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I read many articles online and people have different opinions about this issue. Some say 89 is the best for acceleration. Others say 87 is just fine.

I'm worried only about the health of my car. So I read my user manual. Here are the screenshots. I'm not sure, but SE probably stands for sport edition. So should I use better than 87? I just want to use whatever is best for my RAV4's health.

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  • What country do you live in? Barely can find 91 anymore in Australia and I certainly wouldn't put in anything less than 10 years old. – Steve Oakes May 25 '16 at 14:12
  • U.S. California – Emily May 25 '16 at 14:45
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Realistically, if the manual and the manufacturer are stating you should use 87 octane, that's really what you should use. If you purchase more expensive 89, 91, or 93, you are just wasting money. The higher the octane rating, the harder it is for fuel to burn (or ignite). If the vehicle was specified to use 93, then that's what you should buy or you risk engine damage. You run no risk to the engine by running what the manufacturer says. You'll also gain no performance advantage from running the higher octane, mainly because the engine (and computer tune) are not designed to use it.

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    Thank you very much. I'm confused because the manual (in the images above) says 87 (Research Octane Number 91) or higher. And that is bothering me. If it was only 87, then it would say 87 period. Why would they mention 91 at all ? – – Emily May 22 '16 at 22:58
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    Okay so I guess 87 is for the U.S. customers like myself, and 91 is for outside of U.S, maybe Japan. I've never seen 91 anyway . All gas station I've ever visited have 87,89 and 93. So, I'll go with 87, as you recommend. Thank You! – Emily May 22 '16 at 23:10
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    many countries outside of the US use RON only at the pump. Much of europe, australia and new zealand from personal experience all use RON. So yes, the manual states both to avoid having to print two manuals – Leliel May 23 '16 at 0:59
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    @Emily, gas stations in higher elevations offer a different range of octanes; in Colorado it's typically 85, 87, & 91. – Ghillie Dhu May 23 '16 at 2:20
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    They say 87 or higher because putting higher rated gasoline in the car will only harm your pocketbook, not your car. If they simply said "87" and someone who didn't understand what's really going on pulls into a station that only had 89 available they need to understand that it's ok to pump that. – Loren Pechtel May 23 '16 at 5:01
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The acid test is if you try a lower octane fuel, if you hear any "knocking" sounds under hard acceleration (perhaps up a hill), then you definitely need a higher octane rating. As Paulster2 mentions, there will not be any performance improvement, in spite of what a lot of people say. The octane rating is just a measure of resistance to knocking. I have a 2003 Toyota Celica GT-S that recommends premium and it runs fine on mid-grade, saving me $2.00 or more on every tank of gas.

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    this isn't entirely true for more recent vehicles. You won't notice knocking until you're completely outside the range the ECU can compensate for by detuning the engine. What you'll probably notice first is loss of power and fuel efficiency if you're feeding it too low an octane. – Leliel May 23 '16 at 1:01
  • How is it possible that a 2003 Toyota requires a higher grade gas than the 2016 RAV4 ? – Emily May 23 '16 at 1:04
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    Most likely, because during those 13 years the fuel supply industry moved towards supplying lower octane gasoline, with a higher proportion of biofuel additives like ethanol. (I'm not in the US so I don't know the exact details of the situation there). The first major shift to lower octane fuels was when lead additives became illegal, but the trend has continued downwards since then. You can design an engine to run on pretty much any octane rating - the important factor is what is most commonly available at the pumps, in the country where it is going to be driven. – alephzero May 23 '16 at 3:29
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    ... For example in the UK, the "standard grade" is 95 RON, with 97 widely available for "high performance" cars, and much more limited availability of 99, which is only sold by one national chain of gas stations, and by one of the "big four" UK supermarket chains. – alephzero May 23 '16 at 3:37
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    @Emily Because a GT-S is a sports car with a sport-tuned engine, while the Rav4 is not. – Joe May 23 '16 at 15:14
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87 will work, 89 is optimal, 93 will also work but uses a bit more (will start to run leaner but the computer easily compensates but using more fuel) 87 better for winter (no difference over 89), 89 better for summer (helps when underhood is HOT when you have the A/C running AND trying to keep the engine around operating temp.

I would maybe avoid the absolute cheapest/oldest gas stations as there might be water/rust contamination issues. That would pose a greater threat to your engines health than just running 87 all the time.

  • Thank you +1. You say 89 is optimal? Do you mean 89 is ideal for the "car's health" ? – Emily May 23 '16 at 2:25
  • @Emily a higher octane fuel will reduce the possibility of preignition, which will occur with 87 octane under certain conditions, and possibly even with 89. The engine computer will adjust if preignition is detected by adjusting timing and reducing engine output. Conditions are heat and load dependent, more of either requires a higher octane rating to prevent preignition at the same degree of ignition timing. – Richie Frame May 23 '16 at 5:47
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    Could you elaborate how you decided that 89 is somehow optimal? Manufacturer recommends 87 and up, what makes you think 87 is not optimal? And why would 93 be lean? And @RichieFrame, how are you so sure that 87 will preignite on this specific car? – I have no idea what I'm doing May 23 '16 at 7:44
  • @RichieFrame If the engine was designed for 87, there already is no possibility for preignition with fuel rated 87. – Agent_L May 23 '16 at 17:11
  • @Agent_L what makes you think it was designed specifically for 87? Because the manual says "87 or higher" ? Modern engines are complex machines designed to minimize preignition under a wide range of typical conditions, but it is certainly possible to operate outside of those conditions, in which case the engine will detect preignition, and adjust timing to compensate. Imagine a hot engine, 115F air temp, going up a hill, while pulling a full trailer – Richie Frame May 23 '16 at 18:42
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If the manual says 87 octane (or higher), that is all you need to run, 87 octane gas. The engine is designed to run at that octane rating optimally. You can run higher octane gasoline, but all you are doing is spending money you don't need to spend. My daughters Acura TL requires 93 octane fuel and running less impacts performance and can ping. My Ecoboost twin turbo is designed for 87 octane fuel and runs perfect all day long as it was designed to run on 87 Octane. Towing a camper makes no difference as the computer compensates. Higher octane for towing would help but isn't necessary ass the computer compensates for the octane fuel used. You can go higher, but shouldn't go lower than the minimum required.

Sunoco used to have a pump with five grades of fuel years ago all the way down to 85 octane (could blend 85, 87, 89, 91 and 93 at the pump). Sunoco 85 Octane would be used only for low compression engines or at the time, people trying to save some money as it was the least expensive fuel then.

Use a good grade 87 octane fuel and save your money.

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I recommend using 89 . I have 2015 RAV4 . 89 does give you a better acceleration, you are right.

So go with 89 . This is the golden average . Your manual says 87 or higher . So anything above 87 is okay. However, i wouldn't go with 93 . Be cautious 93 may result in unburnt fuel that is not very good

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Every modern (fuel injected) car will run fine on any type of gasoline you can get on a decent gas station. The car has an engine computer that adjusts many parameters multiple times per second to get optimal performance no matter the temperature, air pressure, octane rating, throttle position, hill slope etc.

A different octane rating may make a very small difference in mileage or peak performance. I personally tank the cheapest. Never experienced any measurable difference.

The manufacturer probably has to put octane rating in the manual to get certification right (otherwise someone would tank 50% water and sue, claiming that is runs sluggish...).

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    That's just wrong. – I have no idea what I'm doing May 23 '16 at 9:28
  • Terrible answer. Yes, a car ECU considers many parameters but to suggest that it considers all ranges of parameters is just wrong. – Steve Oakes May 25 '16 at 14:10

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