,000 feet and have always laughed at those people on RV chat forums who say "you don't even feel a 2500 pound trailer behind a 1500 series Chevy." I sure do!! I have to put my foot a long way into the throttle to make the thing move!

    This helps explain my bad gas mileage - thanks!
  • zueslewiszueslewis Member Posts: 2,353
    I had a '92 Suzuki GSXR-1100 - the front end wouldn't pull up at that altitude!
  • jeff331jeff331 Member Posts: 21
    ianshaw, you might consider getting a new intake kit and cat-back exhaust system for your truck. The extra airflow through the engine will help get back a little of that lost power. By a seat of the pants measurement, it has helped here in the mountains of Colorado (better reaction from the engine when trying to pass a Geo Metro going up skiing). Or just spring for a supercharger!
  • fortopfortop Member Posts: 239
    an additional 2 mpg. I never missed the difference in horsepower or torque, considering my driving style - a 6 cylinder would probably be adequate. However, 4.8s are not as popular on resale, so I won't be buying them on the next vehicle until the resale market changes (remember I buy a new vehicle every 6 months - that Sierra has 2K and I'll be selling or trading in the next two weeks.)
    My Tucson elevation is 2410' - don't know if your +1000 feet makes a difference - but I doubt it means much (but I am not a fuel consumption scientist).
    I may go back to a 5.3/3.42 2WD Tahoe or Yukon on the next buy since the resale is still holding up better than the pickups. Too bad you get less standard options for your money every year and the price still goes up. The best overall buy on a used Tahoe/Yukon is now the 2002 model - before the big "de-contenting" started.
    I would not drive in hot weather without A/C on either, but most people now drive with the A/C on when it is a pleasant 60-70 degrees outside - I don't do that.
  • dardson1dardson1 Member Posts: 696
    we are on the same page. After much research I've concluded my '02 was a bargain. I have to add about $2500 in options to a new one to get one with the same stuff as my '02. Even with my max GMCard money I can't do any better out the door. Since I posted my last message I got my very best city milage ever....17.13. I can hardly believe it although I got high 16's last October (I keep pretty good records). I suspect it's a combination of no AC, conservative driving, and the last of the summer fuel. My wife drives a Lexus ES300. Month to month and driving similar miles, her credit card fuel bill is about the same as mine. Interesting, considering I'm driving a very un-PC gas hog. Thanks for the reply. Love my Tahoe.
  • msisengmsiseng Member Posts: 369
    Many service stations are dishonest and put 87 octane in premium pumps. If you really think you get premium all the time, think again.

    Most stations are regulated once or twice a year and they know when the inspectors are due to visit (usually the state Dept. of Agriculture). This is true from state to state. How do I know this? Well, because my "acquaintances" own a conglomerate of different branded stations in Virginia, Maryland and Washington, DC. Guess what? They get gas from the same 14 wheeler trucks!

    In Virginia, they put oxygen into the gas during the winter months and fuel economy really suffers. They do this to reduce emissions as well as for other undisclosed reasons.

    Sad and we are all hosed as consumers. If you purchase premium it is probable that it is the same gas as in the lesser octane pumps.

    Many news reporters ran lead stories in the 1980's and found the above to be true. I am sad to report things have not changed in 20 years!
  • swschradswschrad Member Posts: 2,171
    the residual scuz from 6000 gallons of dog pee in 6000 gallons of gas is just about undetectable, and it won't make any difference. you don't reserve one tanker for 93 octane and ten for 87, that's idiotic logistics.

    we have a small chain of 6 or 8 stations in the greater metro twin cities area that is served from one tanker truck, back and forth to the terminal, all the time. not a problem. multiple trucking companies use the same tankers to haul to citgo, ashland, mobil, BP Amoco, no-name, conoco, you have it, and it doesn't matter.

    if you want to know when the inspection service will be coming by to check the pump accuracy and take a sample, look at the bloody inspection sticker on the pump. right over there, by the nozzle. the year and month are punched out. guess what, they inspect just in time to keep the station running if they're legit, because there aren't enough inspectors to do it earlier.

    some operators may try to screw you. this will generally result in hot little numbers running like lawnmowers, and that guy will get a rep for "watered gas" or punk fuel. he won't be around long.
  • fjm1fjm1 Member Posts: 137
    So what's your point? Is there such a thing as premium gas or are we all just dupes?
  • swschradswschrad Member Posts: 2,171
    meaning octanes 92-93 in rating. I will go so far as declare that it really IS premium in most station's tanks. it would certainly have Mike Wallace with a camera crew on the doorsteps if refinery and pipeline folks were selling anything else as premium.

    where you have 87 or 89 marked (and marked up as) premium, you have an individual thief who probably is also fiddling the books and not sending in FICA tax witholding on the cashiers' salaries. you should be able to tell it by hitting the pedal on your speedster and having it respond like a lawn tractor.

    if you think Bilge Billy's is selling low-test as premium, just whistle up the tip line at Eyewitless Action Hometeam Power News TV33, give 'em an interview, they'll fill a gallon can and have it analyzed, and see what results. if you can sell it to them, they'll find out.
  • redz06redz06 Member Posts: 25
    There is such a thing as premium gasoline and it is made in the refineries. Unfortunately what arrives at your pump may or may not be the same thing. Have you ever heard of premium gasoline trucks? How about premium gasoline pipelines? No? Well all of the gas is being shipped in the same way. IMHO, if more testing was being done at the pumps, people would be shocked at the result.
  • swschradswschrad Member Posts: 2,171
    when you pump out 6000 gallons of anything, there is probably less than a gallon of residual in the tanker truck. when they refill at the refinery with 93 octane and take it out to a gas station, that is 1 gallon in 6000 of lower grade product. guess what, it's not going to change the octane rating of that 93 in any measurable way... even if the last load was diesel #1 and this one is 93 octane gas.

    if it was dog pee, it wouldn't make a testable difference in the new load of fuel.

    do the math...
  • nmotennmoten Member Posts: 4
    I had same scalloping problem with Firestone Wildernesss tires on 2002 Tahoe. I had front end aligned and rotated tires 7500-10,000 miles.

    At 46,000 miles I replaced 3 tires, added the spare. Independent tire man said maybe front shocks are not heavy enough, and allow bouncing...or it's the tires? His opinion was that alignment is not the problem. who knows.?

    Friend who replaced shocks said that did not cure the scalloping. New tires improved ride 100 %, but will likely wear the same as previous ones.
  • corvettecorvette United StatesMember Posts: 8,547
    I was under the impression that tanker trucks had separate compartments for regular, mid-grade, and premium fuel, so that one truck could make one trip to each station to refill the tanks.
  • swschradswschrad Member Posts: 2,171
    but that doesn't mean they keep tank 1, for instance, reserved. some of the newer ones I am next to at a light have rotating indicator wheels near each product valve, which can be set to indicate what is loaded... like light fuel oil, unl gas, etc.

    I also see one and two section tankers periodically, passing me while some pinhead in front is trying to figure out whether he should let out the clutch on a green light, a red light, or a purple-striped light :(
  • swschradswschrad Member Posts: 2,171
    the hot dogs, coffees, and snacks do kinda creep onto the gas card bill if you're not careful about it. so that's not my favorite measurement, it's several layers removed from the actual gas used versus miles driven.
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