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Resolved 1G Cleaned gas tank and accidentally filled with 87 gas, ok to drive for couple of miles?

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
So I just finished overhauling my '92 Talon TSi AWD's entire rear end, including dropping and cleaning out the gas tank and replacing all the hoses. I got a couple of gallons of gas to put in the tank so I could drive it to a gas station to fill it the rest of the way, and there was an attendant there who filled up my containers and I forgot to tell him to put in premium gas, so he put in 87, which I didn't realize till I left.

I know that 87 is bad for these engines, but I put it in the tank anyway, along with several ounces of Techron (didn't have any octane booster, only this and MMO), and the car started up, but the engine felt slightly rough after 10-15 seconds, so I shut it down. But it had been running a bit rough on idle before I dropped the tank so it might be unrelated.

Am I good to drive to the nearest gas station, around 2 miles from here, to fill it up with premium, so long as I don't boost the turbo or go too fast, say 30mph? And do I need to fill it up all the way, or is 5-6 gallons ok? Gas prices are still pretty high here and I'm not going to be doing much driving over the next few weeks, so I'd rather wait and save a few bucks. But I'll do what's best for the car. And should I add some octane booster or something else?

Btw, this was a MASSIVE undertaking and had I known how long it would take and how hard it would be, I'd have broken it up into several projects instead of doing it all at once. I mean I took EVERYTHING out, subframe, diff, carrier, upper, lower & trailing arms, sway bar, CV axles, axles, calipers, tank & protector, and basically cleaned, derusted and painted it all, mostly with POR-15 except the diff which I used spray paint on, and replaced most wear items.

Every aspect of this was difficult, from undoing tights fasteners that probably haven't ever been undone, to removing the arm bushings (6 in all, I kept the subframe & diff support bushings on as they looked fine and don't affect handling much) and ball joints, to removing all that rust, to painting it all, to getting it all back on.

All working nearly 7 days a week, often under very hot, humid and sunny conditions (so much for shade trees!), under the threat of planned street repaving any day now (I work on the street), and with a pretty sick dad half a world away I'm probably going to have to fly out to see. Oh, and my mom's car died, and they stole the cat from my other car, while all this was going on, so I had to take a bus and walk to get some tools and parts.

But it's finally over!!! Except for this gas issue.
 
Last edited:

1990TSIAWDTALON

Moderator
9,445
5,281
Nov 14, 2013
Independence, Kansas
You are fine. Drive the car. If it see's knock from the 87, the sensor will pull timing and you will be ok (but don't do it again or you have to take a timeout) LOL
 
Solution

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
So the engine won't self-destruct and explode and be visible from space? :p

I'll put 6 or so more gallons of 93 in later today. Should bring the average octane up to 91.5, which I think is ok, right?

This happened to me once before, over 20 years ago, when I lent my car to my dad for a few weeks and he put in regular, and it took several premium tankfuls to get the car back to normal again. But he drove it long distances and I'm just putting 2-3 miles on it till I put premium in to balance things out.
 

1990TSIAWDTALON

Moderator
9,445
5,281
Nov 14, 2013
Independence, Kansas
Yep it will be ok. Don't try any hard driving, just drive it. Take a little road trip to get a little more 87 out of it. Cruising won't hurt it then go get your favorite blend and add it to the tank.
 

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
Ah, so it would actually be better to run down the 87 before adding some 93?

With just under 2 very clean gal in the tank, I guess I'm good for 20 or so local easy miles (mileage wasn't so great pre-overhaul and I'm going to address this later this year so I don't want to push it).
 

1990TSIAWDTALON

Moderator
9,445
5,281
Nov 14, 2013
Independence, Kansas
That is what I would do. If you feel uncomfortable then just take it to the gas station and put better octane fuel in it. I would drive mine with 87 in it, just not drive it hard, like a Sunday drive.
 

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
Too bad. There's a nearby bicycle velodrome that would make a great short circuit track...
 

Kryndon

Proven Member
857
506
Jan 10, 2014
Bulgaria, Europe
You got ECMLink, right? Disconnect your return line from the FPR or filter and turn your pump on manually so it empties most of it in a clean container. Use that gas for stuff like cleaning and degreasing. If you just wanna drive it like that and are worried about knock, load up 2G stock LOW OCTANE timing maps in both HI-LOW tabs just to be sure and drive 'er like that till it runs out.

Our 95 here is closer to your 87 state side and most our cars get tuned for MBT on that much octane. Car still hasn't blown up and always picks it up as a high octane fuel (value 255 in logged items) :idontknow:
 

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
Don’t spend any money on octane booster, just add more premium fuel instead. I would think it would idle fine on 87 so you may have another issue there.
Yes, other issues. Dirty throttle, injectors, etc. I'll overhaul the whole intake later this year, then the exhaust side. Gradually working my way through every system but the engine, which I'm pretty sure is still fine.
 

1990TSIAWDTALON

Moderator
9,445
5,281
Nov 14, 2013
Independence, Kansas
Make sure to check the anti-clunk spring!
 

XC92

Proven Member
1,453
311
Jul 22, 2020
Queens, New_York
Quick followup. As advised I drove it relatively gently for about 1 gallon's worth of miles, then filled halfway with 93, and it's been fine since then. Only reason I didn't fill it all the way is that I'm not doing a lot of driving these days and while prices are coming down they're still pretty high, and I'd rather wait till fall when I'll be resuming driving more.

Well that plus the flux capacitor I ordered hasn't come in yet. :p
 

1990TSIAWDTALON

Moderator
9,445
5,281
Nov 14, 2013
Independence, Kansas
Thanks for a conclusion to the thread, it always makes the thread so much better. Very much appreciated!
When the capacitor comes in, you'll be time travel fast!!! ROFL
Marty
 
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