About 2 weeks ago, I had to fill up but was broke, so I had to fillup on the cheap stuff which was 87 octane. Typically I use supreme (here is 92 octane) and was hesitant but I did so anyways. I was under 1/4 tank and filled up with the 87 octane. It's been HOT around here .. 70-85 degrees ...

After about 20 miles or so, I noticed my car was laggy or bogging down kinda. At an idle, it sounded okay .. but when I would give it some gas, the SRI makes sounds as if it were farting louder than before. Generally, the responsiveness lags compared to BEFORE i filled that tank of gas. I went ahead and checked my liquids, SRI and other things ... and the loudness/laggyness of the engine continued.

I then wondered if It was becuase of my 87 octane gas. So, I ran my AC as much as possible .. trying to burn up the gas .. and I finally got to re-fill today. I refilled with 92 octane .. and after about 5 miles or so, I noticed that the laggyness of the engine has gone away. THe heat hasn't changed .. the only thing has been the gas.

Has anyone else had this issue? Is it possible to get a "bad" tank of gas?

Any thoughts are appreciated!

I'd be extremely suprised if you were detonating without forced induction or raise compression.

Hmm why fill up when you are below a quarter tank with gas that you know is only for "emergencies"? (Use a credit card next time)

Also, 80 degrees is hot???? On what planet?

This is the reason I bought my Evo new and will always buy performance cars new. You never know what someone did "just this one time"....

[I just noticed it's a regular Lancer, not an Evo - OOPS ]

I've got no boggy feelings with my car, and I've got a short ram and fill up on 87 octane regularly.

I can't imagine octane having any effect on a naturally aspirated lancer like that. I run 87 all the time (seriously no need for anything higher) and have an SRI. Mine seems to bog a little no matter what fuel I use (I've used 87 and 91), but only a little in the lower RPM range, and that was partially taken care of by adding a scoop and ducting to feed more air in the general direction of the air filter (see my registry for pics) Hope that helps some.

Oh yeah, and I live in California, and the SRI is doing fine at 100+ degrees day in, day out.

Update on this. And I learned me a lesson.

Seems that the bolts on my test pipe were loosening .. due to that, it blew part of the gasket out. I had an exhaust leak because of this and the engine was really 'boggy' in first gear. I also noticed a farting sound from the TP when downshifting. I think the lack of back pressure had some sort of issue with the O2 sensor and it not reading right? Either way .. I replaced the gasket and tightened the bolts back down, using lock-tite this time and all is good.

My lesson = do the job right the first time .. and check on it after a few miles to ensure your bolts are tight. :P Thanks for the input guys.

I just hope you're not running that high octane gas still. Remember, the higher octane, the less readily combustible as lower octanes, effectively robbing this low output engine of that oh so vital power. That's why highly tuned cars run it to avoid detonation because of high boost pressures, some majorly advanced timing or high compression ratios. Urban's quite right in saying there's no need to run anything higher. As for my own shortie v. hot weather tales, my HKS filter sits almost quite literally on top of the in-bay fuse box, well enough away from the oh so hot exhaust manifold. Any car on a hot day will bog, just how it goes since the air is less dense.

You've got to stagger your intake-exhaust mods or you'll bogg either low end or high end. A test pipe is a good mod, but a cat back exhaust would've been a better choice to compensate for the SRI. You'll have a little boggier low end until you do so.

So pjal84 - your saying that a stock lancer (a non-turbo or lightly modded) should see no performance gains (or very little) with a 92 octane versus an 87 octane? Kinda seems pointless to run "good" gas in our stock/lightly-modded stock lancers then.

Thinking about this .. RRM's ECU is desinged for 87 octane on NA lancer engines .. thats probably what Im gonna start running too.

I've actually found that (after replacing my plugs) the higher octane (92) makes the engine run smoother, more responsive with AC on and I get better gas mileage. Hmmm ...

Need the catback I do .. :P Thanks for the thoughts guys!

Actually RRM's ECU is designed for premium unleaded(91+ octane). Basically reiterrating what pjal84 said about "advanced timing".

the octane itself shouldn't give you any changes in gas mileage.. its the mods to the car that help with that

Actually, last I checked, RRMs new ECU was set up for 91 octane or above. We've got 93 in Illinois so that's fine by me.

You really won't see enough of a difference to warrant the extra 2 bucks a fillup costs with 91 (or up). I used 93 for the first 6 months, and after that, only 87.

Maybe in winter (like here, where it gets to -15 all the time) you might want to use a higher octane. Winter gas is not nearly as good at keeping things smooth as summer gas.

Winter gas usually has additives to prevent low-volume freezing. There might be more filler in there too.

Here is some info on this guys and other articles on this same question can be found all over. Overall you are going to get this same response tho. With no type of upgrade except for basic bolt ons there is no need to run a higher octane than teh manufacturer recommends
http://www.accesscom.com/~knliao/octane.html

70-85 degrees is hot? I'd love to feel that heat. It's so hot and muggy outside now (90+) it's hard to even breathe. It does rain daily however which is probably about the same as throwing water on the coals in a sauna.

Also, you are driving a Lancer which is in itself - laggy and boggy. Seriously though I don't think the gas made the difference. My car seems to sometimes run top notch and other times couldn't get out of it's own way - all on the same tank of gas. I run 89 consistently. However, I don't buy gas from off-the-wall stations and convience stores. Usually use Mobil or Shell.

Exactly, Use big name gas stations, not TOM's fill-up,the tanks are cleaned regularly and you know what your getting. As for octane I tryed every thing from 87 to 94(NY)with octane booster, no difference, now mostly 87and sometimes 89 (its all in your head because you payed more!