If anyone would care to search for my previous topic on BITOG (Bob is the oil guy) I stated that my mileage has dropped from 30 mpg to 26-27mpg around last fall.

Then it dropped to 25 mpg in the winter. And now that Spring is here, it's dropped to 23 mpg.

Details:

1) 1998 Hyundai Tiburon with 115K miles on the Odo.

2) Two full Auto RX Clean/Rinse cycles performed at recommended intervals. Auto-Rx Info

3) Currently using Mobil 1 EP Oil 5W30 with MB1 EP Filter + ARX Maintainence Dose. Oil has 5K Miles. Also using FP 60 Fuel Treatment.

4) The Cat Converter has been partially clogged since I've owned the car. Nothing new, but it could've gotten worse (waiting on the EQL Headers from Chris)

5) The left wheel bearing is squeeling and needs changing

If this were December, I'd blame the winter blend of gas. But Illinois has likely switched back to warmer temperature gasoline blends.

I'm left with few explainations. All products I use are extremely highly recommended (not snake oil) Please help.

 

its colder in the winter. air is a little denser, so you use up a little more fuel in the process.

fix your damn cat though. wink1.gif

 

Fixing it would have been a waste of $ since back in October, the headers would have replaced the crappy Catheader manifold that I have.

Now, 6 months later, I'm scratching my head wishing I had done it anyway.

But I doubt that would explain the loss. And its gotten warmer and the mileage dropped even further.

 

change your 02 sensors!!!

 

???^^ abq?


I dunno, it makes sense to me that a partially clogged cat would decrease your MPG more and more.....as it gets clogged more .... and more .... until finally you'll have to floor it just to get out of your driveway (then your MPG is REALLY going to suck fing02.gif)

Also, I don't think they've stopped blending the gas yet. Well, here in WI anyway we just got another snowstorm last night. I can't imagine the weather being TOO much different just 200 miles away. Weather is pissing me off, it will be 60s and sunny for like a week, then a snowstorm, then it melts, then its freezing again ...... sigh.

Anyway, between your clogged cat and the gas I think that explains your MPG decrease.


BTW, its the cat that is in your exhaust manifold that is clogged? or the 2nd one? did you ever get the CEL code read?

 

when was the last time you did wheel alignment?

change your bearing and do an alignment..... and get rid of that cat

 

you would be surprised at how much miliage a bad wheel bearing can suck up.

 

Bearing is being pressed on as I type this. $140 total. Dammit!

But I had no idea a bad bearing can impact mileage. Care to explain why?

Thanks

 

^^^ easy, it will be harder for wheel to spin

and your alignment may be changing because of the bad bearing

 

I would blame the bad cat converter. If it's clogged, it can really hurt your mileage and performance.