Premium gas? Facts & Myths

[steelwind101]

It seems like in the USA you have fuels with much lower octane ratings then we do in UK. You can easily find fuel with an octane rating of 99 on supermarket forecourts.

With in certain parameters you will find engines adjust for inconsistancy etc. I have also noted however, in the USA many EU cars and even Japanese engines have less out put then they do on the same UK or European model.

I think many companies take the fuel issue in to account and seem to tune engines/ecu's accordingly.

There are a few which i have seen where its the same power and they do stress, "premium fuel only" during my visits to the USA.

Geoff

[rjstaaf]

Originally Posted by steelwind101

It seems like in the USA you have fuels with much lower octane ratings then we do in UK. You can easily find fuel with an octane rating of 99 on supermarket forecourts.

With in certain parameters you will find engines adjust for inconsistancy etc. I have also noted however, in the USA many EU cars and even Japanese engines have less out put then they do on the same UK or European model.

I think many companies take the fuel issue in to account and seem to tune engines/ecu's accordingly.

There are a few which i have seen where its the same power and they do stress, "premium fuel only" during my visits to the USA.

Geoff

In the US we use an average between RON and MON rather than the more typical straight RON measurement which is what most of the world uses. This makes our octane ratings seem lower...

Octane rating - Wikipedia, the free encyclopedia

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).

[lawrencea]

Ive tried 87,89,and93 octane on my car and I didnt notice any difference, so I just use 87. I do have a 4 cylinder, so it shouldnt need higher octand gas. But what I did notice was a difference between brands of gas. I seem to get 1 more mile to a gallon with Shell then BP. Does anybody know anything about Marathon gas? Is there any more gasoline that is Top Tier?

[2000firebird]

all i see here is COST of premium as if its some huge expense... think about your average gas tank.. 15 gallons? on average i find midgrade always 10 cents more, and premium 10 cents more than that. so 20 cents more per gallon for premium.. lets say you fill up 10 gallons. so 2 dollars more you're getting premium, is it really that much of an expense, two bucks a week.

the purpose of a octane rating is just to tell you how well it can handle detonation. if you're not getting detonation with a lower octane then theres no point in using a higher one

[99blackSE]

I would just follow the owners manual, they built the thing so they probably know what's best for it.

However, with sleds and carbs, 91 all the way. I never run anything lower than that in our Ski-doo.

[paul34]

Originally Posted by steelwind101

It seems like in the USA you have fuels with much lower octane ratings then we do in UK. You can easily find fuel with an octane rating of 99 on supermarket forecourts.

With in certain parameters you will find engines adjust for inconsistancy etc. I have also noted however, in the USA many EU cars and even Japanese engines have less out put then they do on the same UK or European model.

I think you'll find both issues are resolved when you take into account measurement methods

As rjstaff pointed out, we use a different method of rating octane, making ours appear lower.

In the UK, its not uncommon to state engine output in bhp, which often shows up as a larger number than SAE horsepower, which is what we use in the US.

[CV_Soccer]

After breaking in my 06 GTI I did a blind test of 5 tanks of Regular, Mid-Grade, and Premium keeping track of MPG and general performance. I had a lot of funny looks when I pulled in to fill up and asked for help in selecting the type of gas.

Conditions of the test

1. Tire pressure was checked weekly, and adjusted when needed.
2. In diving to an from work I used ‘Cruise Control’ as much as I could to limit the human factor.
3. My driving was to and from work which is 58 miles round trip.

After 15 tanks which took almost 4 months of driving here is what I found

1. On regular I averaged 28.5 MPG and noted a slight drop in engine performance
2. On Mid-Grade I averaged 31.1 and noted almost no difference engine performance
3. On Premium I averaged 31.5 and the acceleration was spot on.

When I took into account the cost difference between Regular and Premium it was cheaper per mile driven using premium so long as the cost difference was not greater then 24 cents per gallon. When I include Mid-Grade the clear winner in the best cost per mile driven s this one.

VW tells me that Premium best for my car but at $3.59 and Mid-Grade at $3.49 well you can do the math.

My baby likes to run but having the very little extra in the wallet when you get there isn’t all that bad either.

[itb76]

Originally Posted by lawrencea

Is there any more gasoline that is Top Tier?

Top Tier Gasoline

[Aurora40]

Originally Posted by 32VDOHC

Pre ignition which is the cause of the knocking sound in a engine under a strain, does not happen while using premium fuel. This pre ignition reduces power and fuel mileage.
If the car does not call for it, consider yourself lucky.

Pre-ignition happens when the fuel ignites on it's own before the spark fires. This is pretty much catastrophic to an engine.

That is not the light pinging sound that some engines make, that is called detonation. Newer cars with sensitive knock sensors, they can detect such small detonation and adjust that you'd likely never hear it at all.

My two cents. You need how much octane you need. More is a waste. If you want to find out how much you need, put some gas in the tank, hook up a scan tool, and go drive the car hard. If there is no knock retard, you don't need more octane. If there is, maybe you do. If you don't care about wasting it, put in premium and enjoy.

If you want to keep your engine clean, as said, use a Top Tier gasoline. This way you know that even the lesser octanes still have an acceptable amount of additives in them to keep your fuel system clean.

I often put in 87 octane when going on long trips because I can burn through a tank or two without ever going to wide-open throttle. Even an engine that needs more octane doesn't need it at low throttle operation.

[johnand]

Your friends new C300 is tuned for premium, but is also a flex-fuel vehicle that can run on E85. Since it is flex fuel it is even more important to run premium in it, since it has little room for adjustment for lower then 91 octane. That engine is very high compression (11.3:1), and requires premium period. In fact, the manual states engine damage caused by running lower than 91 octane is NOT covered by Mercedes Benz warranty.

[01TrublUGT]

Originally Posted by johnand

Your friends new C300 is tuned for premium, but is also a flex-fuel vehicle that can run on E85. Since it is flex fuel it is even more important to run premium in it, since it has little room for adjustment for lower then 91 octane. That engine is very high compression (11.3:1), and requires premium period. In fact, the manual states engine damage caused by running lower than 91 octane is NOT covered by Mercedes Benz warranty.

Exactly, running lower than 91 octane will void warranty.

I think alot of people who have FFV are confused by the way they name it E85 does not mean 85 octane, that stuff is more along the lines of 105 octane. Have seen some forced induction cars converted and pick up an extra 40-50hp by running E85 as they are able to bump the timming up more than what the 93 would allow them to do.

[kittay]

I run E85 in the summer and 93 in the winter. My cars are all turbo'd so they cannot run anything less then 91