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What's the best fuel or mix of fuels to use?

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To use 87 or 91/93 octane?

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26K views 28 replies 14 participants last post by  Brown Irishman  
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#1 ·
I was re-reading my manual and found the section on fuels (book 3.4 Tips and advice for model year 2004, page 34-35).

The book kept using the AKI as a reference to the minimum, for lack of a better term, burn ability of the fuel. The manual calls for a minimum of 87 AKI. So I went to wikipedia and found this:

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

In most countries (including all of Europe and Australia) the "headline" octane rating, 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, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, is 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and some even deliver 98 (RON) or 100 (RON).

All the years I've had a VW that required premium gas I never knew 91 octane in Europe is equal to our 87 AKI gas. Is this really true? Back when I had my 5 valve Passat in 2001 I tried cheap gas and it ran terrible so I never tried it again, was that just a fluke? What does everyone here use?
 
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#2 ·
Run the 91/93, what ever is in your area. Guys have tried lower grade and have noticed performance loss as well as mileage being down. I run 91 in mine all the time. 93 is not available here due to something with altitude and not really needing anything that high here.
 
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#4 ·
I agree about not being cheap but I'm about to put 3300 highway miles on my Treg over vacation end of this week into next. Just wondered if I could save 10% on fuel over the trip. I'll probably try it for just one tank anyway (I'm stubborn). If I get terrible gas mileage or performance issues I'll let you all know. 10% on even this long of a trip is likely to amount to less then $30 but I don't want the oil company getting one red cent more then necessary. :mad: haha
 
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#6 ·
I agree. On my '87 GTi (8-valve 4 cylinder) I once tried 87 octane and not only did my little engine knock, it didn't have the same power. And mileage went down. Same thing applies to the current engine in my Touareg. I use only top tier gas. Here that means Chevron Supreme 91 octane. I also drive 12 miles out of my way to another station in another county that has the gas without ethanol (ethanol is mandated here from November through February). Just don't want to see my mileage drop 15% during this time. Even with gas prices at current levels, I like taking care of my engine. I also visit a couple of very good restaurants in the area near the gas station, so it's not a silly trip. I consider it a nice drive. And driving is after all, what we all enjoy. :D
 
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#7 ·
Here we only have 83/87/91.. so I go for midgrade.. I switched it up some and alternated between 87 and 91 but didn't see where it would do much difference.. I do run 91 when its wacky wednesday here and all grades are same price as 83 once a week.. that is nice but otherwise its 87. Its not being cheap..and when I run 91 I don't see any difference in mileage or performance..
 
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#8 ·
I'll try my best to keep track of the milage with different grades over the course my 3300 mile vacation and report back on the 12th when I get back to MD. The drive doesn't change much in elevations so other then temp and humidity there shouldn't be too many other variables.

Happy New Years!
 
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#9 ·
Just thought I'd mention this from the latest vw magazine,using less than the required octane gas,May lead to premature engine damage and wear,and decreased engine performance.It's up to you to decide.
 
#10 ·
I dont think its worth the risk to routinely use lower octane when 91/93 is recommended so I use the highest grade available here in Colorado but FWIW....

This summer while pulling my Airstream to Minnesota I ran through areas of the country where 91 octane wasn't available, only 87 and 89. When I ran 89 octane I noticed an increase in my gas mileage while towing. This may be attributed to the difference in towing at 6000' feet in Colorado vs. sea level but there was no engine knock or decrease in performance.
 
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#12 ·
Okay, just incase anyone's interested, I just returned home after driving over 3,300 miles in my V8 from Maryland to Atlanta to New Orleans, to San Antonio, to Memphis & Nashville, to Smokey Mtns, and finally back to Maryland.

I kept a log with, average speed, mileage per fill, brand, grade, reported MPGs (in MFI), ambient temperature, and if the refuel included a cold start. I made a mental note of the altitude but as it never made a noticabe difference I didn't annotate it. The altitudes I drove in ranged from 0' - 2500' but probably averaged around 500' - 700'

Overall I got 16.7 MPGs at an average speed of ~67 MPH. After reviewing the data, what I found surprised me. No single factor effected the mileage more then the brand of gas. Grade, ambient temperature, and cold starts had little to do with the overall MPGs as compared with the brand of gas. In some places, Alabama for example, running premium gas returned less then 16 MPGs where as some where North Texas I filled up with Marathon 89 and got a little over 18 MPGs. I found marathon, Shell, and BP to be the best fuels returning at least 18 MPGs on the hwy. Shell 89/93 blended returned about 19 MPGs in Tenn in >2,000 altitude.

I will be switching to Shell or BP (available in my area) after this analysis from Costco.
Cheers
 
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#13 ·
That is interesting data. I use Chevron, and find that the consistency is very good (milage and the smoothness of the car), but to have done a test like this to find out what works and what doesn't work. Was there a significant difference in price per gallon from Shell to some of the fuels that didn't perform well?
 
#14 ·
Also, don't forget there could be variances for weather, traffic and terrain. All are very hard to compensate for when doing tests like this to ensure that you are comparing apples to apples.

As for me, it's 91-proof Chevron all the way.

Matt
 
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#15 ·
I didn't have a chance to try Chevron. It's funny that both Vegas Matt and NorthVan997C2S mentioned that as I thought about Chevron specifically over my trip but didn't have an opportunity to try them out. The premium (in terms of $$$) on premium at Shell or BP will be worth it. When I'm home I always use Costco gas (93), the results are always fluctuating which I attributed to the 20-25 degree temperature swings here in MD this time of year. Now I know you get what you pay for and the 15% more at the pump for shell will pan out as I get >18 MPGs vs. the <17MPGs from Costco or other generic station.

On a side note I mentioned this little side activity to a co-worker, he's kind of geeky like I am when it comes to this sort of thing. He was interested in my findings and told me a story of a fuel delivery guy he once chatted with. To make a long story short, the delivery guy told him fuel trucks never return gas to the plant and if there's too much of one octane they simply put it in what ever tank at the station that has room! That means you could be buying 93 octane and getting a mix of some lower grade, or buying 87 octane and getting something of a better grade! I'm not sure how credible this is but seems like it'd be the easy thing to do if you're a trucker, anyone else heard of this?

For Vegas Matt, I paid close attention to temperature and even made that part of my table, Altitude is another story. On the way to Texas it as an even altitude, started out >200 ft. peaked at around 500 ft. and down to 0' (New Orleans). In each tank of gas I made mental note of the altitude and didn't find it to be a significant factor (i.e. less then 1%). On the return trip home I actually achieved higher averages in Tennessee which is odd because it's a higher elevation 1,000' - 2,500' and has plenty of hills, then again this is the region I chose to start using top tier MFGs like Shell and BP.
 
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#17 ·
safford1977 said:
To make a long story short, the delivery guy told him fuel trucks never return gas to the plant and if there's too much of one octane they simply put it in what ever tank at the station that has room! That means you could be buying 93 octane and getting a mix of some lower grade, or buying 87 octane and getting something of a better grade! I'm not sure how credible this is but seems like it'd be the easy thing to do if you're a trucker, anyone else heard of this?
Click to expand...
I am in the gas business, and I want to make sure that everyone here is educated, since many have educated me.

Most fueling companies do not have a "plant" to go back to, meaning they are just a transport company. It would be true that they would drop excess gas in another tank should they have it. But this very rarely happens, the drivers and dispatchers know what they are doing and how large the tanks are. Most stations have 10 or 12 thousand gallon tanks and only order 8 thousand gallons at a time, so room is typically not an issue. If excess gas is put into another tank, it should always make the octane higher. Meaning putting 93 octane into the 89 octane tank, or 89 octane into the 87 tank. This is regulated by the Dept of Natural Resources and checked on a random date monthly or quarterly. If they octane rating is below the sticker, there is a fine and the station is shut down until the octane rating has been raised, and rechecked. Not worth the trouble. I could get into further detail, but if you need or want to know more PM me I will help where I can.

On the CostCo or Sams Club gas. Let me start by saying that I have bought product from them before, but I tend to use Branded stations. By Branded I mean, BP, Shell, Cheveron, Pure, Sunoco, etc. Costco and Sams Club, are known as unbranded dealers. Meaning they can get gas from anywhere they choose. Sometimes it could be from one of those brands, but sometimes it might not. They tend to find whatever is cheapest that particular day and buy that. It could be that they are buying a non top tier gas. Just food for thought, and remember in most cases you get what you pay for.
 
#18 ·
Question: why is 89/91 midgrade (or so..I've seen 85.5 low-88-mid-and 91.something as high at the fuel stations in wyoming etc on this last trip..weird) cheaper in lets say Montana, Wyoming, South/North Dakota?? the low grade was like $1.45 mid was $1.40 and high was $1.75 or even a greater almost $1 difference between mid and high test.. it was something else to see this out west
 
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#19 ·
If I understand your question correctly, different states have different tax rates, also sales tax in counties and cities will also come into play when figuring out gas prices.

On the other matter, it is quite rare to see midgrade prices lower than regular prices. 85.5 Octane is quite low, I would guess it is a specialty fuel.
 
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#20 ·
VWZach,
Thanks for the FYI, what you said makes perfect sense. Just wish there was a better way of being sure what you get at the pump. Do you know of any case where a branded station, i.e. Exxon, get's non-branded gas? The two Exxons by the Costco I go to always sell gas for a penny or two above Costco which is at least $.15-.20 lower then anywhere else. I also noted inconsistent results using Exxon's gas there.

Update on the BP gas:
I finished off the tank off the tank of BP gas with me driving to and from work. The temps here in MD have been hovering around 37/38 in the day and about 20 degrees cooler at night. Driving to work yesterday my oil gauge was pegged the whole time, she never fully warmed up, under these conditions I got about 10.5 MPGs for the past three days using BP premium according to the MFI. I know I said I was going to Shell to fill up next but it wasn't convenient this time as I happened to be at Costco so I filled up there with 93. At least according to the MFI, I got 13.8 under very similar conditions with the Costco gas.
 
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#22 ·
safford1977 said:
VWZach,
Thanks for the FYI, what you said makes perfect sense. Just wish there was a better way of being sure what you get at the pump. Do you know of any case where a branded station, i.e. Exxon, get's non-branded gas? The two Exxons by the Costco I go to always sell gas for a penny or two above Costco which is at least $.15-.20 lower then anywhere else. I also noted inconsistent results using Exxon's gas there.
Click to expand...
Branded Stations have to buy 90% of stock as a branded product. Most stations buy 100% unless there is some sort of shortage (as happened in the SE this summer). The Exxon near the Costco knows that most consumers do not care what brand it is as long as it runs, and is cheap. So that is why they stay a couple of cents higher. If they were too much higher no one would buy it there.

I will agree with snwskier, most branded fuels only have added tracers and detergents in it, but there is a reason they are branded. The US does regulate fuel to a high standard, so all fuel is going to be okay, but different brands seem to run better in different cars. Just like some oils are higher quality, yet they are all regulated. It is the same sort of thing.

I only run 92/93. It is not worth the risk in my opinion to save a couple of bucks. The difference in premium and regular is 30 cents here in ATL. Again, not worth the risk.
 
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#21 ·
I use high octane over lower octane because of simple math. At $2.00/gal high octane fuel is worth the extra $6 or so over the 87 Octane fuel. I understand that gas prices are different everywhere you go, but the difference between 87 octane and 93+ is measured in cents, typically $.20 in my area. Also, where you get gas is not necessarily a major problem either. Fuel is refined and distributed under strict guidelines so whether you go to Chevron or 7-11 the fuel is the same minus the small percentage of detergents added to the fuel (such as TECHRON). I do understand that there is a stigma about where people choose to fuel up their vehicles and that is fine, but if you are going to pay $.50-$1 more because of name brand fuel than that is your choice.

In summary:

Use high octane fuel from wherever you choose, as long as it is a place that gets regular deliveries.
 
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#23 ·
snwskier01 said:
In summary:

Use high octane fuel from wherever you choose, as long as it is a place that gets regular deliveries.
Click to expand...
Not sure if you read the whole post but in short I tried several methods on a recent trip spanning >3300 miles. More then any other factor I found the place you get your fuel is the biggest dependency on how much MPGs you get.

For example, when I was in Alabama, I filled up with Premium only to get lower mileage then when I had filled up in GA with 87, about 15 MPG vs. 16 MPG respectively. So I paid more and got less. The Station in GA was a generic and the station in Alabama was Costco - also a generic. Both situations were on the highway, relatively same elevation, same driver - I used cruise control, no cold starts, Alabama was about 15 degrees warmer but in other areas down South I got >18 MPG.
 
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#24 ·
saff,
First of all, good work on your log & posts.
Second - did you track blends (ethanol/oxygenated fuels) or urban/rural MPG?

I ask since the formulations are quite different (esp Atlanta - it's got it's own blends), and I'm wondering if/what impact that would have on mileage...

J

PS - I "blend" in the tank - at every 1/2 tank switch between "mid" and "premium" on both VWs.
 
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#26 ·
2VWatatime,

Thanks for the recognition. It really was like a bit of work to remember every time to get the log out and write everything down. I was on vacation and each time I felt like I was rushing to do the log. Anyway, hope there's some pay off for more then just myself - hence the posting.

I didn't track Ethanol, but was aware of that as an issue. Most stations have a sticker that states "MAY contain 10%..." so I had no way to determine if the gas did or didn't.


RE your PS. I had the best results, >19 MPG, on blending Shell. I filled ~1/2 the tank with 89, turned the pump off, filled up the other ~1/2 with 93 so the blend was from the same station. As I drove the mileage went up quick watching the MFI as opposed to other brands which went up slowly and steadied out over the course of the first ~100 miles or so.
 
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#29 ·
I only use the best available 91 to 93. I've kept track of mpg with gas that I knew contained ethanol and others that didn't. I loose at least 2 mpg with ethanol. I average about 12 mpg on ethanol blend and up to about 15 on non ethanol blends. I have an 04 V6 with heavy mud tires and a heavier right foot.
 
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