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RCF50 发表于 2018-10-23 22:42 
google后再发言，别误导别人
再加点给你：
I answered this question only to help people understand the makeup of gasoline: what are you putting in your RX when you press the "91" button & why. With newer cars, this question is really moot. Your computer management system reads the octane and quality of fuel entering the manifold and then makes adjustments in the engine accordingly. Slightly older cars that tell you to use 91, go on to say that using 87 will result in lower performance (computer detuning); not warranty invalidation (except for exotics, like Ferrari). I've always recognized that car manufacturers set octane ratings for engines under stress, so the engine will always be protected against pre-detonation. But it used to be that when an engine wasn't under such stress, say when you're driving to work or shopping, use of a lower octane was fine to save money, and you didn't experience any reduction in performance because computers weren't set to automatically adjust the engine for 87. OBD-1 was the beginning of computers taking gasoline tweaking out of our hands, and today's engines run less risk of damage from inexperienced people. So, the point is that ANY car as new as ANY Lexus RX can use either octane rating, you'll just suffer a slight drop in performance with 87, but I don't think anyone would notice the difference; except an old fanatic like me.
There is no "BEST: octane. It's really just an equation: Octane/$. The newest cars have a computer management system that reads what's going into the manifold and adjusts the engine (spark timing) accordingly. Here, any octane rating can be adapted safely. Slightly older cars do much the same, but limit themselves to 91 & 87. Older cars, without "modern" computers, don't adjust for octane. They run maximum power, unadjusted on any mix of octane/septane (all octane ratings contain the same number of carbon atoms per volume and produce the same energy, except where other fuels are included, like alcohol). With these engines you can tweak your fuels. You just have to be careful about excessive heat that causes pre-detonation when running the engine under conditions that no one will ever see on the street. When "pushing" these engines and you hear a "knock," ease off. This is how Ferrari and other exotics that are designed for pure octane (96% octane + 4% additives) send cars to America where this fuel isn't available at local gas stations anymore. They automatically adjust for 91, 87, or even lower fuel ratings by backing off the spark timing, then limit the throttle. THE MORAL OF THIS STORY is, don't overthink octane ratings for street cars. ALL modern cars can handle any pump gas you can find, or older cars will produce a "ping" that tells you to ease up. But this only happens under the most intense, severe conditions, like racing. |
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大头怀念的北京小吃（十）-- 稻香村的桂花糕 (2011-5-2) datou2z .gif)
发表于 2018-10-23 12:07
LZ问的是澳大利亚的情况
