My gas mileage is horrible. I have 150K on my teg, and have never had a prob w/ the mileage b4. I am buring a bit of oil right now, but all of a sudden i have a hole in my exhaust right by the resinator, and my gas mileage has gone down tremendously. Im fixing the exhaust prob this week, but just wondering if anyone has experienced this, or if its something else i should be looking into rather than the exhaust. thanks for the help

 

an exhaust leak will cause your gas mileage to drop...

 

Exhaust leaks at that point in the system usually don't cause fuel economy to go down, but you may have other problems due to the high mileage. Possible items can be clogged catalyst, bad oxygen sensor, valves need adjusting, and vacuum leaks.

The oil consumption, however, would be a better indicator of the condition of your engine's internals. Have you done a compression check?

 

better get a tune up. fuel economy shouldnt drop with an exhaust leak alone. The O2's may be on the way out.

 

Just recently did a tuneup- like w/in 4 months did my plugs/wires/cap/pcv...etc
Never any prob w/ mileage since then until now, I had the car since march w/ like 140K on it and never started buring oil untill 3 months ago when i was only drainning like seriously a quart out after 3k i started to use castrol high mileage oil, and noticed a slight decrease in my consumption of oil. Have not done a compression test yet, but figured that would be my next step. I am replacing the whole exhaust casue its a rusty piece of sh*t right now, so there may even be smaller leaks in it farther up...can i rent the compression test kit?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by teg-your-it &raquo;</TD></TR><TR><TD CLASS="quote">an exhaust leak will cause your gas mileage to drop...</TD></TR></TABLE>

well, it depends where the leak is. If its before the O2 sensors it could drop your gas milage..if its anywhere after the O2 sensors i dont think it really could effect gas consumption.

 

I can share my exhaust leak experience on a 22 yr old Honda Prelude 2.3L. The piping rust through near the muffler, with the muffler completed felt down. I am driving without muffler for 2 days.

I filled up the gas tank, so that I can calculate the exact impact to mpg. This is an experiment I would like to find out how mpg is without muffler. During that time, I was testing ~ 700km/440miles highway, because I was visiting a friend living several hours away.

The highway mpg dropped from 29.5 mpg to 25.5 mpg, which is 13.5% poorer.

After welded the rusted pipe back with a union join, the hwy mpg resume to 29.5 mpg immediately

Fact proven that the combustion engine + catalytic converter requires certain amount of back pressure to work optimum. My best guess is O2 sensor is detecting different values, and causing the ECU mapping to the wrong efficient operating settings, e.g. intake/exhaust valve open too soon/late. In other word, it needs to reprogram the chip in order to tap on free flow exhaust, else mpg will drop