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Toyota Avalon Fuel and Fuel System Questions



  • Recentlly I filled my 2002 Avalon XLS with an E10 mixture. Coincidently, my car stalled when I put it in gear. After repeated startings it finally stayed on when I put it in gear. Because I thought the E10 might be responsible, I quickly filled the car with a non-ethanol gasoline after 40 miles. Since then I haven't had any starting problems.

    Has anyone heard of E10 causing any starting problems with the Avalon?
  • jbcameljbcamel Posts: 6
    What grade of gas does the owner's manual say is necessary for the 2008 Avalon XLS?

  • melottmelott Posts: 3
    As spring has come, I have learned that the highway gas mileage of my 2003 Avalon is strongly correlated with temperature, ranging from 22 to 26 highway cruising at 75 mph. I don't know why.
  • finfin atlantaPosts: 591
    All Avalons will run ok on regular, 87 octane, gas. They run better on 89 octane midgrade. For the full power built in to the engine, premium grade, at 91 octane or higher, is necessary. This has been discussed many times in various Avalon boards and there seems to be general agreement on the answer.

    My experience, having owner all three generations of Avalon, is that midgrade gives enough mileage increase to justify the slightly higher price at the pump. And the car runs better than on regular. Moving up to premium produces nothing beyond midgrade in daily driving - not to me anyway.

    Great cars... enjoy one today... :)
  • jbcameljbcamel Posts: 6
    Thanks, but I want to know what the manual says. My husband is a "strictly by the book" guy, Whatever the owner's guide says he'll do.

    So, back to my original question: what does the Owner's Guide say for the 2008 Avalon?

  • finfin atlantaPosts: 591
    Mine is an '07 Limited, not an '08, but the engine settings should be the same. Use 87 octane minimum. If significant knocking occurs, change octane grades or brands of fuel. Engine knocking, if severe, will ruin an engine. Hope this helps.
  • jbcameljbcamel Posts: 6
    Thanks, but again I need to know what the Owner's Manual says.
  • geo123geo123 Posts: 33
    Here you go!

    "Your vehicle must use only unleaded gasoline.
    Unleaded gasoline with an Octane Rating 87 (Research Octane Number
    91) or higher required for optimum engine performance.
    At minimum, the gasoline you use should meet the specifications
    of ASTM D4814 in the U.S.A. and CGSB3.5-M93 in Canada."
  • I posted this elsewhere and thought this could help someone here:
    My 2000 Avalon has +130K and is running well except for intermittent rough starts, had to keep foot slightly on throttle at times. Googled and found it may be IAC valve. I know it's discussed earlier in this forum, but I ended up NOT removing it for cleaning:

    Disconnect neg battery cable first. Next remove the air regulator with the intake hoses attached. The hoses may be somewhat stuck, but are made of a hight quality rubber ($27 toy price for ONE), mine are 8 yrs old and were NOT brittle.

    Then remove the engine cover (easy),disconnecting the pcv valve hose, throttle cables (easy), disconnecting several vacuum hoses (easy) and sensor plugs (easy, if you push the release) but then there are more hoses with slip rings on them that are difficult...the slip rings need small and angled needle nosed pliers to get the right angle to release them. Then, slipping the hose off it's connector requires strong fingers to free them for their connectors. That took the most time, patience and sometimes careful prying.

    Once all that is done-90 minutes for me, there are 4 bolts for the throttle body that are medium easy to loosen with a metric wrench. The throttle body (TB) is now free to flip over, and access to the four screws attaching the iac to the TB is achieved...then comes the next big problem.

    The screws require an exact fitting philips screwdriver to remove...i have read some used an impact driver to remove it...others stripped the screwhead and used either a vise grip or the stripped bolt remover from Sears.

    I gave it a try with my available philips, saw that none of the screws budged, and decided to leave the iac on. Put the TB assembly back on right side up and over the next half hour squirted TB cleaner into the iac opening, letting it drip on to a rag i placed on the bottom of the iac. Also cleaned the TB ports with the cleaner and rag.

    My problem was intermittent rough idle, stalled starts, possibly due to a sticking IAC.

    The sticking is caused by oil vapor deposits on the IAC, i think it comes from the pcv valve, bec i found oil deposits iside the air regulator. Toyota service will recommend replacement at @ $200 for the part, plus labor.

    So after my "cleaning" I replaced everything in reverse order, the hardest part is replacing the slip rings to the orginal positions, tested the startup and there was no rough idling at all.

    It's only been one day, but others have not had their idle problems return after cleaning the IAC.
  • sbarkersbarker Posts: 4
    I have a Toyota Avalon with just 30,000 miles. the car is driven locally every day and has been getting 18.5 - 20.0 city type driving. This morning same type driving it says 16.4 - 16.9 What can couse this? The car runs excellent and is not driven hard at all. Can the dashboard mileage meter be crazy or is this a sign of maintence needed.
  • rpfingstenrpfingsten Posts: 154

    not sure why your mileage decreased, but even so I'd have someone look into that because even you previous mpg estimates seems alittle low to me. My avy avg's between 25 and 27 driving locally ( a mix of city and short hiway driving ). 18 to 20 would really be low in my opinion.

  • Incorrect:
    States that premium fuel is required for the 1999 I have used in in the car since I owned it and have NEVER had a issue now it has 180K and sill runs like new.

    Consumer Guide® Road-Test Evaluation
    Except for more body lean and understeer on twisting roads, an Avalon drives much like the Toyota Camry. Although the Avalon's suspension is firmer, it still absorbs most bumps. Even on wavy roads, the sedan does not bounce or feel mushy. It also corners with good grip and moderate body lean. Because there's a negligible weight difference between Avalon and the V6 Camry, don't expect a discernible difference in acceleration or passing sprints. A test Avalon accelerated to 60 mph in 8.5 seconds--just about exactly as swift as a Camry. Toyota's V6 engine is just as silky smooth in the Avalon as in the Camry, and nearly silent. Better yet, it's complemented by a smooth, responsive automatic transmission. As for gas mileage, an early model averaged 19.4 mpg, driving mostly in rush-hour commutes. The V6 engine requires premium fuel.Space is ample for four adults, and six can tolerate shorter trips in models with the front bench seat. Leg space is generous in the backseat, and rear doors open wide for easy entry/exit. The trunk is wide and deep, with a long, flat floor. Low liftover height makes it easier to load and unload, too. Avalon's dashboard layout and materials are first rate. Large round gauges are legible. Both the stereo and climate controls are high enough to easily see and reach while driving.
  • finfin atlantaPosts: 591
    Actually, looking at what they wrote in the mag... most of it is correct. In general, the weak spots were as listed. Brakes wore out too soon, rotors had to be replaced too often, minor fluid leaks, etc. All discussed here on But it was still a great run of cars, there were not that many problems as the model was improved thru the years. My '99 XL was near perfect. The fuel comment is in fact wrong as you point out, they all run on midgrade just fine. Mine produced better mileage on midgrade (89 octane) so I never used regular (87 in GA). Many of the '95 to '99's are still running here in Atlanta, you see them on the interstate or in a parking lot. Great cars... enjoy yours.. :)
  • Avalons do not require 91 octane fuel. Anyone who says otherwise has never read the owners manual. They may get a few more horsepower from 91 octane gas but anyone without a dynamometer who thinks they can tell the difference in a 3 to 5 horsepower increase is a fool. And how many times do you think you are using anywhere close to the maximum horsepower? Maximum horsepower for the 2018 Avalon is delivered at 6,200 RPM. When was the last time any of the pundits on this web site drove their Avalons at 6,200 RPM? When did you last drive it that hard? My guess is never.

    Here is the 2018 Avalon fuel recommendation from the owner's manual:

    "You must only use unleaded gasoline.
    Select octane rating 87 (Research Octane Number 91) or higher.
    Use of unleaded gasoline with an octane rating lower than 87
    may result in engine knocking. Persistent knocking can lead to
    engine damage.
    At minimum, the gasoline you use should meet the specifications of
    ASTM D4814 in the U.S.A."

    As for the quality of gasoline this is what the manual says:

    "Gasoline quality
    In very few cases, driveability problems may be caused by the brand of gasoline you are using. If driveability problems persist, try changing the brand of
    gasoline. If this does not correct the problem, consult your Toyota dealer."

    It's not a convincing argument to say you have been using XYZ gas for 40 years and NEVER had a problem. I want to hear from the people who have used ABC gas, had problems, switched, and the problem was solved. O! And you can't also have your MAF sensor and fuel injectors cleaned and then claim it was the gas.

    You can find your Toyota manual here:

    You might get better gas mileage using premium gasoline but it has nothing to do with its octane rating. Regular 87 octane gas most often has up to 10% ethanol. Ethanol has lower BTU content than gasoline. You should also get better fuel economy using pure 87 octane gas without ethanol, the same can be said for using premium gas because premium gas in not available with ethanol. I have measured this myself over a 5,000 mile test interval. I got 3% better fuel economy, 24.7 mpg vs 24.0. Not worth the difference in cost of buying pure gas. I don't rely on what the cars computer says. I do it the old fashioned way by logging my mileage and fuel supplied at the pump. I've recorded a mpg range from 18.6 to 31.6 over a 9,000 mile interval under the same driving conditions. A single tank of gas is insufficient for a meaningful test. Even my 5,000 mile test must be considered suspect. After all I was not able to perform it under controlled conditions.

    There is an argument to be made that cars like the Avalon with variable valve timing can slightly improve performance using premium fuel by allowing the valve timing to be optimized. But I have never seen proof. Again anyone who thinks they can feel any difference without a dynamometer is kidding themselves.

    The BTU content of gasoline has nothing to do with the octane rating.
  • kyfdxkyfdx Posts: 70,373
    "because premium gas is not available with ethanol"

    I don't think that's true. Ethanol actually raises the octane rating of gas, even though it has lower BTUs.
    There may be states where premium doesn't contain ethanol (Montana?), but in CARB states, or Midwest states that use reformulated gas, premium definitely contains ethanol.


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