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What about fuel types & gas mileage?

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 Posts: 2,353
    Your salesguy isn't responsible for the warranty maintenance and performance of your car, you are...
  • pscheidpscheid 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 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 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.
  • 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 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 StatesPosts: 6,666
    ...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 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 StatesPosts: 6,666
    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 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.
  • 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?)
  • 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.
  • 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.
  • 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 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 Posts: 325
    are just not built for fuel economy. What type of mileage are you getting?
  • dardson1dardson1 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 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 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 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 Posts: 119
    Yep - they both had/have the 3.73 rear end.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    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 Posts: 413
    Did both have the same brand and type of tires? More agressive tire need more power to turn them.

  • ianshawianshaw Posts: 119
    Yep - both Tahoes had/have the stock Firestones with identical tread patterns.
  • dardson1dardson1 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 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 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 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 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 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).
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