Flooded my engine, should I change my oil soon?

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Staff member
May 27, 2002
Guelph, Ontario
I mentioned this in the fuel dilution thread but it didn't seem to get much attention so I thought I'd post it on it's own here. Yesterday morning my car (95 LT1 Firebird) would not start, and I made at least two dozen attempts to get it going, it would just crank and crank but would not fire up. Eventually it did fire up, but I'm pretty sure the engine was flooded with gas from all the attempts. I've never smelled inside my oil filler area before, so I'm not 100% sure but it does smell like raw fuel in there right now. I'm wondering if anyone else has ever done this and then gotten a UOA on it to see how much fuel ended up in the oil. I'd hate to end my GC interval so soon, I'm only 2500km into it right now and had planned to go 10,000km. Do you guys think I would eventually end up burning off most of this fuel in the oil due to my long trip to work and back each day? (it's a 25 mile drive, but with rush hour it takes close to an hour each way lately) So should I still take this interval out to 10,000km as originally planned, or cut it in half to 5000km? Or change it now at 2500km? PS-I'm running GC 0w30 and an expensive K&N oil filter, so it's not really cheap stuff I'd be getting rid of. [ April 14, 2004, 10:14 AM: Message edited by: Patman ]
Let me preface this by saying "I'm not a chemist", but here's my take. I realize that gasoline is made of many components, but as a whole, it's very volatile at room temp, let alone at 100C. Also, think about the surface area where your oil is exposed to the air (albeit air coming in from the PCV system). The crankcase, the valve train area, etc. Even if you lost 200cc of gas (I would thing this is an estimate on the high end), I can't see how any would be left in the oil after being swished around for half an hour in a 100C environment. Dave
I am a chemist. I am sure your oil got a larger than normal dose of gas yesterday. My guess is that by the time you got to work yesterday, the gas in the oil was down to what it normally would be. If not, surely by the time you get home tonight. When you do, pull the dipstick and take a good smell. I'll bet it will have the normal oily smell. Also watch the oil pressure gage if you have one. Normal pressure means normal viscosity.
I like the sound of what I'm hearing! I do see completely normal oil pressure, both at idle and at WOT, and nothing seems out of sorts at all with the way the engine runs, it's still very smooth and doesn't sound like there is any more valvetrain noise at all either. I will definitely open the filler cap tonight when I leave work and when I get home and take a whiff to see if it smells different than yesterday. Thanks guys! [Happy]
Drive it. I'll bet 99% of all UOA's that have no fuel in oil are from engines that are used a lot, not short trip driving. The ones that have fuel dilution problems are from short distances. Drive and be happy.
I'm with the rest. The fuel will leave quickly if you just drive it. Just be sure you get the thing up to temp before shutting it down the next few times you have to take it anywhere. Consider 15 minutes the minimum time to have it running each trip. Think how many UOAs we have which show almost no fuel in them. I think the recent UOA posted by Nailz has been the worst to date at 3% and you can tell he made a lot of short trips and/or let his truck sit for long periods. I'd be more concerned about why your ride wouldn't start. Got some nasty junk in your fuel system?? [I dont know] --- Bror Jace
Originally posted by novadude: Why the hard starting? Is your opti on the way out? The only bad thing about the LT1 is that ignition system!
The most common consensus among my LT1 friends is that it's a bad coil or bad coil wire. I doubt it's the opti otherwise the car would stumble at low rpms and/or misfire badly at high rpms, but it does not do that at all, it runs like a champ. Since that episode yesterday morning, it hasn't failed to start up on the first crank, as if none of that happened at all.
I'm not a chemist, but I play one on TV....wait a minute I have a BS degree in Chemistry, so I feel qualfied to....er....BS. Check your plugs? What do they look like? Here's true story, condensed. I've seen this really happen. Car hard to start because fuel (oil) wash off on cylinder walls prevents good compression. No bull. If it does it again, I would change my oil....after I found the root cause. True enough, almost all fuel components will vap off....
Originally posted by Pablo: Check your plugs? What do they look like?
[LOL!] I can't even see my spark plugs from the top of the engine, let alone pull one out to check it! [Big Grin] The LT1 engine is probably one of the single worst engines when it comes to plug swaps. It's generally an 8 hour job for the first timer. [Eek!] For a complete mechanically inept person like myself, it's an impossible task. I'd rather trade the car in than change my own plugs. [Smile]
I'd feel better, taking into account the advice above (fix the problem, pronto!), if I added some LC to it and shortening the OCI. Better safe than sorry. I've driven more miles than I can count on carburetors (never owned an FI vehicle; the Jeep I post about is the wifes), and fuel dilution is a worrisome irritant when a carb is malfunctioning in a non-obvious way. Get enough oil out to look for streaks (so to speak). This was often my way of determining whether (after a lot of tuning and TLC) if another OC was justified. The oil always tends to darken faster with carb (and a points ignition) on an older car. Get 'er fixed, do a UOA and run it out to whatever point you feel comfortable with and run another UOA (as a suggestion), especially if no one else has done such for an LT1. Good luck
Originally posted by novadude: Why the hard starting? Is your opti on the way out? The only bad thing about the LT1 is that ignition system!
I spoke too soon earlier. The car is now displaying classic symptoms of a dying opti. Misfiring badly at WOT right before the redline, and rough running/stumbling at idle when the engine gets hot. [Frown] I'm still waiting on a reply from Terry Dyson on whether or not I should change the oil. He must be out of town right now.
Get that opti fixed ASAP, or you will likely see even more fuel dilution. I was shopping for a 94-95 Z28 when I ended up purchasing my '95 Mustang GT. After hearing all of these Opti horror stories.
Originally posted by novadude: Get that opti fixed ASAP, or you will likely see even more fuel dilution. I was shopping for a 94-95 Z28 when I ended up purchasing my '95 Mustang GT. After hearing all of these Opti horror stories.
The car is at the GM dealer right now. This morning it ran perfectly, I made a number of WOT blasts, but I just didn't feel comfortable driving for too long knowing the opti was on it's way out. I know from other's experiences that when it's on it's way out it misbehaves when hot but then on cold mornings it'll act totally normal. I'm taking no chances. It's really not an expensive repair if you can do it yourself. You can buy a 95-97 vented opti for under $200 US now. The labor is costly if you take it to a dealer since it's probably 6-8 hours by the book. But the experienced LT1 backyard mechanics I know on the net can usually do it in 4 hours, sometimes less. Mine lasted just over 100k, so I really can't complain. It'll most likely be the last one I do, since I doubt it'll die again in the next 3 years/60k that I will own this car before getting a C5. If it dies sooner than that, it'll be my excuse to the wife for getting the C5 even sooner! (believe me, I was tempted to just go get a C5 this morning!!)
fwiw, the oil in all my vehicles always smells pretty strongly of gasoline. yet the UOAs don't show abnormal fuel dilution. -michael
Originally posted by novadude: Yeah, guys can do it in 4 hours, but it took me < 2 minutes to remove the distributor from the 5.0 when I swapped intakes last weekend. [Wink] [Big Grin]
True! I miss the days when I had my 5.0 and if I wanted a bit more throttle response I could just bump that distributor over a little bit and pick up some power for free. I did the same thing on my 95 Escort GT too. Those days are almost gone though, does any new car sold today use a distributor?
I got a call from the GM dealer a short while ago and it could be very good news. They found that the coil wire was very badly burned, it came out of it's holder and was up against the exhaust manifold. So they are going to replace it and the coil too, and then do another check. Unfortunately no GM dealer in town has those parts in stock, so they probably won't know until tomorrow morning if the problem is solved from these two changes. But it sounds promising to me! My repair bill would be considerably lower. I now think that it might be a good idea after all to change out this oil at 5000km instead of 10,000km though, especially with all the misfiring and backfiring the car was doing yesterday when I was making all those WOT runs. At least that 5000km UOA will be very educational, it'll show me if I got any extra engine wear due to this problem. And it'll definitely be interesting to see if there is any fuel left in the oil by the 5000km mark.
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