sri_gondi

Folks,

I have read some where in the forum that our RL might not actually need 93 Octane but would be sufficient if we use 91Octane(Sunoco). Did anyone use this fuel and observed any change in performance and consumption. I am using 93 Octane from Mobil all the time and I would like to switch to Sunoco if 91 is okay to our RL.

I have just crossed 1K in new RL and I can never ever ever have bought a better car than this Damn Good CAR...............


Input please.

GoHawks

The RL requires 91 Octane, not 93. The issue is that many gas stations Exxon/Mobil, BP, Shell, etc. offer 89 (mid-grade), and 93. I guess you can mix half mid grade half premium, and I believe I read somewhere that it would work, but you're really not saving all that much.

Assuming the price difference between mid-grade and premium is $0.15, and assuming you're filling up a completely empty tank (19 gallons), putting half mid-grade would net you a savings of approximately $1.27 per fill-up $0.15 * 9.5 gallons.

Savings are obviously less if the price difference between the two grades is less.

Mike_TX

You will notice NO difference between 91 and 93 octane, and 91 is fine.
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nmariani

I have often noticed that some gas stations have more of an impact on the "range meter" than others. For example, if I go with Chevron 91, the MID range reads about 485 miles or so. With Shell v-power 91 it's a bit less, or 460. With Valero or BP it's goes to over 500 miles. I have also noticed a slight difference between the gasoline here in California, and that of fuel in Nevada, Arizona, or other areas.

In each instance I would always fill the tank completely from nearly empty, or about 17 gallons of premium. How does the car account for these differences in mileage? Does it have a way of knowing the TYPE of fuel you are using somehow?

Mike_TX

No, the car has no idea what has just been pumped into it.

I think what's happening is that the specific gravity of the fuel is affecting the float level just a bit, sending a slightly different message to the computer. A fuel with a lower specific gravity might not raise the float as much as a denser fuel (higher SG).

The fuel with the lower SG is probably a bit more volatile, though, and should therefore vaporize more readily and burn a little more efficiently, so it all works out.

One thing to remember is that the SG of any almost fluid is affected by temperature, so that fuel in Nevada may have a lower SG just due to higher temperature (for example). Another thing is that many states and municipalities have mandated use of ethanols, oxygenates and other additives that affect the SG.
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sri_gondi

It is not the question of saving any money GOHAWKS...It is just about getting good knowledge about the behaviour of RL and how it recieves 91 grade.Anyways thanks for the suggestions though. I would better stick with Mobil 93 grade. To some's extent I feel Mobil's gas is little bit superior than Sunoco's gas. Isn't that true?

Ernie Golfs

I've never seen 93 octane in California. My RL has survived on 91 for over 20 months and does just fine.

sab35263

California oil refineries have stopped making 93 octane gas since 2000. Just because they are thieves and they are charging us an arm and a leg for a gallon of gas here because its California. But 93 octane is great and you will see better gas mileage with the 93 octane.
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Meteor06RL

At nearly all stations here in DC, the selection is 87, 89, and 93. Only Sunoco has 91 and it isn't really any cheaper than most other stations' 93.

synth19

I only use racing gas. jk.... 93 is the norm here as far as the premium fuel goes. I use 93 octane from Mobil, performs the best imo.

Mike_TX

Okay, maybe it's time to discuss this again.

If you are anywhere near a fuel terminal (I am), you can watch a half-dozen different brands of gasoline tankers lining up to get gasoline from the same pipeline. Shell, Exxon, Mobil, Valero, BP, etc., etc. all get their gas from the same "spigot".

What's even MORE exciting is to occasionally see a Shell tanker filling the underground tanks at a Texaco station. (They try to be discreet about this, but I've actually seen it. )

Yes, some tankers get their fuel direct from the refinery, where it makes more sense to do so. But it's also a fact that refineries swap gasoline. If Texaco has a refinery in Houston and BP has one in Mississippi, it makes a lot more sense for the BP stations in Texas to get gas from the Houston (Texaco) refinery than to truck it all the way from Mississippi. And vice-versa. The bottom line is that gas is gas.

What makes Shell gas different from Exxon and Texaco gas is their additives. Those additives are often added right at the terminal. An additive packet is simply dumped in with the "base' gasoline when the tanker is loaded and it mixes as the truck sloshes along on its way to the service station in your neighborhood.

Both crude oil and gasoline are commodities and are freely traded on the world market and among the various brands. Chemically speaking, there's nothing essentially different about the base gasoline one brand or the other uses. You just have to decide whether you like the additive package a particular brand touts ... or who has the best TV commercials.
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GoHawks

I just pointed out the cost due to the fact that 93 octane may be more than what is needed, but the cost savings are minimal if you want to bring it down to 91.

I have no scientific proof, but I tend to believe Mobil, BP, and Shell (major brands in the Chicago area) have the better fuels. I usually will fill up with either Mobil or BP.

getakey

I have not tried this on my RL, but I use to track the mpg on my Durango (V8) every fill-up. I tested the different grades and would consistently get at least 10% better mpg with 89 versus 87. Couldn't really brag about the mpg in either case, but 14.5 was clearly better than 13. So, if the price difference was less than 10% between these grades (and these days its always less than 10%), I always filled up with the 89.

nmariani

Hahaha... That's funny, but yes, true....

A friend of mine said he actually witnessed an Arco truck filling the tanks at a Chevron station here in the Bay Area once. He said they usually do it in the middle of the night when less people would notice...

Now, that would definitely be a kodak moment! I'd give anything to get a picture of that!

Even so, it still seems that some gas is "better" than others, especially when you compare our California gas to that in other states. I routinely travel out of state in my RL, and find that I get slightly better mileage (about 2-3 MPG) when filling up in Reno or Phoenix than in say LA, or SF. It must have to do with all the additives and the special air quality crap they mix in with our gas here.

Under idea conditions, and assuming fairly flat terrain, I can get as much as 450 miles to a fillup. I can easily fill up here in San Jose, and drive to San Diego and still have about a quarter of a tank left over after I arrive there. That's pretty darn good for my RL.

Mike_TX

Oh, you're undoubtedly right. Here in the Dallas/Ft. Worth area, the EPA has decreed we have to use oxygenated gasoline because we used to have fairly high air pollution levels. That gas robs almost 10% of your mileage simply because it doesn't burn as efficiently.

When we travel, the second tank (after getting well outside our area) is almost always about 2mpg better than that first tank of oxygenated gas. The debate, BTW, is whether the oxygenated crap is actually 10% cleaner burning, since people use roughly 10% more of it. If it's not, the extra gas usage is cancelling out the "benefit".
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static808

I was low on gas, 0 mile remaining, on the mile range, good thing we have a reserve. I had to get regular (87 octane), no plus or premium. It was cheap, $1.88/gallon. Not sure what gas mileage I'll get though.. The fill-up was 17.3 gallons...

Chas2

I never really noticed that Sunoco sells 91 vs 93. Our local Mobil changed to a Sunoco, and it is consistently less expensive than the nearby Exxons, or Shells, but I never noticed they reduced the octane by 2 points. Makes me wonder if Costco is also 91?

synth19

My tuner prefers Mobil. He gets the BEST results when dyno tuning cars using mobil 93 octane.

lausy

I am thinking it has more to do with what the average MPG you got on the last tank before you filled up the tank. IE if you averaged 25 MPG on the last tank, the MID may show 500 mile range after fill up. If you averaged 24 MPG on the last tank, the MID may show 450 mile range.

I have used 91 and 93 octane and haven't noticed any difference in gas mileage or performance.

nmariani

No, in my tests I made sure to verify that the mileage display reads '---' and also reset the mpg by going to that option on the MID, then holding down the selector button. This should clear/reset the mpg calc. and start over.

Perhaps the density or slight formulation differences exist between different brands of gas: ie: Chevron, Shell, BP, Arco, Costco/Independents, etc. In each case I noticed consistent results which mileage range was different depending on where I went. I know that the car has no way of knowing what was pumped in it, as Mike_TX previously pointed out, but you wonder what is causing these differences.

I typically see much higher mileages on the MID after a fill up in nearly any station outside California. Last week I filled by in Vacaville, CA at Chevron along I-80. After fill-up there, the range said '480' I then proceeded east and didn't fill up again until I was in Elko, NV. I stopped at a Shell and observed the range this time at '511'!

By the time I got into SLC, then down to Vegas, I was hitting stations well above the "500" range, rarely if ever seen in California. When I got to Bakersfield, it was back to about 480!

Also, on a related note, does anyone here know about how much fuel is remaining in the tank when the MID shows '0' mile range? I think the tank size is 19.3 gal.

Thanks.

kmcheney

Several car manufacturers, including BMW, Toyota, and Honda have suggested the use of gasolines they consider "Top Tier". These fuels have been tested and are recommended because they contain the necessary additives to keep the engine running clean and efficiently. The gasoline retailers they consider to meet these standards are:

TOP TIER Gasoline Retailers:

QuikTrip
Chevron
Conoco
Phillips
76
Shell
Entec Stations
MFA Oil Company
Kwik Trip/Kwik Star
The Somerset Refinery, Inc.
Chevron-Canada
Aloha Petroleum
Tri-Par Oil Company
Shell-Canada
Texaco
Petro-Canada

You can read about this at http://www.toptiergas.com/

neuronbob

Thanks for the list. I wasn't aware of this attempt at standardization.

BP/Amoco, the gas I've used for years, is not yet on the list.

Likely hasn't been tested yet.

Chas2

Interesting that the largest oil company, Exxon Mobil is not on the list!

lausy

I have another theory. I have noticed that the pumps in CA are a little different. Most nozzles I have seen have an extra long black tubing around the nozzle making it harder to insert it into the filler neck. That extra black tubing may cause a better seal with the filler neck and less air getting in causing the fuel to go down the filler neck slower (vaccuum effect). That variance may cause the auto shut off to click off sooner and thus a little less gas goes in and therefore, lower range. I think I am putting too much thought into this!
I still think it is related with the gas mileage you getting on the current tank prior to filling up. The higher that mileage is, the higher the range the next tank full will be.

TSX69

If it matters, BP is the fuel that Ford recommends for their vehicles.

This Top Tier Gas has been around for a while so I doubt that they have yet to test BP but who knows ...