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BrianC

451 Actual Realistic Mileage, Anyone?

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My last fill-up was with mid-grade (89 octane). Mileage on this tank was 43 MPG. We had been averaging 42-43 MPG so no appreciable change. Car has 2300 miles. Driven exclusively in "auto" mode. Usually with driver and passenger. Not much stop & go. About half this tank was freeway miles @ 65-75 MPH. Most of the other half was in a suburban setting with lots of hills.

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My last fill-up was with mid-grade (89 octane). Mileage on this tank was 43 MPG. We had been averaging 42-43 MPG so no appreciable change.

I have been thinking about 89 vs 91 octane for the 451. If the gas mileage is not compromised and if 89 isn't detrimental to the engine, obviously it's the way to go. However, they spec'd 91 octane for a reason and the long-term effects of burning a lesser octane gas is unknown to me. Of course, if predetonation (pinging) is happening then one should up the octane.

Here's what the owner's manual states regarding using lower octane gas. I don't understand the 3rd point regarding the 3000 rpm and light load???

To maintain the engine’s durability and performance, premium unleaded gasoline must be used. If premium unleaded gasoline is not available and low octane fuel is used, follow these precautions:

• Have the fuel tank only partially filled with unleaded regular gasoline and fill up with premium unleaded gasoline as soon as possible.

• Avoid full throttle driving and abrupt acceleration.

• Do not exceed an engine speed of 3000 rpm if the vehicle is loaded with a light load such as two persons and no cargo.

• Do not exceed 2/3 of maximum accelerator pedal position if the vehicle is fully loaded or operating in mountainous terrain.

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Hi,Haven't been on in a while, been driving our SMart around.... We picked it up barely a month ago, and we have 1300+ miles on it already!!! This is what we've noticed in MPG: (we are NY drivers=heavy right foot, btw)1st two tanks about 36-38mpg (about 600 miles)past 4 tank fulls, steady 40-50mpg....We went on a trip out of state, and we logged 55 MPG@65-70, steady, no traffic, 2 people in car w/luggage!!!!woohoo!!I would say we are in the 45mpg range steady now, city and hwy mixed about 40/60.All minimum 92 octane...couple times we tried 94 also

post-5584-1209400429_thumb.jpg

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I have had my 451 for about 3 weeks. I have been keeping track of milage. My driving conditions are:220-250 KM a day.80% highway driving110-125 KM/HrAutomatic.My fills so far have not been full tanks (no premium out where I live so the most I've filled is 24 Litres).7.25 L/100km6.6 L/100km6.25 L/100km6.1 L/100km6.0 L/100km

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I have been thinking about 89 vs 91 octane for the 451. If the gas mileage is not compromised and if 89 isn't detrimental to the engine, obviously it's the way to go. However, they spec'd 91 octane for a reason and the long-term effects of burning a lesser octane gas is unknown to me. Of course, if predetonation (pinging) is happening then one should up the octane.

Here's what the owner's manual states regarding using lower octane gas. I don't understand the 3rd point regarding the 3000 rpm and light load???

To maintain the engine's durability and performance, premium unleaded gasoline must be used. If premium unleaded gasoline is not available and low octane fuel is used, follow these precautions:

• Have the fuel tank only partially filled with unleaded regular gasoline and fill up with premium unleaded gasoline as soon as possible.

• Avoid full throttle driving and abrupt acceleration.

• Do not exceed an engine speed of 3000 rpm if the vehicle is loaded with a light load such as two persons and no cargo.

• Do not exceed 2/3 of maximum accelerator pedal position if the vehicle is fully loaded or operating in mountainous terrain.

There's actually been quite an intersting discussion about this subject on the 451s.com forum. Poster canuck451 has this to say:

'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).

There's plenty of resources on the net if you want to double check what I'm saying. Some starting sources:

http://en.wikipedia.org/wiki/Octane_rating...urement_methods

http://www.torquecars.com/articles/fuel-octane-ratings.php

Google RON MON or gas octane ratings

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."

Interesting point.

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Posted (edited) · Report post

Driven almost 2,000 miles (!) and my mileage is actually IMPROVING. I have no idea how this is possible, but I am thrilled.Started right at 41mpg average, now up to 44, with last two runs at 47mpg.I do use the high grade 93 octane in it, and I do not have a lead foot. Single passenger always, flat mid-western roads, 12 miles to work with exactly one stop sign and a few lights that are almost always green, so it's a pretty straight shot. Speed limits range from 30 to 55 along the route.

Edited by LKern

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Driven almost 2,000 miles (!) and my mileage is actually IMPROVING. I have no idea how this is possible, but I am thrilled.

May or may not be the same with the gassers, but the diesels run a different computer setup that affected the mileage and performance when new. It changed at 1500km and 5000km, with noticeable improvements in FE at those points.NOTE: I don't think the programming setup changes have been confirmed by the manufacturer, but just about all of us have noticed this behaviour.Happy driving.MG

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Mine is approx.8L/100 right now as only 1.5 months old. Mostly stop and go, stop and speed driving and little bit highway so far. I was told that the new engines take a little while to finish "grinding" etc. and mileage will improve as they get broken in. Also depends on driving habits. OK, so I have a heavy foot - get off my case dear! Sorry, talking to my hubby. Ha! :lol:

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Mine is approx.8L/100 right now as only 1.5 months old. Mostly stop and go, stop and speed driving and little bit highway so far. I was told that the new engines take a little while to finish "grinding" etc. and mileage will improve as they get broken in. Also depends on driving habits. OK, so I have a heavy foot - get off my case dear! Sorry, talking to my hubby. Ha! :lol:

What seemed to make a huge difference for me is the oil.. I'm using Mobil 1 Euro-Formula 0W40, the stuff has super high viscosity. We also now have over 18,000 kms on it. Keeps getting better all the time.

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0W40 is super-low, not super-high! At least at 0 degrees C it is.

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What seemed to make a huge difference for me is the oil.. I'm using Mobil 1 Euro-Formula 0W40, the stuff has super high viscosity. We also now have over 18,000 kms on it. Keeps getting better all the time.

Mobil 1 Euro-Formula 0W40 is the standard oil that the smart Centres are using or at least my local smart Centre.

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Mobil 1 Euro-Formula 0W40 is the standard oil that the smart Centres are using or at least my local smart Centre.

You're one of the lucky ones.. It's not standard at our smart Centre, just an expensive option.

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0W40 is super-low, not super-high! At least at 0 degrees C it is.

What I meant was simply that this brand of oil, in North America anyways, has much better viscosity than any other brand with the same ratings.

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Posted (edited) · Report post

If you haven't seen it already, there is a report on International FE results over at thesmartclub

You should check it out and sign in to register your experience.

The April graph tells us that if you're getting 44mpg (Imp) / 37mpg (US) / 6.4l/100km, you are beating the real-world average for the 451.

B :sun:

Edited by bilgladstone

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If you haven't seen it already, there is a report on International FE results over at thesmartclub

You should check it out and sign in to register your experience.

The April graph tells us that if you're getting 44mpg (Imp) / 37mpg (US) / 6.4l/100km, you are beating the real-world average for the 451.

B :sun:

Both the wife & I have lead-feet; not trying to get great mileage. I believe it's just because we've put more miles on than most folks and now have one of the higher mileage 451s (more broken in & loosened up).

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Do you pulse and coast? Do you think that might edge it up to 50mpg?

Nah, I do only a few things... no fast starts, when I come to a stop light or sign I begin coasting as far away as possibe, down a hill I do the same... as long as nobody behind. Also I do a very slow, even accelleration... and if tailgated I go REAL slow... slower... slower.... till they pass me. :)

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Posted (edited) · Report post

3rd tank in a row now that I'm getting over 47 mpg. This one was 5.94L/100 kms or 47.52 MPG (imp). (Odometer now reads 18,640 kms.)

Edited by denisjolicoeur

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I live in Saskatchewan and bought my smart in January, so my first few tanks had abysmal fuel consumption - I am almost ashamed to have my spritmonitor link in my signature :P In the winter, there was a lot of warming up and idling for me. With the help of the summer season and a ScanGauge, things are improving. I don't drive as much as many members (my odom currently reads about 2100km after 4 months) but I think the engine is starting to break in. I got about 81km on ~4.5L on my current tank of gas so things are looking up!

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The trend is improving, that's all that matters.

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wow, reading this I am now very concerned. My new 1 month old 08 Cabrio just finished the third tank and it just passed 1000km, so far I have been unable to hit 400km per tank, I do all city driving tho but it was quite bad isn't it? :unsure:

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wow, reading this I am now very concerned. My new 1 month old 08 Cabrio just finished the third tank and it just passed 1000km, so far I have been unable to hit 400km per tank, I do all city driving tho but it was quite bad isn't it? :unsure:

At only 1,000km, don't worry; the engine isn't even properly run in yet.Bil :sun:

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