FJ Cruisers of Northern California

Gas Mileage Becoming Worse?

Hey all,

So during the past month or so, I've noticed that my gas mileage has been getting absolutely terrible. It used to be pretty decent, but now that needle moves to E like it's nobody's business.

To put it in perspective, to drive from San Jose to Stockton, it took me slightly over a quarter of a tank. Now it takes a half of a tank to get there. I haven't made any changes to the FJ at all, I get regular oil changes, tire pressure is correct. The only thing different since I've noticed is that I got the right sized spare put on (but I seriously doubt the added weight of the bigger tire is affecting it that much).

Any suggestions on what to do? I really don't want to take it to the stealership unlessI absolutely have to.

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Permalink Reply by BlackGold1 on September 12, 2011 at 5:26pm

Im watching this thread closely as I am having the same problem.. only getting about 230 miles to the tank! horrible and I keep up on maintenance just like you...

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Permalink Reply by Sonof40 on September 12, 2011 at 5:38pm

What's your average speed from SJ to Stockton?

If you go 60 you'll increase your MGP by at least 2.

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Permalink Reply by Markie Sharkie on September 12, 2011 at 5:39pm

Usually between 60-70mph. I'm not heavy on acceleration or braking either.

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Permalink Reply by Overlander36 on September 12, 2011 at 6:03pm

They may have changed your tire air pressure when they put your spare on. You may have been running slightly high air pressure and now it is set to factory spec. I run 38 PSI - if I drop to the recommended 32 on the door sill, my gas mileage drops dramatically.

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Permalink Reply by Bozly on September 12, 2011 at 6:45pm

Try cleaning the air filter, that could have a pretty good (bad) effect depending on the dust build up.

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Permalink Reply by Bz on September 12, 2011 at 10:49pm

^^^^ and spark plugs too

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Permalink Reply by Lance on September 12, 2011 at 7:18pm

There was a thread on the blue room about a stuck thermostat causing bad mpg. Lots of people chimed in saying they replaced their thermostat and their mpg woes were solved too.

Just throwing it out there. Along with bozly's air filter recommendation check the MAF

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Permalink Reply by daPitbull on September 12, 2011 at 8:11pm

Edit...Nevermind...

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Permalink Reply by Briman on September 12, 2011 at 11:25pm

Same issue here. 230 on a tank of it's all highway and I'm doing 60. 190-210 otherwise. Took it in a few months ago. Would gladly take my $100 diag fee. Damn part swappers can't diagnose a thing. If the diag computer doesn't say anything, they have no clue where to look. It's uncommon to find a dealership mechanic who cam actually find an issue without a code and also one who won't scratch your car.

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Permalink Reply by Bz on September 13, 2011 at 10:44am

gimme a call I can hook your FJ up and I won't scratch your FJ

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Permalink Reply by DWH on September 13, 2011 at 1:08pm

It may also be temperature related. In the last month the weather has been hotter which means the air is less dense and therefore supplies less oxygen to the engine. And the A/C is probably running as well. This may have happened last summer as well but (if I remember right) you did not have many mods done to your vehicle then. The difference with the mods would be more drastic.

Just another theory.