TheSamba.com :: View topic - 87 octane -vs- 93 octane

Sun Oct 18, 2009 9:32 pm

I was hung over last Monday morning and needed to fill Vangina up on my way to work. I mistakenly grabbed the Super unleaded handle rather than the regular and didn't realize it until I was nearly full. I left a little mad that I paid a bit more, but in all reality I'm sure I could come up with the difference in loose change inside my van.

I'm sure that there will be naysayers, but I think that my van is actually running better. I feel that the acceleration is a bit more brisk, and that my exhaust note is a little raspier. Mileage has not been too different either. Is there something to this or is this wishful thinking?

PS correct idle set, fuel to air ratio within spec, injectors in good shape, and a brand new fuel filter.

Sun Oct 18, 2009 9:44 pm

Why don't you have your wife randomly fuel your van for you the next several times and not tell you what fuel she puts in each time , but record it somewhere out of sight. Then once each tankful is nearly gone you can write down your thoughts on how the engine is running. After 5 to 10 tankfuls you can compare your notes with her records and see what has worked and what has not.

Sun Oct 18, 2009 10:25 pm

I too have done that and like the 93 better, I have been told and read you cant notice a difference but I do :D

Sun Oct 18, 2009 11:26 pm

Quote: I'm sure I could come up with the difference in loose change inside my van.

damn you must have alot of holes in your pockets !! premium is quite a bit more cash I think.

Sun Oct 18, 2009 11:35 pm

Crankey wrote: Quote: I'm sure I could come up with the difference in loose change inside my van.

damn you must have alot of holes in your pockets !! premium is quite a bit more cash I think.

about 10-15 cents more so about $2 a tank more so not too bad :twisted:

Mon Oct 19, 2009 5:37 am

Lucky that around this area u can still buy reg without the ethanol added, thats what i use and automatic 2+ mpg on all vehicles. Otherwise when i travel i get what is cheapest,all seem the same.

Mon Oct 19, 2009 7:11 am

I found the opposite. I used Premium when I bought the van and found that it "hunted" at idle so lowered through Super now to Standard and find it optimal.

For me the "hunting" was evidence that the mix was too rich. I'm more of a carb guy, but in the Vanagons, the system is supposed to compensate I guess - but Premium in a CA van in CO seemed beyond it's range.

K

Mon Oct 19, 2009 7:55 am

Wildthings wrote: Why don't you have your wife randomly fuel your van for you the next several times and not tell you what fuel she puts in each time , but record it somewhere out of sight. Then once each tankful is nearly gone you can write down your thoughts on how the engine is running. After 5 to 10 tankfuls you can compare your notes with her records and see what has worked and what has not.

While it may be next to impossible to tell the difference between 87 and 93, I have a feeling that if you paid close attention (listened to idle, throttle response, MPG, etc) you might know if she filled it up with diesel.

Mon Oct 19, 2009 7:23 pm

McVanagon wrote: Wildthings wrote: Why don't you have your wife randomly fuel your van for you the next several times and not tell you what fuel she puts in each time , but record it somewhere out of sight. Then once each tankful is nearly gone you can write down your thoughts on how the engine is running. After 5 to 10 tankfuls you can compare your notes with her records and see what has worked and what has not.

While it may be next to impossible to tell the difference between 87 and 93, I have a feeling that if you paid close attention (listened to idle, throttle response, MPG, etc) you might know if she filled it up with diesel.

Guaranteed it will knock and knock hard if you but enough diesel in it, assuming you can get it started that is. A DS where I once worked filled all the gas rigs with Diesel and all the Diesel rigs with gas one day. Talk about a mess, luckily he never tried to start any of the Diesel rigs after doing so.

Mon Oct 19, 2009 11:46 pm

I wasn't that hung over to use diesel. Plus my wife hates driving it.

Tue Oct 20, 2009 5:26 am

The 93 basically provides benefits to the engine with lots of carbon build-up in the combustion chamber which can and does cause pre-ignition.

Pre-ignition is more noticable on hot days with engine under load.

Tue Oct 20, 2009 8:45 am

Wildthings wrote: Why don't you have your wife randomly fuel your van for you the next several times and not tell you what fuel she puts in each time , but record it somewhere out of sight. Then once each tankful is nearly gone you can write down your thoughts on how the engine is running. After 5 to 10 tankfuls you can compare your notes with her records and see what has worked and what has not.

Wow. Is this a male only forum? I can't imagine women sitting back and taking that! It's the kind of thing I only say when no women are around!

K

Tue Oct 20, 2009 9:28 am

thewump wrote:
Wow. Is this a male only forum? I can't imagine women sitting back and taking that! It's the kind of thing I only say when no women are around!

K

I totally don't get what you're aiming at here. He was offering specific advice to a specific Sambanista who, from his avatar, appears to be a male. His advice is to have a trusted other person do the fueling to allow a blind test of fuel grade. Perhaps it was presumptuous of the poster to assume that a Sambanista would have a trustworthy wife to engage in this endeavor, but in my experience meeting VW people, it's a really solid presumption. I'm as good a feminist as I can be, so what did you find offensive?

Thu Sep 13, 2012 6:14 pm

I have made two trips to the USA from Mexico and have found that the Van runs better with the 87 in Mexico than the regular in the USA. When up north I use at least 91 octane and get good results. I assume this is the result of the non polluting agents, I guess our gas down here is of the 1985 vintage that my Westy likes.
Also I sealed the tank with some gunk I got here and it worked OK in Mexico, but on my trip to the USA the gasoline ate this stuff and plugged my filter numerous times making my trip horrible. I have just put on the reseal kit from Van Cafe and so far it looks good, the test will be on my trip north next May 2013, plan to go up to Montana. Cannot wait!
All the best

Thu Sep 13, 2012 11:00 pm

Always use the highest octane value available. :wink:

Fri Sep 28, 2012 4:55 pm

wenholzm wrote: I assume this is the result of the non polluting agents, I guess our gas down here is of the 1985 vintage that my Westy likes.
All the best

I've been looking in to gas related discussions,
mainly because my van is going from "daily driver" duty
to "recreational" ... less than a tank a month.

i've been reading a lot about ETHANOL added to
our fuel here in the states, which many report a 10%
decrease in fuel efficiency.

since i'm going to be going through less gas nowadays,
i'm looking at putting ONLY ethanol-free gas in my van:
http://pure-gas.org/

Fri Sep 28, 2012 6:22 pm

Pure gas is the way to go if you can find it close to you. I have noticed a ~1.5 mpg difference in city driving and more on the highway. The closest station is about a gallon of gas round trip distance away so it isn't worth getting for me. But if I wasn't needing mine everyday that would be the only fuel I would use.

Fri Sep 28, 2012 6:55 pm

The higher octane fuels don't burn more fully, or more faster, or provide more power so you would not notice any difference at all. Was once part of a study evaluating people's ability to discern the difference in powertrain outputs, etc - people could not really detect even sizable differences.

DougM

Fri Sep 28, 2012 8:08 pm

Owning several older carbureted rigs, I have been forced to switch to ethanol free over the last year. They just will not hot start on regular with any ease anymore. My bus engine will 9 times out of 10 fire on the first cylinder that ticks over on ethanol free high test, but will take 15 or more seconds of cranking at WOT to hot start on regular. My wife forgot to fill my Thing with high test last time and she has twice had to just sit and wait an hour for the engine to cool so that she can get a restart. My seldom used Dodge which had 8-9 year old fuel in the tanks started last year and ran will little effort, but after running a couple of tanks of regular through it and then letting it sit for a month the fuel gelled in the carb.

I used to revel in running low octane fuels like Gulftane and Sunoco 170 in bygone days while friends felt they needed to run the higher grades in similar models, but today I have been forced to move to high test on my carbureted rigs. As for FI rigs I can't say yes or no at this point.

Fri Sep 28, 2012 10:05 pm

Yeah, the ethanol regular gasoline is a total clusterf#ck from the word go. You probably already know what happened, but the ethanol can strip settled stuff from normal gasoline accumulated over the years and make it mobile (liquid) all at once. Likely the Dodge's situation. I have absolutely nothing good to say about these E10/15 fuels. They are a total waste of taxpayer money and they are damaging the things we use them in. The program is now considered an agricultural subsidy and will never go away as a result. I'd much rather simply cut farmers a check, personally.

You can find a station in your area selling "real" gasoline by googling for the website that has these locations by zip code. Can't recall it. We have one, fortunately.