Drove with at LEAST a quart oil overfill for 150 miles!

Hi all. I had my oil changed a couple weeks ago. 2003 Ford Mustang Mach 1. A day or two later, I started noticing a lot of smoke coming out of the exhaust at times and it smelled like something was being burned. Checked the dipstick, it was at the full mark. I was getting pretty worried that there was an internal issue. Then I found out at the Mach 1 Registry that the dipsticks in these cars (at least in '03 models) are wrong! Full on the dipstick means you’re overfilled. Nice quality control at Ford!

I changed it again, this time myself. Drained everything out, put back in 6 quarts of Motorcraft blend 5W-20 as the manual calls for. Now it reads a little over 2/3 to the full mark on the dipstick. Smoke and smell in the exhaust stopped immediately. The car runs awesome.

My question is, did I cause any damage to my engine? There are only 28k miles on it. I drove it for about 150 miles or so, maybe 200. Even pretty hard several times, before I noticed the exhaust smoke. Not only was it driven hard a few times for a few seconds, but the car has been aftermarket supercharged (Procharger). So a lot more power output than it came from the factory. (about 520 HP at the crank vs the original 305 HP)

I’ve seen no more smoke at all, and haven’t noticed any oil drips on the garage floor. I just worry that there might now be some hidden issue that may rear it’s head later. Thanks!

I would be more worried about damage to your motor from an aftermarket supercharger than from a slight overfill of oil for 150 miles.

You may have some carbon build up on the spark plugs from when it was smoking, but if it isn’t missing, it should clear itself up after a while. You will never notice except that there is a chance the spark plugs might not last quite as long as they are supposed to. Maybe 80k instead of 100k miles.

You might have a little gunk build up on the valve stems too. Use a top tier gas which has more detergents in it to help clear those out.

keith, thanks I was wondering about the plugs. I always put in Mobil 93 octane, is this a good brand to go with? I’ve always used it because it’s near my house, and I’ve never had a hint of detonation with it. Maybe there’s an additive I should put into my next tank to help as well?

VDCdriver, maybe… I know it’s not the greatest idea for engine longevity. From all the research I’ve done on supercharging a 4.6L 32 valve Mustang, it seems that if you make sure you’re not leaning out on boost, not getting detonation, keep the rwhp under around 450, have a stellar tune, and don’t abuse it on a daily basis they will keep running for a very long time. I’ve got the stellar tune. The hard part is not abusing it! I’m working on that. :neutral:

Getting a lot better at it, I only got the car a few months ago and the initial excitement is wearing off so my right foot has been getting lighter.

If oil wasn’t pushing out the top of the dipstick tube it is very unlikely that any damage was done. I have used a file to scratch a line at the FULL level on a great many Ford dipsticks to avoid problems with customers but for many reasons a great many cars and trucks have shown up at my door overfilled and the only ones that caused oil to be forced into the combustion chamber had their dipsticks pushed up by the oil with oil dripping from the tube and even blown onto the hood and fender well.

And believe it or not Ford trucks have had factory specified oil capacities on 4.9L engines ranging from 5 to 7 quarts yet all the engines were identical except for the dipstick. Go figure.

“I know it’s not the greatest idea for engine longevity”

When you order a car from the factory with a supercharger, it is typical SOP for that engine to come with heavier-duty connecting rods and–possibly–heavier-duty main bearings and bearing caps. When people simply add a supercharger–along with its drive system and “plumbing”–but without “beefing-up” the engine’s internal parts, it can be a formula for greatly diminished engine life.

Don’t abuse it??? If your not going to use it, why did you buy it?

@VDCdriver yeah I’m aware. I looked into getting forged rods and pistons, but it just was going to cost more money than I want to spend on it. So, I am just keeping the power at the widely accepted safe level for these engines with stock internals. There is a ton of data out there about it, as you can imagine since these are such popular cars. Can a rod still snap? Sure, but if you check around Mustang forums, it’s next to impossible to find a case where it happened below 480-500 rwhp. I dyno’d at 448 with conservative timing and safe AFR. If the motor does blow, well I’ll have a new block installed. Gotta pay to play I guess. :smile:

@keith Oh I use it! When I say don’t abuse it, I mean not going WOT every chance I get. There is a proper time and place for everything, I still have plenty of fun.

I wouldn’t worry at all about a quart or two over full and the car sounds like a real blast.

I would also strongly suspect that if stock internals gave up on someone it would be because of outside influences such as poor fuel quality, EGR fault, too much advance in the timing, too much Nitrous, or too many WOT passes down the strip.

If you ever get into a block re-do have you considered going with a DOHC 4.6? You can pick those up out of Lincoln Mark VIIIs pretty reasonable and they’re good for 700 horsepower stock from what I hear.
They also have that 4 valve high end breathing advantage and with a supercharger should really scream. It might take a little stuffing to cram it in there… :smiley:

When the Marks first came out in 1992 (model year 1993) a couple of Ford engineers took one to Bonneville, put on some salt tires, opened the exhaust up, and ran 182 MPH on a stock engine with no blower.

@ok4450 Yep, exactly - bad fuel, leaning out from a clogged filter or pump starting to give out, that sort of thing. That will kill a forced induction motor real fast, just have to keep an eye on the AFR + fuel pressure for potential developing issues and watch out for detonation.

The Mach 1 actually already comes with the DOHC! One of the reasons I bought it instead of the GT. Similar motor to the pre-03 Cobras but with higher 10.1:1 compression. I think the cam profiles and heads might be slightly different too? Unfortunately, taking them too much past 450 - 470 rwhp is too much for the cast rods. The ones you’re thinking about that can handle 700+ were the 03-04 “Terminator” Cobra blocks, those things can make some nasty power without opening the engine! :smile:

We actually had a '93 Mark VIII 20+ years ago, loved that car!! If my motor blows, I’m going to see if I can find a new, built 4.6 shortblock that’s reasonably priced. Otherwise, maybe a new 5.0 out of a wrecked F-150 or Mustang.

700 HP out of a stock 4.6 ? The Bonneville car was checked on a dyno and it barely produced 300hp. They managed to get it up to 182 MPH with careful tuning and some aerodynamic “adjustments”…A 2.42 rear gear and they locked the transmission in 3rd gear, direct drive to avoid gearing losses…I hear echos from 1956-1957 when Karol Miller coaxed his Y-block Ford Victoria to a class record at 150 MPH …

@Caddyman He meant if you start modifying it, the block itself can handle that much. Like on the '03 Cobra you can swap the little stock Eaton blower for a big Kenne Bell or Whipple and put down 600-700 without worrying.

If your car is a manual, then you already have a forged crank, the automatic Mach 1’s have a cast crank. But yeah, the only DOHC 4.6L’s to have forged rods and pistons were the 03-04 Cobras. I have an 03 GT with a Kenne Bell 2.1L . Since I have the cast internals and it’s my daily driver, I run 6 pounds of boost. A fairly conservative (re:fat) tune nets about 395 RWHP. Which equates to about 454 HP at the crank, that’s about as far as I’m willing to go on the stock internals.

I will say that reliability has been largely unaffected. I had the blower and it’s associated bits ( intercooler, fuel pump, injectors,etc.) installed when the car had about 60k on the clock, it now has about 135k miles n it, and aside from normal maintence, the only engine-related repairs over the years have been two coil packs.

These days I don’t think there’s a lot to fear about running an aftermarket supercharger as long as you’re buying from reputable company and have a reputable shop do the install/tuning, and you know what’s a reasonable amount of boost for your engine.

The point about the salt flats Lincoln is that it was a bone stock motor. What would it have done with a blower and a little nitrous.

Peruse enough of this and check out the '03 Cobra that put out 670 HP with Cobra cams and 704 with Comp cams on 14 pounds of boost.


Forgot to mention a local guy big into going faster than most others on the planet has some salt flat Mustangs and they’re putting down close to 900 HP at the rear wheels; 1100 at the crankshaft.

I wouldn’t be overly concerned about the overfill’s effects. I would have suggested that you measure how much oil came out when you drained it, but I presume it is too late for that. I might be inclined to check and maybe proactively replace the pcv valve and check all the hoses related to the pcv function to make sure they are not clogged with oil.

I wouldn’t worry either. People who have their oil changed at the quickie oil change places usually get over-filled, under-filled or no-fill. The people who get their oil over-filled usually fall in the “very lucky” category in my opinion.