Fuel question

[PE#454]

In another (Abarth NOW) thread were the following comments:

Cogtooth wrote,  I'm kind of thinking that being able to use regular gas with better economy might be a better choice if I don't sacrifice too much cornering fun with a sport.

CaliberSRT4 wrote, Even the regular 500s are recommended to run Premium fuel, but can also use 87 octane….

I bought my MINI S during the gas shortage in the summer of 2005. For my second (or perhaps third) trip to the gas station I had to pump regular because there was no premium available. I believe I only put in enough gas to last a few days until I could fill up with premium. I noticed such a significant difference in performance (i.e., knocking) that it scared me off of ever using regular again, so, 39,000 miles later, my gas tank has since consumed only the finest octane available.

My question is--what are the potential consequences of using regular gas versus premium in the Fiat 500? And would you use regular consistently or intermittently/alternate with premium?

[5*(10)^2]

Your MINI S is a FI engine. FI engines tend to be more sensitive to octane rating. I actually helped to tune NA and FI engines in the past.

I would still consider the multiair that we will be receiving to be NA, so I reckon 87 would still be quite ok.

Do you still have your MINI S? Fill her up with 100 octane unleaded of course. It might even fly!

[MrJones]

PE#454 wrote

My question is--what are the potential consequences of using regular gas versus premium in the Fiat 500?

Consequences= about $0.26/gallon

I don't know jack about fuel types, but these guys probably do. Maybe you'll find some useful information there?

[Gavin]

my question....

here our octanes are 87,89,91 (sometime 86?, 89,91)

is there any benefit going 89, or should you just go 87 or 91?

Nobody ever mentions the medium grade...always either 87 for savings vs 91 for performance...

Gavin

[spindoc]

Thanks for the Car Talk link.  It'll be interesting to see what differences we may or may not get in performance or mileage with different octane ratings.

[CaliberSRT4]

You should have no issues running 87 octane. When running lower octane gasoline, the ECU will retard engine timing when knock is detected. So, 87 is perfectly safe to run, but the best performance will be achieved with premium as engine timing will not be retarded. This is why the owner's manual will probably tell you "87 octane acceptable, premium recommended".

Mid-grade 89 octane will be between the two, perhaps some knock and therefore retardation of timing, but not as much as regular grade.

Basically, you will get a bit more power running premium.

[Giallo Edizione]

I'm not expert ( on this or much else for that matter) but the lore I read is that higher octane will give better mileage per gallon ( think about it-if you get more power per gallon then fewer gallons needed to do the same work), but not enough to make up for the difference in cost over lower octane fuels. There is a fun-factor in the pricing spread.

[Alvon Elrod]

My opinion is the same as the previous post.  Furthermore, you may get slightly better gas mpg when running premium, but probably not enough to justify the cost difference.  That's something that you could easily test by running a few tanks of premium and running a few tanks of regular, and compare the overall mpg for the intervals that you drive with the different fuels.  

Just to throw some numbers out there, let's say that you are a very conservative driver and get 38 mpg with regular (at $3.70/gallon) and 40 mpg with premium (at $4.00/gallon).  That's 9.7 cents/mile for regular and 10 cents per mile for premium.  Regular wins.  At these prices, the break even price would be a 37 mpg for regular and 40 mpg for premium, or about 8% better gas mileage with premium.  I seriously doubt that you will get 8% better gas mileage with premium.

[CaliberSRT4]

Sacred Bezel wrote

I'm not expert ( on this or much else for that matter) but the lore I read is that higher octane will give better mileage per gallon ( think about it-if you get more power per gallon then fewer gallons needed to do the same work), but not enough to make up for the difference in cost over lower octane fuels. There is a fun-factor in the pricing spread.

It is like you say, slight increase in fuel economy with premium due to the extra power, but not enough to make up for the cost increase of premium fuel.

Personally, I use nothing but premium, and that is what I would use with the Fiat 500. I prefer to have my car at optimal performance and I do enjoy the power. So while I would prefer the Abarth, if I had the regular 500 I would be wanting to make use of every bit of that 101 hp engine.

However, those that drive a lot more miles, perhaps with long commutes, might opt for regular fuel almost all the time. Especially if they usually run the car fairly easy, they could save a fair amount of money over time.

[Gavin]

I always use premium...but then I only have two scooters...one has a  2.1 gallon tank, the other has a 3.2 gallon tank...the the difference at fill up is minimal..

I'll probably drive the 500 less than 4000 miles a year (maybe a lot less--mostly a winter car and date night with the wife...other times I'll stick with scooters and bicycles...more fun and way better mileage). So I'll only fill the Prima up about once a month...again, won't be much difference in price filling it once a month.

I'll be doing 95% city driving...not sure if octane means more in city vs highway, but will likely just go premium all the time.

Gavin

(once I get my electric motorcycle this summer...and an electric Fiat 500 or electric Volvo C30 in 2013, well I will never use gas again :) )

[Giallo Edizione]

CaliberSRT4 wrote

Sacred Bezel wrote

I'm not expert ( on this or much else for that matter) but the lore I read is that higher octane will give better mileage per gallon ( think about it-if you get more power per gallon then fewer gallons needed to do the same work), but not enough to make up for the difference in cost over lower octane fuels. There is a fun-factor in the pricing spread.

It is like you say, slight increase in fuel economy with premium due to the extra power, but not enough to make up for the cost increase of premium fuel.

Personally, I use nothing but premium, and that is what I would use with the Fiat 500. I prefer to have my car at optimal performance and I do enjoy the power. So while I would prefer the Abarth, if I had the regular 500 I would be wanting to make use of every bit of that 101 hp engine.

However, those that drive a lot more miles, perhaps with long commutes, might opt for regular fuel almost all the time. Especially if they usually run the car fairly easy, they could save a fair amount of money over time.

That's the beauty of the modern flexible variable valve-timing engine that can adapt to any grade-you can drive it as an econobox or tear up the roads on premium ( or premium plus octane boost).

It will be interesting to see what the hypermilers can do in these cars. I expect to run mine with much higher tire pressure than mfg recommendation, for instance. To make up for my heavy foot.

[Minuszka]

With the Eco-Drive software we should be able to easily and accurately follow the changes in mpg with the different fuels.

[Giallo Edizione]

Minuszka wrote

With the Eco-Drive software we should be able to easily and accurately follow the changes in mpg with the different fuels.

Excellent point!

[ciddyguy]

PE#454,

Tried to comment on this, this morning but the forum was having none of it but will chime in and say, what others are saying and even Fiat says in their liturature that 91 octane is preferred but 87 will work fine too. I'd check your owner's manual for the MINI and see what it has to say. I bet it says to run premium only in it and that 87 octane is not recommended.

[Giallo Edizione]

ciddyguy wrote

PE#454,

Tried to comment on this, this morning but the forum was having none of it but will chime in and say, what others are saying and even Fiat says in their liturature that 91 octane is preferred but 87 will work fine too. I'd check your owner's manual for the MINI and see what it has to say. I bet it says to run premium only in it and that 87 octane is not recommended.

Premium only for MINI S. Especially if you've upgraded engine management system software, installed a smaller supercharger pulley etc.

[CaliberSRT4]

This is from the 2003 Mini Cooper S manual:

The engine uses lead-free gasoline only.
Required fuel:
>Premium Unleaded Gasoline,
min. 91 AKI.
AKI = Anti Knock Index

2003 is the manual that came up, but that is the same generation as PE#454's so I'm guessing the fuel requirement is the same.

[PE#454]

Thanks for all of the responses, guys. I learn so much on this forum!

Yes, the manual for my 2004 (can't remember the exact wording) said to use premium, so that's what I've gone with except that one time. And while I would love to keep my MINI, I will be using it as trade-in for the Fiat. Things I'll need to become adjusted to with the changeover: an even smaller (!) gas tank and even lower (!!) ground clearance.

[Fiat500USA]

 To get the most out of the 1.4L MultiAir use premium.  The engine is rated on this octane and will have the best performance. You can use lower octane, but you'll lose out on acceleration, etc.

The higher octane will allow the engine to use more ignition advance and that helps with acceleration, drivability and response.  You'll miss out on some of the fun continually running the low octane stuff.

Besides, on a 10 gallon tank, it's only $2 ...

[MrJones]

Fiat500USA wrote

Besides, on a 10 gallon tank, it's only $2 ...

I suppose if you're made of money you won't miss the nearly $300/year.
As far as I can tell, for most driving conditions you won't get any benefit from using premium fuel. (unless you own a lot of stock in the petroleum industry)

[unclelaverne]

I'll probably fill up once a week or so.  The difference for me will be about $10 - $12 a month.  I'm not made out of money but if $10 a month becomes a concern for me, I should think I better be taking the bus.