Fuel Grades vs. MPG

[Drew2000]

Originally Posted By: Big O Dave
Originally Posted By: tom slick
do you normally use shell gas?


Exactly what I was thinking... all grades of Shell have the same additive levels - only the octane is different.

This is true of all Top Tier gasolines, BTW.


Not quite true...

"Shell Regular and Plus gasolines, which meet the “TOP TIER” standard, also contain more than two times the amount of cleaning agents required by the EPA. Shell V-Power goes even further – it has more than five times the minimum amount of cleaning agents required by government standards and twice the cleaning agents required by the “TOP TIER” standard."

http://www.shell.us/home/content/usa/pro..._standards.html

 

[Drew2000]

http://www.theautochannel.com/news/2006/05/09/006142.html


“It’s a feel good thing,” says Pete Misangyi, Fuels and Lubricants Engineering Supervisor for Ford Motor Company. “People feel that they’re getting better fuel economy or a cleaner fuel by using premium. But unless you’re having a knock issue, then premium usually has no added value.”

In fact, Ford’s 2006 Model Year Fuel Recommendation Guide notes if your vehicle is experiencing starting, rough idle or hesitation problems, premium unleaded may cause the problems to become more pronounced.

“Some premiums are less volatile and don’t vaporize as well in a cold engine during start-up,” says Misangyi. “You will see some hesitation.”

You should also be sure that you are getting what you are paying for at the pump. Misangyi says the Environmental Protection Agency requires that all gasoline be certified with a minimum detergent level, but there are loopholes in the process.

Oil companies submit test results on a generic gasoline to the EPA for certification. But while the pump gas is supposed to perform at least as well as what was certified, there’s no assurance that the fuel does.

Ford recommends BP fuel for all of its 2006 Ford-branded vehicles. BP is among the companies who routinely test their base gasoline, making sure that their gasoline has the same detergency performance as originally certified.

Since industry standards don’t guarantee it, “Look for brands that promote good detergency,” says Misangyi. “The ones who state it, are probably doing it right.”

You probably don't need to be spending on any aftermarket cleaning products either. Ford’s Owner Guide notes it should not be necessary to add any aftermarket cleaning products to your fuel tank as long as you continue to use the fuel and octane rating recommended by the manufacturer.

“If customers need an additive due to engine deposits, or bring the vehicle in for service due to a performance deficiency, they should probably switch the brand of gasoline they’re using,” says Misangyi. "A clean engine provides better fuel economy".

Misangyi reminds consumers to always check the owner’s manual for proper fuel information such as octane recommendations

 

[sparkplug]

Originally Posted By: blackdiamond
I would argue that women GENERALLY don't pay as much attention to their driving (men have one track minds) and as a result are less smooth which yields less mpg. Another physiological fact is that women GENERALLY have poorer depth perception making it more difficult for them to adjust to speed changes. They also have faster reactions times to even things out. Also, many of the ladies that ARE interested in cars tend to drive agressively so they either drive fast or don't care.

I actually use the trip computer as a form of entertainment when I drive, my wife NEVER does this.


This is true. My g/f has two speed modes. Metal to the asphalt or ABS lock up. Rarely in between. Constantly swerving because shes not paying attention to the road and looking at horses. Somehow her Cobalt gets 30mpgs. It's fun to rid with her.

 

[blackdiamond]

Tank 1: 16.9 mpg calculated. This is about 1 mpg higher than the overall average since I've owned the Sequoia, but there have been other tanks at, or near, this level in the past. Too soon to really tell anything.

Note: The mpg dropped a bit with the new tires so this tank put me at or above where it was before so I've got multiple things to consider and compare.

 

[blackdiamond]

Tank 1: 16.9 mpg
Tank 2: 16.7 mpg

Both tanks are the highest that have been achieved with the new tires, but so far not enough difference to justify the cost.

 

[JHZR2]

Im going on a long, slow drive tomorrow, so I filled up my saab with 87 octane gas. I figured that I might as well do an experiment and save a few pennies.

My car is designed to optimize spark, timing, etc. with an advance up to being able to take advantage of 90 octane gasoline. Typically I fill up with 89, and sometimes get 91 if it is a good deal at sunoco. Rarely will I buy 93, which is the typical premium gas here.

OK, so I went from a solid 89 octane to 87, my tank was nearly empty. General cruising, according to my scangauge, my ignition is at 33-34 degrees, as I recall. On 87, I am noticing it only goes to 26-27.

My spark plugs are nearly at end of life according to the service manual for my car. This may have some effect, but the fuel will obviously have moreso.

What does this mean in terms of MPG? Well, I did an oil change to GC, and am seeing an economy drop. Ive only run a few tanks, so it will be tough to discern the difference between the oil and the fuel, but we will see what I can find out...

 

[Benzadmiral]

So far, no improvement on 89 octane. I haven't gassed up in about 9 days, I've driven just over 200 miles, and the gas gauge, that lying robot, says I've used just over 1/2 tank -- the same consumption as I get on 87. I'll gas up in a day or two and report again.

 

[blackdiamond]

Yesterday, I drove from near Seattle, WA to Portland, OR to an air show and was hopeful to get a good clean highway run on the premium grade fuel, but I got stuck in traffic (under 10 miles in 1.5 hours) so I didn't see the results I was looking for. After 4 or 5 tanks I'm convinced that the improvement is minimal at best and certainly doesn't offset the cost. I'll post some more detailed numbers later.

I had my wife fill up with regular grade fuel today so I can get another baseline before switching to GC in about 1,500 miles. I expect I'll see slightly improved mpg than before since my wife is being more careful with her driving.

 

[RacerE7773]

I've read and been told that 95% of the vehicles on the road use 87 octane. The few times I'd gone above that I never noticed any difference, so in winter I mainly add a drier every so often and a ijector cleaner at end of the winter (seems to be around June here in Ohio).

 

[Benzadmiral]

Originally Posted By: Benzadmiral
So far, no improvement on 89 octane. I haven't gassed up in about 9 days, I've driven just over 200 miles, and the gas gauge, that lying robot, says I've used just over 1/2 tank -- the same consumption as I get on 87. I'll gas up in a day or two and report again.

Results yesterday from my 89 octane run: abysmal, possibly because I've been using the A/C more. Calculation yielded 20.57 mpg over 12 days . . . yet I saw over 21 a number of times this summer with the same driving pattern and A/C use.

I think 87 will be the Buick's feed from now on.

 

[CivicFan]

I have been trying to gauge the fuel consumption for the wife's BMW Z4. The recommended octane rating is 91. I always use Shell gas.

When I run a 50-50 mix of 93 and 89 (yielding 91 octane since I haven't seen Shell gas stations selling 91 octane here) I get about 32 mpg on highway. On 93 octane, the mileage drops to 29.8 for similar driving.

This is according to the mpg meter in the car. So far, I think higher octane actually harms the gas mileage.

 

[blackdiamond]

The unscientific results are in. I broke my records down into several catagories for a better comparison:

87 Octane / Conventional Oil / Old Tires = 15.24 mpg (6 tanks)
87 Octane / Synthetic Oil / Old Tires = 16.11 mpg (7 tanks)
87 Octane / Synthetic Oil / New Tires = 15.94 mpg (5 tanks)
91 Octane / Synthetic Oil / New Tires = 16.70 mpg (4 tanks)

Keep in mind that my wifes work commute greatly increased in highway miles somewhere in the tire change and I think the mileage probably went down in reality. I'm not claiming that the driving was equal for each group, but the 87 vs. 91 overall comparison is 15.8 vs. 16.7 mpg. This is 64% of the required improvement to cover cost.

I'll run 87 for a while until I get some stable readings and then I'm going to GC oil and will see if I note any difference. I may play with 89 at some point in the future as the butt-o-meter liked the 91 octane, but not enough to justify the cost. I need to calculate the actual cost increase...

 

[Benzadmiral]

I went back to 87 when I gassed up on 9/3. Result yesterday, 21.996 mpg, with the usual frequent A/C use, but one more 24-mile highway round trip than usual. I might try a tank of 93 just for giggles, but I'm pretty sure I'd be wasting my dough with anything other than 87.

 

[wavinwayne]

My '00 GTI 1.8T gets pretty much identical fuel mileage, regardless of which octane fuel I use. There may be a little difference, but IMO it falls into the "statistical noise" category.

 

[blackdiamond]

I've now run three tanks on regular fuel and compared to the four tanks of premium I've seen a 1.0 mpg loss. Not quite enough to justify the price of premium, but enough to make me consider giving mid-grade a shot at some point.

 

[TexasHonda]

There's another source of bias that you would be desirable eliminate. When you know you are using 87 or 91 grade, you may subtly alter your driving technique. This is not conscious, but is unavoidable if you know what fuel is in the tank. To avoid most bias, you will need to drive the car w/o knowledge of what's in the tank. Perhaps your wife buys the gas w/o your knowledge for your driving time? Ideally, it would be preferable to have a double blind where both you and your re-fueler don't know what grade of gas is being loaded.

Experiments of this sort are very difficult. I've tried my own experiements and concluded I may be biasing the results w/ lighter throttle pressure and small changes in driving procedures.

Interesting but not very scientific is best you can do.

good luck

 

[OVERKILL]

FWIW, Shell V-Power states that it has no ethanol in it, this is right on the pump. That's reason enough for me to use it

 

[lexus114]

Originally Posted By: OVERK1LL
FWIW, Shell V-Power states that it has no ethanol in it, this is right on the pump. That's reason enough for me to use it

Dont you just love the way the EPA shoves things down our throats?? (meaning this ethonal [censored] etc.)

 

[blackdiamond]

Originally Posted By: TexasHonda
Experiments of this sort are very difficult. I've tried my own experiements and concluded I may be biasing the results w/ lighter throttle pressure and small changes in driving procedures.


My wife fills the tank (with whatever brand and grade I request) the majority of the time and does 90% of the driving. She did start being more careful about MPG when we started the premium run, but it was more related to trying to match my MPG and not the grade of fuel. I'm positive that she doesn't drive with the fuel grade in mind, but I could be guilty of it for sure. I'm not sure her run for better MPG even made it an entire tank. Her attention span isn't significant in general, so automotive related things have little chance of being tampered with.

 

[Benzadmiral]

I'm (reasonably) sure I didn't drive any harder when I had the tank of 89, or any easier the following week when I went back to 87 -- so that's an unlikely reason for my low mpg with the mid-grade, and higher (i.e., normal) mpg with the regular. My commute and weekend errands are pretty much the same week to week, and there were no major traffic blockages or other worrisome things.