Regular or Premium fuel? [merged]

[Eclipse_98_RS]

Hi guys, my car is an all-stock RS, but I'm going to start doing some mods to it. Right now I just use regular unleaded gas, but when should I start going up in the octane? After intake/exhaust, or beyond that? I don't want to screw up my engine but I don't want to have to shell out more cash on fuel than I do now. I know, I'm a cheap bastage.

 

[PieEyedPiper]

No, there isn't.

He argues oil, not fuel. Why do you think race gas is high octane?

He doesnt argue oil at all, he closes threads that ask about it and claims oil doesnt make a difference.

 

[fostytou]

ORRRRRRRRRRR.....

You could get DSMLink and get everything remapped for 89 octane:laugh: . Then still piss off your engine when you hit full boost

 

[Defiant]

He doesnt argue oil at all, he closes threads that ask about it and claims oil doesnt make a difference.

I point out from the dozens of oil discussions that are still open that it apparently doesn't make a difference. Getting this idea through to people raised on myth, hearsay, advertising bullshit and con jobs can be daunting. I'm still looking for that motor that Pennzoil "ruined" because it's so "bad".

Actually, I'm wondering why I left another gas thread open. I guess I never realized that like everything else, it'd go up in flames

 

[SpoolnTsi]

Honestly, its should tell you "PREMIUM FUEL ONLY" on the gauge cluster

OK, I just got a 1998 eclipse gs-t. Now the previous owner took exceptionally good care it. He told me that I could burn either Premium, Mid, or Regular in it and that if I use premium I will have a noticable difference in performance.

Is this true, that it will perform better on Premium?

Yes, with heavy throttle conditions. Cruising conditions you wouldnt notice a difference.

If so, which gas will prolong the life of the engine?

The highest grade you can get. Its cleaner

 

[PaintMunky468]

Ok thanks for your help guys. And the reason i dont have an owners mannual is because i got the car 2 days ago, and its not even registered. I plan on getting one soon

 

[erk2581]

just wondering if running premium fuel in dsms is ABSOLUTLEY neccessary

 

[Max-Eclipse]

just wondering if running premium fuel in dsms is ABSOLUTLEY neccessary

No.

It will run on regular... you just might not like the way it runs.

Use premium fuel... yes, it is needed!

 

[tstkl]

there are millions of threads about this, search for them for in depth answers...

a higher octane will always make your car run/last longer, and with turbocharged cars this is twice as true (except if your gettting like 120 octane leaded fuel, leaded fuel is not better) a higher octane fuel is less likely to denote, (knock) which means less wear will be on the engine when the days over....dsms like only the finest, bi*** call her your high-ness

 

[Pitman99505]

Ever since hurricane Katrina hit there must have been 100 threads started about this same subject. A quick search would have provided plenty of answers. Here is one of the latest I think the point gets across well. http://www.dsmtuner.com/forums/showthread.php?t=197006&highlight=premium+gas. I just hope this thread does not go too far. Anyways just go ahead and put in premium, it is not that much more expensive and you won't have to worry about how the car will run.

 

[DGajre777]

The DSM owner's manual does states that IF premium fuel is not available, you can use 87 octane, but there will be a performance loss.

 

[94Jettameowpsst]

I actually ran 16psi on my evo3 on 89 w/ no ill effects. I wouldnt reccomend it cause the only reason i put cheap gas in my car is cause i was going on a trip and there's no sense in putting 900 octane gas in my car if im not gonna be boosting. But as soon as i got back i filled it back up w/ 94.
If you DO plan to run boost, you may have a hard time doin it if your runnin cheap gas. Make sure you have a logger, thats all i gotta say

 

[Defiant]

How strange that no one's ever asked this before.

 

[l3igl3ang]

im just wondering if u can go fauther on premium gas then unleaded gas cause my gst seems to go fauther then my Esi and i heard u can get better gas mileage with premium then unleaded.

 

[knighteclipse1]

I can't correctly answer that question except to say that personally I would think the turbo would suck more gas. I get about 25-28.5 mpg with my eclipse. which I always thought was pretty good considering what a lead foot I have. Of course all turbo cars HAVE to have premium. May consider contacting mitsubishi and seeing what the original cafe standards were for that model year car of yours. Although I never have thought it was worth the trouble to find out myself. If you do, let me know, thats a very interesting question.

 

[HighPsi92GST]

im just wondering if u can go fauther on premium gas then unleaded gas cause my gst seems to go fauther then my Esi and i heard u can get better gas mileage with premium then unleaded.

All gas is unleaded

 

[xveganxcowboyx]

If you use lower than recomended octane your gas mileage will drop some. Going higher than necessary will not likely increase your mileage.

If you're getting better mileage out of your turbo model it probably has to do with other factors.

 

[higaran]

Just a quick thought I had while driving home today: what exactly would be the conequence of running regular grade (87 octane) fuel in my 1G turbo AWD instead of 92 octane?

Consider this:

- I live in a rural area (not much stop-and-go traffic)
- The terrain I drive in is almost completely flat (no hills)
- I am running the engine almost completely stock
- I am not an aggressive driver; I drive for fuel economy.
- it is entirely possible to drive my car to work and back (about an hour) without my turbo boost gauge entering the boost zone even once.

Really, what's the worst that could happen? Even if I drove the car hard (say to pass someone on a two-lane highway in a tight pinch), what parts of the car would be damaged? Would predetonation theoretically damage my valves? Or would it damage my turbo? If it's just the turbo, it might be cheaper to rebuild the turbo every year-or-so than to shell out an extra 15% per year for fuel. I guess it's six of one and half-a-dozen of the other.

Does anyone have experience with this?

 

[Quasimondo]

If you never ever ever ever ever ever ever ever ever ever ever boost your engine, you can run 87 octane and have no problems.

But if you start boosting, you'll ping like crazy, your ecu will eventually revert to a low-octane fuel and timing map which dumps more fuel and takes away more timing and your performance will suffer. That's a best case scenario. Over time, the pinging can damage your bearings and cause piston and other internal damage. FWIW, I've driven on 87 octane unintentionally, and I was reading a full 43 count at 15 psi by the time I hit 3500 on the tach (it was probably more, but the knock sensor pegs out at 43 counts). This was on my 16G and I've also had similar results when I had a 14B.

http://www.streetrodstuff.com/Articles/Engine/Detonation/

Good article to read up on the affects of detonation and preignition.

 

[alex]

Well with that low of octane, you are going to get predetination. The spark will occur too early or too late because of the low octane. The spark is caused by the compression, combustion, and a couple of other things, and when you put 87 or 89 percent octane in there, you will get predetination. With a turbo car, you want atleast 90 octane. If you look on the cluster guage, it even says premium only. I beleive that is how "predetination" works, if not, someone please help me out.

 

[alex]

I was afraid I was going to get beat......

 

[oztofrdm]

- I am not an aggressive driver; I drive for fuel economy.

When i say this i am in No way trying to talk sh*t. But you might want to buy a Honda or some sort of NA application if you are really worried about a few cents extra on the gallon at the pump. That or you should buy a logger and TUNE it for the lower octane but whats the point...

 

[higaran]

OK, what if I turn down my boost so that it barely does anything? I'm not at all familiar with the process, but I understand that it's possible.

Really, if I had a chance to ditch the turbo and drive without it, I probably would. I'm not in this for performance. I'm driving the car because it's Canada, it's wintertime, and an AWD car with ABS and four studded snow tires is really much safer to drive on ice than a Ford Explorer.

 

[toofasteclipse]

Correct me if I am wrong, but isnt the reason we drive DSM's is for the performance? Look at it this way, its your car. Your car gets you to work and back. Would you expect your car to give you less than the best? Then why give your car less than the best. I spend waaaaaay more money on my car than my girlfriend. (I hope she doesnt read this)

 

[kronus]

Well with that low of octane, you are going to get predetination. The spark will occur too early or too late because of the low octane. The spark is caused by the compression, combustion, and a couple of other things, and when you put 87 or 89 percent octane in there, you will get predetination. With a turbo car, you want atleast 90 octane. If you look on the cluster guage, it even says premium only. I beleive that is how "predetination" works, if not, someone please help me out.

Well, this isn't quite exactly how it works. Here, I'll take it right from the source.

Detonation
Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

Pre-ignition
Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.

Hope that cleared up the misconception.
-Kevin-

 

[alex]

I spend waaaaaay more money on my car than my girlfriend. (I hope she doesnt read this)

MINE EITHER.

Being that it does have a turbo and you do want to treat your car right whether you want if for daily driver or performance, you really should use premium gas.