Anyone try using Regular unleaded????

[thestevens5]

With the price of gas I just wonder if it makes all that much difference. I've read several articles online saying Diamler Ag recommends premium in all their vehicles

[UNTODDLY]

I did by accident and it KILLED my gas mileage!!!!

[jwight]

Schembri says Regular OK

One of several threads. Premium is recommended for the smart but it will run on 89 octane. Consensus is the few extra $$ for premium are worth it.

[jediknight36]

I dont know about using regular. Most people have been going twice the distance in the smart on one tank of gas than what I can in my car, and pay $20 less, even though it uses premium. If you are in a bind and cant find premium, then go a head, get it, but try to fill it with premium, or the highest to premium you can.

[BigWarpGuy]

I have been using regular in my Smart Fortwo Pure without any problems (none that I have noticed). I am average about 37mpg. With gas prices being lower than it was not that long ago, premium gas is now selling at what regular gas was selling at. It is amazing that we now think it is a bargain when only last year we did not want it to get that high.

[rawlus®]

i'm getting between 41-46mph on premium in mixed driving, 3000K on the odometer. an engine designed to run on premium fuel is going to run more efficiently on premium fuel.
my other two vehicles are not designed for premium and in those i run regular 87 octane. they get about 1/2 the fuel economy the smart does on premium.

[BigWarpGuy]

I will give premium a try and check out the results.

[jwight]

From his blog on smartusainsider.com

There has been some confusion regarding the recommended use of premium fuel which I want to help clarify. As many of you have noted here on the forum, the smart fortwo was engineered to run on premium fuel (91 octane or higher) to provide the best performance and fuel economy. However, in limited and temporary situations, the smart fortwo can run on regular fuel. The owner’s manual says that if premium fuel isn’t available while filling up, drivers can use partial tanks of regular fuel until premium becomes available. You should also try to drive more conservatively if using regular fuel – stressing the car while using regular fuel can negatively affect the car’s durability and performance. Again, to be clear, using premium fuel best protects your car from damage to the engine and catalytic converter. For more information on this topic, you can reference the owner’s manual or contact your local smart center.

[hissingsnake]

High octane gas burns less efficiently. You should get better MPG with 89 octane. I am in my high performance car. However, it may take a hundred miles or so for the computer to adjust. I would reset the computer first by, ie. disconnecting the battery, then hold down the brake pedal to drain the power in the ECU.

The computers of practically any new cars (and most newer cars) would have 2 tunes. One tune would have the best performance in order to achieve the advertised horsepower and torque. The other tune, that cuts timing (thus less power), is just in case the user accidentally put in non-recommended lower octane gas....or even get a bad batch of premium gas somewhere.

Different cars have different threshold of tolerance. If you hear SOME pinging, ease up on the gas (and don't accelerate aggressively) and turn off the A/C. The computer should adjust to lower timing if it keeps sensing the pinging (by its knock sensor). If you get LOTS of pinging or constant pinging with A/C off, hot days, going up steep hilss, etc....then have a bottle (or two) of octane booster ready in the trunk to put into the gas tank (and don't experiment with lower octane again, until at least the cooler months). And get premium in there fast. One bottle of octane booster raises the octane rating up by about 1. Second bottle will give you another 1/2 or less point. Driving with the heater on full blast helps too. Otherwise you could blow the headgasket and warp the heads.

Smart probably tuned the car to run on 91 octane (since some areas don't have 92-93, while those with 92-93 don't have 91). So putting in 92-93 octane might be worse for MPG vs. putting in 89. Or during the next fillup, just try 1/3 of a tank of 87 or 89 octane to see if there's too much pinging for too long. If yes, then fill it up with premium.

[fmaxwell]

It used to be that pinging was nature's way of telling you that you needed more octane. Now most ECUs detect the pinging and retard the timing in response. This stops the pinging, but also reduces power and decreases fuel economy.

As to the AC, it's electrically driven in the Smart, not run off of a belt on the motor like on other cars, so it's not going to have a direct effect on pinging.