I'm not sure if this is symptomatic of my clutch slipping, or possible head gasket leak, etc, or both, but my car's last tankful went from it's usual 20-21 mpg, to 17 mpg....

Any thoughts? Coincidence, perhaps??? Help with the diagnosis of possibilities at all, or just further muddy up the waters....?

:dunno

Here's one theory: if your headgasket is shot, that would explain the antifreeze that you smell, as it's being burned in the chamber. Antifreeze is not oxygen sensor friendly; causing the sensor(s) to fail. Your sensors may have started going bad, leading to the poor gas mileage.

Yikes! Thanks, Nick. That's a sobering picture you paint... I checked the oil, and the coolant resovior, there does not appear to be any mixing of the 2. I gotta get the UV dye test done, and then the compression leak down thingie...

I thought maybe my mpg going to hell was just the clutch, but I've had slipping clutches in other cars in the past, and the lost mpg was not this drastic for what feels/seems like some minor slippage...

or it could be possibly your area is using oxygenated gasoline which hurts fuel economy. That's also a possibility. Less $$ than what Nick is eluding to...hey, didn't I say that about someone else?

Well, since smelling the coolant, it's only got 3 miles on it. A private mechanic I trust implicitly is going to take a look at it over the holidays, until then, I won't be driving it much.

If it's good news, no brown frothy mixure in the oil...

Originally posted by NickG
Here's one theory: if your headgasket is shot, that would explain the antifreeze that you smell, as it's being burned in the chamber. Antifreeze is not oxygen sensor friendly; causing the sensor(s) to fail. Your sensors may have started going bad, leading to the poor gas mileage.

Hmmm...I remember when my first intake manifold (with integrated aftercooler) was leaking fluid. I thought it should have been okay since a small amound of leakage probably got evaporated and burned (aka "unexpected water injection"). But now after hearing this, I am thinking about why my LTFT was going weird. Bad 02 sensor...hmmm...

It hasn't been running super smooth lately, I can tell you that, I thought it was mostly the clutch slipping causing that, but it could be more...

I wish I could get that mpg with my car! I ave. around 15-16mpg on mild driving... the gas gauge needs to be around 3/4 tank to get me from my house to the dyno or the light comes on ( 104 miles round trip approx. ) and make a few runs!

:lol: my freinds are complaining when they get 200 mpg per tank with there rex

The leakdown will give you a much better idea of things. The car running in a richer state from the colder ambient temps might be part of it.

Either way hope its not something $!

Not meaning to scare you, but here's my recent experiences.

My mileage went down, car wasn't running smoothly, or making as much power. Also, it was starting kinda rough.

I cracked the head, and blew the gasket to pieces.

It was running rough starting because coolant was filling up the cylinder a bit. My advice, just to be safe. Let your car sit overnight, then pull your plugs and see if there's any coolant in the cylinders. You do not want to try running the car with coolant in there, because it raises the compression a huge amount, and things can bend.

Not something you probably have to worry about, but definitely check the plug holes just to be on the safe side.

Thanks, Jared, good idea, the car has been sitting a lot lately due to the weather here....