What's going on all. 97 SE Disco here for those who don't know. I was away for 5 weeks in Switzerland working/taking a class and when I got back my roommate had not started my car at least once a week or so and let it run like I asked. Anyway, I felt like my MPG wasn't averaging what it should so I decided to try to monitor it and I'm actually shocked at what I found.

At 1/4 tank (our tanks are 23.6 gallons or so correct?) I was at 64,900 miles. The indicator light lit up a bit ago and I'm currently at 64,923 miles. If this is accurate, at about 64,930 i should be near being out.

Now I realize cold starts and flooring it can use up a lot of gas, but for one, I live in Los Angeles (even without letting it warm up engine doesn't get too cold during the day), and I never really go to fast. Most of these were city around 30-40 mph, but even on the highway when I wasn't checking I couldn't have averaged more than 9-10MPG as I literally devoured a quarter of a tank, which is what made me notice this problem.

There are no check engine lights, car has been running fine (besides the strange slight surging with my a/c on when I release my accelerator at 60-70+, but I believe that is due to an overdue a/c recharge). I checked all my fluids, tranny fluid is still light pinkish, and though I'm overdue for an oil change (last changed around 60,500miles), I'm not THAT overdue, and last time I did it I did an engine flush. No strange smells, I've literally checked everything I can for now. I no longer live in my house (moved to an APT. Complex. and a large portion of my toolset was stolen from our old house's backyard), so I don't have a garage, but I changed plugs, wires, air filter, oil filter, brake pads, bearings, etc. at around 60k.

I was thinking O2s after searching and seeing some other threads, but I mean I have no check engine lights or engine difficulty. I may have to have my mechanic look at it, but at this point I'm truly at a loss. Does anyone know about this? I'm averaging like 5-8MPG it seems, which is pretty ridiculous.

 

Could you possibly have a lose vacuum hose?? Or a hole in one?

 

I'll check that when I get out of work atan, but I don't think so. I popped the hood yesterday and did a quick inspection, but you never know, I may have missed something.

The only thing though, and correct me if i'm wrong, but wouldn't my engine be running strange (besides guzzling gas)? My engine's been running beautifully over the past week, but from what I know, if my O2 sensors were shot this wouldn't be the case either so I really don't know. I'll get back to you with the vacuum hose info. I don't have the rave on me here at work, but thats that tube that connects to the engine by the IACV correct?

 

While you are under the hood check the air filter, in case something built a nest while you were away. Are you getting up to a speed where 4th gear (overdrive) really engages?

 

Are you just measuring your gas mileage based on that 1/4 tank? That will NOT give you an accurate measurement of your mileage since it sounds like you are 'guesstimating.'

Fill 'er up, reset the trip counter and try again.

EDIT : May have misread your post. So you got 23-ish miles to your WHOLE tank?

 

Did that yesterday, no nest, I even re-set it since it seemed like it was slightly unflush.

ylo, I will likely do that before taking her in, and normally I would agree with you, but I had slightly over 1/4 tank when I started paying attention. As of now I can't have more than 15 miles left (if I'm lucky). I just dont want to go spend $110+ in gas for it to run out within a week, but I really may have to go with that advice to pin down exactly how much i'm losing. I get out soon so I'll let you both know what I can do, but I've got a few bills and university things to get squared away so i may not have the luxury of filling it up and replacing the O2 sensors in the same weekend if need be if I go this route.

 

Put a scanner on it. I'll bet your O2's come up bad. My service light doesn't seem to ever want to come on, no matter what problems I have.

 

I think I may have to. After checking the vacuum hose near the IACV and all the others that could have an effect on this (I believe) there were no visible issues. I really think it's gotta be the O2s. My other thought was that perhaps the meter is just reading it wrong (although I've always waited for the car to warm up fully to judge wherever my gas levels are at), but I don't really want to take the risk of testing that theory out and ending up gasless at work or something of the sort.

 

Here is a tip from your Uncle Spike, if you never let your gas tank get below 3/4 of a tank it hurts less at the pump, instead of spending $120 you will spend $30.

Your a/c "being over due" for service is BS, the a/c has nothing to do with anything other than keeping you cool and will not cause any engine run issues.
Do NOT have your room mate start your truck once a week and let it idle, you are just wasting gas and rotting out your exhaust as well as fouling your spark plugs and O2 sensors.
When a engine is cold it runs rich, meaning it uses more fuel and all of that extra fuel gets dumped down stream and unless you actually drive the truck it will just sit there and collect in the exhaust.
Also all of the water vapor from the exhaust will just collect in the muffler and rot it out.
Either have him drive it for 20 miles once a week or let it sit.
Then once you get home start it, let it idle for 5 min or so and then drive it for at least 20 miles to get everything all nice and hot.
Park it with a full tank.

I park my truck every winter for the month of December, it sits in the parking lot at work buried in a snow bank.
Fires right up first tap of the key each and everytime.

 

Spike, I'm amazed at your Disco. You're an interesting man, haha.