87 vs 93: The Showdown.

[Swordsmith]

The on board mpg calculator isn't
terribly accurate, better plan is to do the math by hand. Also since pump shutoff point tends to vary a little, the average of several tanks is more accurate than any single tank.

 

[GeneralZod]

I did a small experiment. I ran a few tanks in a row of 87 and my mpg dropped big time. Last tank I went with 91 and netted 35.1 verses 32-33...


I am going back to cycling a tank of 91 per tank of 87. The difference is just too great to drive using 87 straight.

 

[mitdr774]

Why not just run mid grade then? You essentially averaging it out to mid grade by running one tank of 87 and then one tank of 91.

 

[GeneralZod]

The price of mid-grade does not justify, and is not offered at Costco where I get gas.

So using some mental algebra switching grades in the winter, spring, and fall. I can drive the cost per mile down around 10%. This is my theory, and haven't done the real math yet. However, I am pretty sure it works. You can even flip the script a tank to match trends.

Like if there is a price spike like a few weeks ago and it is time for 91, just deal with the 87 and then 91.

In the summer I might do two tanks of 91 per 87. Much of that will depend on the temperature. Just popping some math in my head, it can save me between 100 and 200 dollars. I haven't googled it but I am sure it is out there. Or at least proving I have over thought this...

 

[mitdr774]

Over the 17,233 mile tracked and premium averaging about $0.20/gallon more, it is an extra $98 compared to the cost of 87. With the drop in average I was seeing with 87 compared to 93 I would have used an additional 32.63 gallons. The extra fuel would have been $114.86 (average cost per gallon of premium minus $0.20 assumed average rate for 87) or about $17 in extra fuel cost.

In short, running premium only has resulted in paying more per gallon but saving money in the long run.

My numbers may be off a little bit, but I dont think I am off all that much.

 

[GeneralZod]

Over the 17,233 mile tracked and premium averaging about $0.20/gallon more, it is an extra $98 compared to the cost of 87. With the drop in average I was seeing with 87 compared to 93 I would have used an additional 32.63 gallons. The extra fuel would have been $114.86 (average cost per gallon of premium minus $0.20 assumed average rate for 87) or about $17 in extra fuel cost.

In short, running premium only has resulted in paying more per gallon but saving money in the long run.

My numbers may be off a little bit, but I dont think I am off all that much.

Not sure if I explained fully. I know for a fact that 91 is better in every way. However, I don't think our programming effectively uses high grade fuels. Mostly to protect the engine. In the constraints of the stock programming, 89 octane is what might be effective.

In my parts 91-93 octane is 35-45 cents more expensive. With 89 being only 10 cents cheaper.

With the miles I drive I tend to fill up with 2 to 3 gallons left. So there is always residual leftover. When I alternate I generally stay around the same mpg. If I do a few tanks of 91 in a row the bumps is very small. Maybe .5 mpg. If I use straight 87 for two tanks, it is an easy 2-2.5 mpg.

I think that is why the tune is so effective with 91, it is used more effectively. And people that don't beat on the go pedal are nailing over 40 mpg. So with the stock tune I can keep my cost per gallon between 9-10 cents depending on the price. It would be more like 10-11 with straight 91. That 35-40 cent gap gets cut and lowers the cost.

If I had access to 91 at 20 cents over regular, I would buy it every time.

 

[RichieRocket]

I looked into the price difference in my area. I went on gasbuddy.com and looked at a dozen gas stations. The price difference was only 20 cents for a couple stations, but several were 38 to 43 cents!

Wow, I was shocked, I have to shop around more! Most stations only show the price for regular and diesel on the big sign out front...

I have also been doing my own little 87 versus 93 test. I did four tanks of 93 then the last three were 87

93___1323 miles____37.67 gal__35.1 mpg___32.7 mph avg spd
87___1088 miles____31.62 gal__34.4 mpg___30.7 mph avg spd

It sucks that my average speed was lower in the last three tanks. Get caught in traffic a few times and it screws the whole thing up! It's too hard to do a consistent, accurate test for these small changes...

This little bit of squishy data shows <1mpg gain for my commute, my driving habits, etc.

I just pulled the snow tires off and temps are warming up...there are too many variables to so I can't continue the test...

 

[GeneralZod]

The places around me, I get both grades cheaper at Costco. I also use the Costco Amex, which gives money back for use at Costco.

The use of premium has intangible things like response and smoother operation. In the summer I think it can have a long lasting benefit. Think about all the bad things happening with 87 in 90+ degree heat...

 

[Isambard]

In general, when do stations stop stocking winter blend gasoline? I'm in southeast PA.

I want to run a few tanks of 93, but the consensus seems to be that winter blend 93 is not much better than 87.

Edit: Google is my friend

http://auto.howstuffworks.com/fuel-efficiency/fuel-consumption/summer-fuel1.htm

Looks like June 1 through September 15 is guaranteed summer blend.

 

[Swordsmith]

So I hate to buck a trend, but I've been running 87 recently and haven't seen much if any difference between it and 93, either in terms of MPG or power.

Of course, to be fair, I'm comparing both to E85, which is far crappier mpg and far more power, so 93 and 87 both feel anemic, and the mpg on both seems stellar.

If I want to blow money on performance I'll get E85, if I'm driving long distances and won't be having any opportunities for fun, it might as well be 87

 

[GeneralZod]

So I hate to buck a trend, but I've been running 87 recently and haven't seen much if any difference between it and 93, either in terms of MPG or power.

Of course, to be fair, I'm comparing both to E85, which is far crappier mpg and far more power, so 93 and 87 both feel anemic, and the mpg on both seems stellar.

If I want to blow money on performance I'll get E85, if I'm driving long distances and won't be having any opportunities for fun, it might as well be 87

Funny you mention that. Even with the small amount of data in the MPG comp. I can already see a difference in the results for 87 and 91. Don't think the 91 helps on the highway, it is during mix driving that requires acceleration.

When I use 87 I see a drop. In my 80 mile round trip commute 25% of that is in town driving. I see a 2 to 2.5 MPG increase or about a 6%.

When I was hypermiling my Jetta to the Parkway (same commute), guess what. I saw almost the same results.

To prove this we would need a person who drives in the city to try. However, it makes sense that 91 may save gas. You need the power for acceleration, not so much for maintaining highway speeds.

 

[Macehammer]

The competition isn't scientific.

It's not proof of anything.

Short of an automatic reporting system, directly from the car, all records can be forged, miscalculated, etc.

 

[GeneralZod]

While it may seem anecdotal and more qualitative than quantitative, there is something to be gained. Many scientific trials and experiments deal with these issues. That is why a coefficient is built into many studies.

Plus, it is also fun and you too are involved. Yet, you dislike it and don't believe in it.

 

[Macehammer]

Zod,

It's not that I don't believe in it.

I just don't want some type of "miracle-reported" mileage number to grow to be expected in our cars.

I would rather concentrate on the fun-to-drive, modifications, and even safety features of our cars. There is a lot to do and a lot to enjoy in our cars.

Our cars don't have the equipment nor the aerodynamics to be miracle-making mpg machines. If we start advertising 45mpg, and then a lot of folks flock to our model, they might realize what a lot of RS drivers realized post-purchase.

While the Mannies were happy to get the $1K kickback because of false mpg stickers, some may have not purchased the RS, or the Sonic in any variety, had the sticker been truthful. And I don't wanna be part if a group saying "the sticker is lying" to folks interested in buying our car. They might get p*ssed off. It might hurt the model. It might hurt the forum.

So far, I think this forum is a great place for information about just about everything to do with our cars. I was very happy when I stumbled into it and found a great community of people with my car, and with all of this information.

Turning it into a competition... I am not sure there are an equal or greater amount of positives in the cards....

 

[GeneralZod]

Again, the whole thing is for fun. Again, no one said it was concrete. Again, it is done to be a part of the community to create involvement.

You should also then be bashing people doing the 1/4 mile. Some see it as unsafe and wasteful. The car was built for economy, not as a race car or muscle car. People will buy them to street race.

So being built for economy, a MPG competition or comparison is more aligned with he purpose of the car. The car is sporty to create desire in the design. We have gone over this before. This cycle of trying to determine what this is, is nothing more than what it is.

 

[Macehammer]

My initial comment was directed to the notion that:

You get better mileage city driving than highway.

The comment was made using the "competition" as proof.

I was not seeking to reiterate anything either one of us has stated before, but simply to refute someone who, after a week of having the competition, is already trying to use it to make claims that scientifically cannot be backed up given the amount of data gathered, and the way it was provided.

You already knew my opinion, we had already been over it. You wanted to drag this out again. I did not.

The competition doesn't prove anything, except for the fact that I was right about someone trying to use its reported data to make claims that are fallible at best.

Look, I'm not being hostile here.

 

[GeneralZod]

My initial comment was directed to the notion that:

You get better mileage city driving than highway.

The comment was made using the "competition" as proof.

I was not seeking to reiterate anything either one of us has stated before, but simply to refute someone who, after a week of having the competition, is already trying to use it to make claims that scientifically cannot be backed up given the amount of data gathered, and the way it was provided.

You already knew my opinion, we had already been over it. You wanted to drag this out again. I did not.

The competition doesn't prove anything, except for the fact that I was right about someone trying to use its reported data to make claims that are fallible at best.

Look, I'm not being hostile here.

Let us get a couple of things straight, I am not dragging this out and do not deflect it as such. You have had a problem with the MPG Competition while it was being hashed out. Then you enter it, which I am glad you are taking the time to do.

Also, please do not attempt to spin my words in a post. I am not hinging anything on just a weeks of data. I am just noting something I have observed in two different cars over five years of the same commute and requested someone try to see if they see the same results. That is a hypothesis Ian proposing, which in return would require more observational data.

Not sure what your background is in, but I work in and for science and engineering. It all starts with a question, how? Not why, because why is biased.

So when will you start posting that 1/4 time sheets will cause people to think our cars are falsely fast and create illegal street racing?

 

[Macehammer]

You seem to be reiterating everything you stood by in our previous conversation we had about this.

I do have a problem with the competition. My problem isn't with just doing something for SnG. That's fine. That is cool of that is all it is.

I didn't enter anything. I posted one entry with my stats so that other RS drivers could see the mpg I got driving my car because there is an entire thread if RS drivers, and a lot of them are struggling to achieve 33mpg... Trust me, I don't care about who wins your competition. I also don't care about who wins Sonic of the Month, but at least the ppl who win that have photos, and something being 'shopped can be detected. Aesthetics are aesthetics, and beauty is in the eye of the beholder and all of that sh*t, but their "thing" is at least grounded in some type of measurable reality. So don't try to paint me as a hypocrite: my reasons are my own, and my motivations are not fully in line with your own.

I'm not trying to spin anything. You haven't collected any valid data. Your benchmark is honesty. While most folks, even you Zod, that I have interacted with on this forum pass my honest test at the moment; my or your subjective analysis of other people honesty shouldn't be relied upon.

I am not interested whatsoever what you do. You could be Einstein: you could be a janitor. It makes no difference.

Saying, "hey I'm an Engineer, and I know about this stuff." is called "Appeal to Authority." You may know if it. If not, GTS.

The question "why?" isn't biased. The answer to "Why?" always is biased.

I don't have a problem with taking their car to a track and clocking their time, nor do I have a problem with them going to a track and racing. Illegal racing is illegal. It is very irresponsible; you are right. If people want to find a safe place to test what their mods have done, have at it.

 

[GeneralZod]

I was not trying to impose any authority. If I were would I really crown myself with the award you gave me?

Anyway, we have polluted enough threads and eyes. If you want to continue, PM me.

 

[bandita52]

all of my fill ups have been with 87 octane and now i was thinking of putting in a slightly higher octane like 91 or 93. would it be safe for me to do that. is there better performance as far as it cleaning the engines fuel system and different mpg rating.