Sudden Gas Mileage Loss (1 Viewer)

VidereStudios

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I have a 2001 LX470 that is pretty much stock right now. Almost 85K miles...previous owner drove mostly commuting in Los Angeles before I bought it. I have been tracking my gas mileage for the last two years since I bought it. My best was 18.6 mpg with non-ethanol gas and my worst was 13.4 doing lots of short commuting around town.

This last fill up this morning netted me horrible gas mileage...8.7mpg. All the driving on this tank was commuting around town. I don't sense any change in the power of the LX...seems to rev consistently and with no real deviation in RPM's since I bought it. No fuel smells in the garage...

I have replaced both front O2 sensors in 2010...otherwise, nothing done to the exhaust or intake systems. Stock tires for now, no additions in terms of bumpers, etc. Actually, the only thing I did in the last few weeks on the truck was remove the battery to replace the headlight bulbs.

The 90K service has not been done as I was planning on tackling that this summer. I searched through the forum and found that it may be the catalytic converter. Before I go down that road, I wanted to get some feedback from the experts here. Any specific tests I should run? Any thoughts on what the issue could be?
 
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Any thoughts on what the issue could be?
Yes, it is a big heavy vehicle with a V-8.
Seriously, I think you answered your own question with the part about the 8mpg tank being all in town driving. These rigs really suck down the gas in town and the only way to get the average up is to hit the highway and cruise at a judicious speed. The winter blend ethanol gas doesn't help with the mpg's either.
 

tabraha

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I've never had an 8mpg avg tank, even when I lived in Houston traffic. Somethings not right. Most likely you got some terrible gas from somewhere last time. Fill up somewhere else and see what happens. Check to make sure you actually filled it up too. I've had one time after offroading my gauge didn't read accurate for awhile. I believe the float must've gotten hung up but unstuck itself eventually.
 

VidereStudios

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Well, the problem is that I have had all in town driving before...that was in the 13-14mpg range. This sudden drop is gotta be a problem. I hear you on the winter blend ethanol...don't like the stuff.

I am thinking the bad gas could be a possibility. I also found in another post that one guys center differential was locked and the light wasn't indicating that on his dash...mpg suffered greatly. I am going to see if that could be the issue when I drive home tonight. Doubtful though...

The possibilities as I see it right now are: bad gas, center differential was locked for three plus weeks, or there is another issue going on.
 
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8 mpg is not normal, no matter how you're driving, or how loaded (short of pulling a trailer I suppose).

My 100 weights approx 7,400 with everything I have on it (bumpers, rack, loaded drawers, winch, etc.) and I average 12 mpg mixed city/highway.
 

TheFuzz

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Sudden marked drop in mileage? This is a trademark 02 sensor precursor, but since you just replaced them I'm thinking either A) a bad batch of gas or B) one of the 02's that you replaced is faulty. What brand of sensors did you replace the 02's with?

We can't chock this one up to the landcruiser being big and heavy. 12-14mpg? Sure. Thats what I average at altitude with crappy ethanol-polluted gas with short commutes on a stock truck. 8mpg? Short of pulling a yacht, something is wrong. I've NEVER gotten milage that low, even driving like a jackass.

I say drop some fuel treatment in there and fill it up with the best gas you can find, from a busy gas station that gets fresh stuff in their tanks often, and run it for a week or so and see if your mileage stabilizes. If it doesn't, then we can start troublshooting other stuff.
 

TheFuzz

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I have. It involved the CDL, 20"+ of snow, and a lot of counter-steer for many hours. :flipoff2:
Well this is normal people land, not Loudsville where we all countersteer in heavy snow for hours at a time. You are in a world of your own my friend. :flipoff2:
 

VidereStudios

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Sudden marked drop in mileage? This is a trademark 02 sensor precursor, but since you just replaced them I'm thinking either A) a bad batch of gas or B) one of the 02's that you replaced is faulty. What brand of sensors did you replace the 02's with?
O2 sensors were replaced with Denso units purchased online.

We can't chock this one up to the landcruiser being big and heavy. 12-14mpg? Sure. Thats what I average at altitude with crappy ethanol-polluted gas with short commutes on a stock truck. 8mpg? Short of pulling a yacht, something is wrong.
Yeah, definitely. That is why it is so strange...no trailer, no heavy mods (yet). Anyway, doublechecked the CDL on my drive home last night...definitely not that. CD was definitely not engaged.

E-brake stuck?
Doublechecked that as well...nope.

Well, I am going to monitor this over the next couple of weeks as I go through this next batch of gas. I will post updates to this as I go through it. Right now my bet is bad gas. We'll see...
 

VidereStudios

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Well, final update on this. I filled my gas tank up this morning and got to work and calculated the gas mileage. 15.3 miles per gallon on the exact same type of driving I did where I had the abnormally low gas mileage.

Truck continues to run absolutely normally...nothing I could catch. Looks like I will chalk it up to a bad batch of gas. I talked to to the gas station guy I regularly go to and am friendly with...he was doubting it was the gas.

So I will continue to monitor it, but at this point, I won't stress about it. I will be tearing things apart anyway soon for the 90K service.
 

bamabrock

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Just buy top tier gas. I stick with chevron, BP and Shell. I've had too many problems over the years with cheap gas.
 
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They may have overloaded that batch w/ ethanol, which would cause a HUGE drop like you indicated.
 

VidereStudios

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Hmm, good point. I never thought about that. I guess there is room to mess up the recipe...either cooking or making gas!
 

VidereStudios

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Another quick update...15.8 mpg last fill and all commuting miles in town. Not bad. Bad gas is my final answer.
 

hoser

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Will bad gas give you terrible fuel consumption while everything else is fine? (power delivery, idle speed, no roughness, etc.)

If it would've happened to me, I'd chalked it down as bad math, short filling the first tank of gas or a combination of the two.
 

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