Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Boxster General Discussions

Reply
 
LinkBack Thread Tools Display Modes
Old 04-28-2008, 07:13 PM   #1
Registered User
 
Join Date: Oct 2007
Location: Vero Beach
Posts: 142
Send a message via AIM to PSL-Boxster
Unleaded Plus vs. Unleaded Premium

is there really a difference if i use unleaded plus gas instead of the suggested unleaded premium? my sister does it in her car (which isnt a porsche but also is suggested to run on premium) and has no noticeable difference in hp or gas mileage - is it ok for porsche engines to run on this type of gas for the sake of saving a couple bucks every time i fill up?

PSL-Boxster is offline   Reply With Quote
Old 04-28-2008, 07:33 PM   #2
Registered User
 
Join Date: Feb 2008
Location: Miami
Posts: 28
Send a message via Yahoo to 6speed
I would think the porsche would run on it. It has what porsche calls a Knock sensore. But you failed to mension exactly what car she has. You know porsches are fine tuned and i would think it would make a diffrence.
__________________
NUFF SAID......
6speed is offline   Reply With Quote
Old 04-28-2008, 09:24 PM   #3
Registered User
 
Join Date: Jan 2005
Location: Dallas, TX
Posts: 1,460
Yes it will run on less. I wouldn't do it -but that's just me. Mine's not a daily driver. Boxsters have been known to throw check engine lights if less than optimum gas is used. So I don't put anything less than 93 octane in mine.

My cousin has an '08 Jetta that recommends premium. He only fills that up with premium about every 4th tank. Says it's doing fine. (Got it in January new and has already racked up 14,000 miles on it!)
__________________
.
1997 Honda Accord | V6
2004 BMW 330i | ZHP | SOLD
2000 Porsche Boxster | SOLD | http://www.986forum.com/forums/showthread.php?t=9114

http://www.kryzak.com/storage/986sig12.jpg

http://kryzak.tumblr.com
Jeph is offline   Reply With Quote
Old 04-29-2008, 04:58 AM   #4
Registered User
 
Join Date: Apr 2006
Location: Collegeville, PA
Posts: 61
Send a message via AIM to dmenn
Last time I checked you owned a Porsche - suck up the couple bucks and put in the type of gas that it's supposed to take.
__________________
2000 Boxster S, Arctic Silver, Natural Grey Leather
Factory: Aerokit I, 18" Sport Classics, Xenons, Heated Seats, Premium Sound, and more..
Upgrades: Bumper Plugs, Door Plug, Clear Sides, Clear Tails, Clear Bulbs, Painted Bumperettes, 997 Shifter, EVO Intake
dmenn is offline   Reply With Quote
Old 04-29-2008, 05:58 AM   #5
Registered User
 
Join Date: Dec 2006
Location: Tampa, Fl.
Posts: 118
I also owned a BMW E46 323is that I daily drive. Last year I did a test where I filled up 10 tanks with 87 and 10 tanks with 93. I started the test with the tanks completely filled and ended them filled. I then averaged all 10 tanks so the differences in volume should be very minimal.

I know this test was not very scientific since there are variables I didn't account for (like driving style, conditions, weather, etc..) but I tried to keep everything as consistent as possible.

End results: Although I could not feel a difference in performance, I did notice my fuel economy went up 12% while the added cost went up only 8% (this is back when fuel was 3 dollars a gallon) so it was actually less expensive for me to run premium over standard (as fuel prices rise, the savings is even greater.) Couple this with the fact that the car was designed to run on premium (like the Boxster) and my decision became a no brainer.
__________________
http://img260.imageshack.us/img260/5...1067ia8.th.jpg

00' Boxster S, 00' E46 BMW - DD, 03' LR Disco - Wife's car, '84 300ZX turbo - owned for over 22 years, 82' 911 SC - Gone but not forgotten

Last edited by Rob-00BoxsterS; 04-29-2008 at 08:33 AM.
Rob-00BoxsterS is offline   Reply With Quote
Old 04-29-2008, 06:25 AM   #6
bmussatti
Guest
 
Posts: n/a
Let's say:

-You drive 15,000 miles per year
- And you average 22 MPG
-That's about 681 gallons of fuel
- At a $0.12 price premium for the 93 octane (vs. plus)
- You pay an extra $82 for the "right" gas
- That's about equal to 38 cups of Vente Starbucks!
- So, use the right fuel, and cut back on 1 Starbucks per week, and you'll come out ahead.
  Reply With Quote
Old 04-29-2008, 08:09 AM   #7
Registered User
 
Brucelee's Avatar
 
Join Date: Jun 2004
Location: Des Moines, IA
Posts: 8,083
Quote:
Originally Posted by Rob-00BoxsterS
I also owned a BMW E46 323is that I daily drive. Last year I did a test where I filled up 10 tanks with 87 and 10 tanks with 93. I started the test with the tanks completely filled and ended them filled. I then averaged all 10 tanks so the differences in volume should be very minimal.

I know this test was not very scientific since there are variables I didn't account for (like driveling style, conditions, weather, etc..) but I tried to keep everything as consistent as possible.

End results: Although I could not feel a difference in performance, I did notice my fuel economy went up 12% while the added cost went up only 8% (this is back when fuel was 3 dollars a gallon) so it was actually less expensive for me to run premium over standard (as fuel prices rise, the savings is even greater.) Couple this with the fact that the car was designed to run on premium (like the Boxster) and my decision became a no brainer.

That is interesting work and I think it synchs up with the theory on octane and mielage. Thanks for telling us.
__________________
Rich Belloff

Brucelee is offline   Reply With Quote
Old 04-29-2008, 10:30 AM   #8
Registered User
 
Lil bastard's Avatar
 
Join Date: Feb 2008
Location: Du Monde
Posts: 2,199
So far as Calorific, BTU or Joules are concerned, generally speaking, lower octane fuel contains more energy than higher octane fuel.

This is because the additives used to boost octane contain less calories/volume than normal gasoline - they make the fuel more difficult to combust so that it can be better compressed and burn more thoroughly releasing more useful energy. Since these additives displace a % of normal gasoline when mixed for octane purposes, this gallon of octane boosted gas will contain less energy, somewhere on the order of 5-10%. This is also a problem with Ethanol - it contains 30% less energy/volume than regular gasoline.

Now, the issue becomes potential energy.

Some engines, due to better computer control, higher compression, etc. can release more useful energy from octane boosted fuels than normal gasoline, or perform better - create more HP or run more smoothly.

That is not to say they perform badly on regular gasoline, in fact, due to the wide variation in fuel quality around the world, most cars marketed internationally are setup to run just fine on a wide variance in octane. The Boxster is one of these.

Since there is no tetra-ethyl lead in any of these fuels, none of them will hurt the engine or emissions gear.

If mine were a daily driver, I'd use 90 Octane and only go to Super-premium for track or weekend spirited runs.

But, you hardly need to eek out that extra 0.1 sec. 0-60 when commuting.

Now, that said, there is often some variation between what is stated on the pump and the actual octane rating of any particular batch of fuel, in fact, it's usually slightly lower than stated due primarily to the volatility of the octane additives, which evaporate from the fuel as it sits in the Tankers or underground storage tanks. But, if you fill-up at the busiest name brand station you can find, this isn't usually a problem.

Try several grades of fuel, and use the one which gives you the best value for your money. Because of driving style, conditions, source of fuel, etc., there is no one answer to this question - you need to experiment on your own. You won't hurt the car at all. You may run a little rougher, or see reduced range and if so, just switch back. The savings may be small, but in this day of ever-rising fuel costs and uncertain immediate economic future, it pays to save wherever you can.
__________________
1990 Porsche 964 Carrera 4 Cabriolet
1976 BMW 2002
1990 BMW 325is
1999 Porsche Boxster
(gone, but not forgotten)
http://i933.photobucket.com/albums/a...smiley-003.gif

Never drive faster than your Guardian Angel can fly!
Lil bastard is offline   Reply With Quote
Old 04-29-2008, 10:36 AM   #9
Registered User
 
Join Date: Oct 2007
Location: Vero Beach
Posts: 142
Send a message via AIM to PSL-Boxster
thanks guys, i never thought of the octane<>gasmileage feud. i was mainly wondering what long term affects could come other then the occasional check engine light
PSL-Boxster is offline   Reply With Quote
Old 04-29-2008, 10:56 AM   #10
Porscheectomy
 
Join Date: Mar 2006
Location: Seattle Area
Posts: 3,011
Quote:
Originally Posted by Rob-00BoxsterS
I also owned a BMW E46 323is that I daily drive. Last year I did a test where I filled up 10 tanks with 87 and 10 tanks with 93. I started the test with the tanks completely filled and ended them filled. I then averaged all 10 tanks so the differences in volume should be very minimal.

I know this test was not very scientific since there are variables I didn't account for (like driving style, conditions, weather, etc..) but I tried to keep everything as consistent as possible.

End results: Although I could not feel a difference in performance, I did notice my fuel economy went up 12% while the added cost went up only 8% (this is back when fuel was 3 dollars a gallon) so it was actually less expensive for me to run premium over standard (as fuel prices rise, the savings is even greater.) Couple this with the fact that the car was designed to run on premium (like the Boxster) and my decision became a no brainer.
I know you mentioned that your test wasn't scientific. I appreciate your admission. Fuels have different formulations at different times of the year, and economy is heavily effected by the air temperature and humidity as well as the other factors you noted.
blue2000s is offline   Reply With Quote
Old 04-29-2008, 11:32 AM   #11
Porscheectomy
 
Join Date: Mar 2006
Location: Seattle Area
Posts: 3,011
Quote:
Originally Posted by Lil bastard
So far as Calorific, BTU or Joules are concerned, generally speaking, lower octane fuel contains more energy than higher octane fuel.
The key here is "generally speaking" because there are various mixtures used to boost fuel octane and they don't all decrease the energy content of the fuel.
blue2000s is offline   Reply With Quote
Old 04-29-2008, 12:16 PM   #12
Registered User
 
Join Date: Nov 2007
Location: N. California
Posts: 26
Quote:
Originally Posted by Rob-00BoxsterS
Last year I did a test where I filled up 10 tanks with 87 and 10 tanks with 93. I started the test with the tanks completely filled and ended them filled. I then averaged all 10 tanks so the differences in volume should be very minimal.
Did you run 10 tanks of one octane followed by 10 of the other, or did you switch back and forth in some manner?

The extreme of 10 of one then 10 of the other is the least valid because the variation in temperature, season, mechanical factors (tire pressure among others), and gasoline blend would be difficult to control.

At the other end of the spectrum, alternating 20 tanks isn't a great idea because you are blending the two octanes to some extent with each fill (so the actual octane is somewhere in between). Also, I don't know for a fact how long it takes the car to completely adjust to the new octane... is it instantaneous (my assumption), or does it take 5 miles or 50 miles? (Insight on that question is welcome if anyone knows.)

If anyone plans to run this type of test, I might suggest running three tanks one and then three tanks of the other and repeat this for three or four cycles. Make some note of your balance of highway versus stop-and-go driving for each tank, check tire pressure with each fill, and note general patterns of high temperatures (for instance, 50s / 70s / 90s). We could draw some conclusions out of that sort of data.

I won't personally be doing this... I'm in CA with the highest octane of only 91 (aka craptane). I'd be happy to test 91 versus 93 or 94 if that were possible but have no interest in testing 89, which saves only ~12 cents a gallon and is below Porsche's minimum recommendation.
Hops is offline   Reply With Quote
Old 04-29-2008, 01:56 PM   #13
Registered User
 
Join Date: Dec 2006
Location: Tampa, Fl.
Posts: 118
Quote:
Originally Posted by Hops
Did you run 10 tanks of one octane followed by 10 of the other, or did you switch back and forth in some manner?

The extreme of 10 of one then 10 of the other is the least valid because the variation in temperature, season, mechanical factors (tire pressure among others), and gasoline blend would be difficult to control.

At the other end of the spectrum, alternating 20 tanks isn't a great idea because you are blending the two octanes to some extent with each fill (so the actual octane is somewhere in between). Also, I don't know for a fact how long it takes the car to completely adjust to the new octane... is it instantaneous (my assumption), or does it take 5 miles or 50 miles? (Insight on that question is welcome if anyone knows.)
...

I didn't switch back and forth but I did run two tanks of regular (and discarded the results) before starting the test on the regular. The super was what I normally used so no data was dropped.

I realized I was not taking into account many factors but I did try to be as consistent as I could. Tire pressure was checked every weekend (habit I have, not just for the tests). There was a few times I need to drive a substantial distance on the interstate so I took a different car so as not to throw off my results. All traveling was done in town (but even that could be considered inconsistent) and the 20 tanks took me a good 5 to 6 months to complete so temperature would have been a big factor it didn't account for (although it is always hot in Florida .)

Quote:
Originally Posted by blue2000s
I know you mentioned that your test wasn't scientific. I appreciate your admission. Fuels have different formulations at different times of the year, and economy is heavily effected by the air temperature and humidity as well as the other factors you noted.


That is one of the things I really like about this forum. People here are usually so respectful when they post a reply (I mean that sincerely, I'm not being sarcastic. ) You are right and I didn't even think about different formulations or humidity.

My apologies for not being more thorough but when I did this, I was not expecting to pass my finding off as fact. I did it more out of curiosity because my wife was getting such bad fuel economy in her Land Rover and she was too thrifty to put in 93 octane.
__________________
http://img260.imageshack.us/img260/5...1067ia8.th.jpg

00' Boxster S, 00' E46 BMW - DD, 03' LR Disco - Wife's car, '84 300ZX turbo - owned for over 22 years, 82' 911 SC - Gone but not forgotten

Last edited by Rob-00BoxsterS; 04-29-2008 at 05:40 PM.
Rob-00BoxsterS is offline   Reply With Quote
Old 04-29-2008, 02:36 PM   #14
Registered User
 
Join Date: Nov 2007
Location: N. California
Posts: 26
Quote:
Originally Posted by Rob-00BoxsterS
People here are usually so respectful when they post a reply
...

My apologies for not being more thorough but when I did this, I was not expecting to pass my finding off as fact.
I agree with you. I've only seen a few people bicker on here, and I don't understand the point of taking time out of your day to go online and bicker with someone. This is by and large a very friendly forum.

Thanks for providing a little more detail on your method. I am glad you ran your tests. None of the rest of us have gotten off our arses and done it. If I come across as an analyst or something, well, I am. It would be cool to get enough data with enough variables trapped to really get a read on how big of a factor octane rating is in the overall fuel economy of our cars.

Unfortunately the number one factor is our right feet. I've done as high as 28mpg and as low as 16mpg in my '05 987S. As I think about this a little more, the best measure may be mpg over a controlled course using the onboard computer. So, driving multiple runs on a defined section of highway with the cruise set at 65 (or whatever) and resetting the onboard mpg at the beginning of each run might be the best apples to apples comparison... and it wouldn't take months to complete. Of course, this doesn't necessarily reflect the mpg difference in normal driving patterns, but it would be a start.
Hops is offline   Reply With Quote
Old 04-29-2008, 03:39 PM   #15
Registered User
 
Lil bastard's Avatar
 
Join Date: Feb 2008
Location: Du Monde
Posts: 2,199
Quote:
Originally Posted by blue2000s
The key here is "generally speaking" because there are various mixtures used to boost fuel octane and they don't all decrease the energy content of the fuel.
Exactly... There are fuels which contain more energy and higher octane, but these are usually special concoctions costing much more and not generally available at the pump.
__________________
1990 Porsche 964 Carrera 4 Cabriolet
1976 BMW 2002
1990 BMW 325is
1999 Porsche Boxster
(gone, but not forgotten)
http://i933.photobucket.com/albums/a...smiley-003.gif

Never drive faster than your Guardian Angel can fly!
Lil bastard is offline   Reply With Quote
Old 04-30-2008, 01:26 AM   #16
Registered User
 
Join Date: Jun 2007
Location: Bay Area, CA
Posts: 119
the higher octane is primarily to run more timing. lower your timing down, and run all the 87 octane you want. the car can automatically retard timing, but only so much.

but why would you want to retard timing when you own a porsche, to save a couple of dollars/fill-up?

on the flip side, if you run higher octane, like 100, etc. then bump the timing, and get more power : )
__________________
http://b-ng.com/audi/images/avatar.jpg
Benny
lubrify.com
Benny986 is offline   Reply With Quote
Old 04-30-2008, 06:45 AM   #17
Registered User
 
Join Date: Feb 2008
Location: Miami
Posts: 28
Send a message via Yahoo to 6speed
Thats what porsches " knock sensor (TM) " does !
6speed is offline   Reply With Quote
Old 04-30-2008, 07:01 AM   #18
Registered User
 
Brucelee's Avatar
 
Join Date: Jun 2004
Location: Des Moines, IA
Posts: 8,083
Unfortunately the number one factor is our right feet.

Boy, you got that one right!
__________________
Rich Belloff

Brucelee is offline   Reply With Quote
Old 04-30-2008, 05:47 PM   #19
Registered User
 
Join Date: Oct 2007
Location: Vero Beach
Posts: 142
Send a message via AIM to PSL-Boxster
Quote:
Originally Posted by Brucelee
Unfortunately the number one factor is our right feet.

Boy, you got that one right!
double true -- i have the tiptronic option which helps with mileage more then i thought it would initially
PSL-Boxster is offline   Reply With Quote
Old 05-11-2008, 04:51 AM   #20
Registered User
 
Join Date: Dec 2006
Location: Tampa, Fl.
Posts: 118
Sorry to go OT but I found this interesting:

I also own an old Nissan 300ZX turbo and frequent a few Z31 sites. A thread was started almost identical to this one on one of those sites and I pretty much did a cut-n-paste from my above written posts.

Instead of respectfully pointing out the flaws in my data collection or seeing how the data could be beneficial to them (like what was done on this site) they turned it into a pissing match on what octane ratings mean. I was also called stupid for trying to say I know the car better "then the people who made the car from ground up and tested it's flaws. (<= direct quote from that thread.) The data was ignored while the members there competed in a game of "Who has the bigger e-penis."

This forum and the Land Rover forums are the only two I have been on that show respect to their fellow members and talks to them like they would if they were face to face. It's very refreshing.

**Note** This post is not meant to bash on other sites, just to compliment this one. Unfortunately, this site provides no information on my other vehicles no matter how hard I search so I do need to continue to frequent them.

__________________
http://img260.imageshack.us/img260/5...1067ia8.th.jpg

00' Boxster S, 00' E46 BMW - DD, 03' LR Disco - Wife's car, '84 300ZX turbo - owned for over 22 years, 82' 911 SC - Gone but not forgotten
Rob-00BoxsterS is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 02:36 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page