Subaru WRX Forum banner
1 - 20 of 30 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
This is classic...the dealership told me just to fill up with regular. Today (being 3 weeks later) I'm filling up and notice a sticker that says use Premium only. Input on this? Does it honestly matter? :confused:
 

·
Premium Member
Joined
·
6,750 Posts
You've been filling up with regular for 3 weeks? :( What a stupid dealer! :mad:

From what I know, you have to use premium...the higher octane helps prevents detonation in our high-performance engines. Not only is it a performance issue, but it's an engine safety issue as well. Someone with more techinical knowledge will probably chime in here with more details...
 

·
Premium Member
Joined
·
6,750 Posts
Hey, no worries bud...we were all young once :) I'm not even that much older than you anyway. Just make sure you use premium from now on! :)
 

·
Banned
Joined
·
7,636 Posts
becasue most of the car's engine was designed for europe and japan, it was also designed for higher octane fuel. here in the states we're lucky to see 94 (we get sunoco ultra up here in boston)

lower octane fuel will burn less clean, and leave more carbon deposits and gunk build up in your valves. the carbon deposits can be burned off with techron fuel system cleaner (however most of those products are gimmicks with no real results)

run the premium, it'll ensure a longer, higher performance life for your rex.

dR
 

·
Thinking Man's Engine
Joined
·
1,598 Posts
Lower octanes burn faster than higher octanes.

The problem is, with lower octanes, since the burn rate is faster, there's a large chance of detonations (also known as pinging & knocking). THe offset this effect, it has knock sensors, where when detected tells the ECU to retard the timing. This decreases performance and possibly gas mileage.
 

·
Registered
Joined
·
2,155 Posts
Soobasaurus Rex said:
if you still have it in there just let your car sit and idle and burn it all the way down then go fill up on premium....
I think I'd go top it off with higher octane fuel and not waste a lot of gas. I'd probably take it easy and not stomp on it, but I wouldn't really want to "throw" away the tank I had.
 

·
Moderator
Joined
·
1,377 Posts
dark_rex said:
lower octane fuel will burn less clean, and leave more carbon deposits and gunk build up in your valves. the carbon deposits can be burned off with techron fuel system cleaner (however most of those products are gimmicks with no real results)

run the premium, it'll ensure a longer, higher performance life for your rex.

dR

No! it isn't a less clean burning fuel. If you put high octane in a low octane requiring engine it'll create more carbon build up.

The reason you use higher octane is for higher compression engines... although it's a low (8:1) compression, the turbo makes it a high compression engine.

You should always use the lowest possible octane that is rated for your car without causing knock and predetonation, etc
 

·
Moderator
Joined
·
1,377 Posts
Soobasaurus Rex said:
if you still have it in there just let your car sit and idle and burn it all the way down then go fill up on premium....

You don't want your car idling for any longer than needed (like stop and go traffic). It helps build carbon deposits if you let the car idle. Just add higher octane fuel to the existing tank and wait until all the low grade is out.
 

·
Registered
Joined
·
3,501 Posts
Leaving a 2.0L engine idle with 13 gallons of fuel to burn is the stupidest idea I've heard in a long time. By my calculations it would take well over two days to consume all of the fuel in the tank. In the mean time, the oil would get very hot and the bearings would wear excessively in their "idle tracks."

Just use the fuel. The ECU will adjust. Living in NJ, I get the occassional dim wit gas station attendent that fill my tank with regular. It causes no harm, just limits the engines ignition advance, which limits power. Dump some octane boost in the tank if you are realyl worried about it.

dark_rex, what do you think of B12 chemtool. That stuff kicks fuel system deposit ass, IMO.

-Jim
 

·
Banned
Joined
·
7,636 Posts
okay, let's cover a few things here.

if you still have it in there just let your car sit and idle and burn it all the way down then go fill up on premium....
thank you plat. that is rediculous, and also really bad for the car in a number of ways.



No! it isn't a less clean burning fuel.
i'm sorry, but higher octane fuel carries more combustive material than lower levels. this allows for a hotter and more complete reaction.

If you put high octane in a low octane requiring engine it'll create more carbon build up.
that is true, but like i said, this engine is not designed for low octane ratings. putting lower octane fuel therefore burns less efficiently, leaving more waste in the combustino process.


You should always use the lowest possible octane that is rated for your car without causing knock and predetonation, etc
why? i've never heard that before. i know the wrx in japan and europe run on higher octane levels than the US.

bottome line, buy the top of the line (or premium ) fuel only. says it right on the cap.

i've heard of it jim. i know ROADS corporation out here in MA uses the stuff, becasue they used to special order it from MAWDI. i've only heard good things about it. the TECHRON fuel sytem cleaner is the only stuff that i know of that works so far. the GUNK brand is a total gimmick. is it pricey? got a link? hook it up.

dR
 

·
Registered
Joined
·
339 Posts
Here's an interesting one. Out here in Ill. (I'm traveling for buisness) at the Shell station they have 89 for Econo, 91 for Midgrade and 93 for premium. I've always seen 87, 89, 91 or 93 in the past so is gas going to change? If so that means we could get midgrade and be fine. Has anyone else seen this? Just wondering.
 

·
Registered
Joined
·
18 Posts
I don't think you did any damage with the advanced computers they put in cars today just start running Prem. Entresting side note: Years ago Car and Driver (Back in the David E. Davis days) had a formula for mixing reg and unleaded to achieve a higher octane. Like I said this was years ago but I bet if you do enough digging or bother Don Sherman the old tech editor there you can get it. Other rambling side note: As a teen I was fortunate to own a 1967 Ford Fairlane GTA with the Thunder Bird 390 engine (it used the same cam as the later Mach 1 428 Mustang) any ways the owners manuel warned you not to use anything less than 98 octane. :)
 

·
Registered
Joined
·
14 Posts
hey guys be easy on me... i was just going by what i thought would be logic because i thought it would just get the gas out without having to really use it.... i think i rememeber someone telling me ones that octane is how pure the fuel is... a higher octane is a cleaner fuel... kinda like tap water or bottled water... i apologize and admit my stupidity... but if i own a WRX i only can be so stupid...
 

·
Moderator
Joined
·
895 Posts
what kind of "higher octane" does Europe and Asia get that we don't get? if its something like race gas (104 or so) then i'm movin' overseas :D

i get 93 in houston, so i guess thats pretty good gas. but whats the difference in gas brands? i mean, WTF is that chevron w/ techron junk? anyone know if that crap helps any?
 

·
Thinking Man's Engine
Joined
·
1,598 Posts
Penguinking said:
what kind of "higher octane" does Europe and Asia get that we don't get? if its something like race gas (104 or so) then i'm movin' overseas :D

i get 93 in houston, so i guess thats pretty good gas. but whats the difference in gas brands? i mean, WTF is that chevron w/ techron junk? anyone know if that crap helps any?
I believe stuff like 96 and 98 octane. And how wonder why gas is so expensive over there....
 

·
Banned
Joined
·
7,636 Posts
gas is also more expensive over there becasue they don't have a nice little treaty with a prince in saudi arabia.

different brands use different additives. for example, texaco and sunoco both use detergents.

dR
 
1 - 20 of 30 Posts
Top