I was wondering if anyone has filled up on anything lower than 91 Octane, we only have 95 or lower and I have been filling up on 95 since I bought the car but I was wondering if the mid range would be OK....does anyone know?
I don't have personal knowledge ... yet. I filled up with mid-grade yesterday and will do a comparison with past experience now that my smart seems to have settled into the 42-43 MPG range. (We have approximately 2,000 miles on the car)
There's an owner on another board who claims to have used nothing but regular in his car without a problem.
I think Smart wants Us to use something around 91-95 range but the only thing that should be affected by lowering the octane is your fuel economy not much else.. Let me ask someone for an updated reason and I'll post his perspective (an ex-Exxon guy)..
91 is the base octane you want to be using in the smart due to its compression and often high RPMs, using normal gas will allow the smart to work but you will not want to push the smart, the burn rate of the fuel is designed for 91+ so anything less then that will cause the smart to not burn/compress/use the gas properly.
The story on octane isn't as straight forward as you might think because there are a couple different ways of defining octane for gasoline.
The 451 manual (and even the gas tank cover) say you should fill the tank with gas with an octane rating of nothing less than 91 RON (Research Octane Number) and preferably 95 RON. If you live in Europe or Australia, gas octane is measured in RON and, hence, you should fill your tank with 91 or 95 octane.
Another way of defining octane is MON, or Motor Octane Number. This is mostly used in aviation and is measured slightly differently... so the MON of a particular gasoline will come out about 8 to 10 points LOWER than RON... same gas, different measurement technique, different number. So, a gas with a RON of 91 will have a MON of 81 or 83.
In North America, octane at the pump is shown in something called PON, or Pump Octane Number, which is mathematically defined as (RON + MON) / 2 (you can actually see this equation on some pumps if you look for it). Since MON is 8-10 points lower than RON, the PON will be 4-5 points lower than RON. Therefore, a 91 RON gas is the same as a 86-87 PON gas (which is why you won't find a gas pump in Europe pumping out anything less than 91 octane and in US/Canada our pumps go down to 87). Therefore, in North America, you're perfectly safe to put 87 octane in your tank (equivalent to 91/92 RON) or 89 octane (equivalent to 93/94 RON).
And to answer that old myth... no, if you put a higher octane gas in your car than the manufacturer's recommended octane you will NOT NOT NOT get better fuel economy or horsepower. Octane is NOT a measure of a gasoline's 'power'... it's purely a measure of its self-combustion under the stress and heat of an engine cylinder. That said, if you put a LOWER octane gas than your manufacturer recommends, you WILL get worse fuel economy and horsepower because your engine will knock (the gas will pre-detonate in the cylinder), your knock sensor will detect this and change your fuel mixture to stop the knocking... this will lower your performance. The Smart engine is rated at ~71 horsepower... you can't increase this by putting a higher octane gas in your engine.
you my friend are starting to stirr the nest of contravercy..
So did Smart know this and compensate for it in their computations? are their requirements to use 91 or higher pre or pos (equivalent to 91/92 RON) or 89 octane (equivalent to 93/94 RON).? Or thid they not take it into consideration, telling us to use 91, a more expensive fuel than 89 in mistake?
I dont think they would make an error that would be so unpopular with the possible clientelle looking at the smarts cost effectiveness in a market that wants to have cars run 100mpg on the cheapest fuel at the pump.
Now check the label on the inside of your fuel filler nozzle. I'll wait.
Did both say "91 RON (minimum)"?
Prove me wrong that PON = (RON + MON) /2. Now prove me wrong that pumps in North America use PON and pumps in Europe (where the car was made) use RON.
I don't care what the dealer said. If they told me to fill it with 95 proof rum but the manual and the car said to fill it with 91 RON I would trust the manual first. To be truthful, my dealer also told me to fill it with 91... but he's a sales guy looking at a number and obviously no understanding of the difference between RON, MON & PON. He's been trained in Europe... but octane isn't octane everywhere around the world.
Ultimately it's up to you... it's your money. I have done my research and have no interest in damaging my wonderful new car. 89 PON is what I'm putting in mine and I have experienced no pinging due to pre-detonation. I'll let you know if I do.
i'll buy that and save a dollar! i've been running 93 octane since new, i'll try BP silver 89 US octane next fill-up. i haven't had my car over 4000 rpms yet (i top out at 75mph when i get the chance) i prefer to keep it at 3000 rpms (60mph). i plan on spending weekends at my dad's cabin a little over 200 miles from home, if i can get away with 45-50mph, i'll do it! it'll take an hour longer, but i should see 50+mpg, i have a good stereo installed, so i'll sit back and enjoy the ride (hoping for cruise control soon)
I was thinking about it last night and realized this:
The guy selling the car at the dealer is just that... a sales guy. He's not a mechanic or a wrench head or an engineer... he's a sales guy. He's good at what he does: sell cars. (S)He probably doesn't know how fuel octane is measured or even what it means.
That said, even if they DID know about octane ratings in Europe and North America... which conversation do you think they'd rather have:
1) "You have to fill it with 91 octane... see... right here it says that... moving on..."; or,
2) "See here where it says fill with 91 octane... fuel is measured differently in Europe and octane is blah blah blah" (gets out pencil to write down equation, etc).
The first one is MUCH easier and quicker. I wouldn't be surprised if they were told not to get into the second conversation because it might make it seem that they're trying to pull a fast one on Mr. New Car Owner.
That said, it's unfortunate because hitting people in the wallet just after they sign on the dotted line to buy the car by saying "you have to fill it with the most expensive gas there is" is not really a selling point.
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