when i got this 4runner earlier this year- i was amazed at the mileage i was getting- i hit the highways towing a 4x8 utility trailer with a dirtbike and some other crap in it and easily got 500+ km's (300 miles) going through some pretty wicked mountain passes. I just did it again this past week with the same load and barely got 400 km's (240 miles). it seems like it smells a little rich but im not sure- i have noticed this for a while now (the crappy mileage) and have since put on new tires (70 to 75's now). I thought if something was up, it would flash a warning and i could just pull the codes- but no light and something is up- ideas for me to start checking?

 

Do a basic tune up, change your plugs, wires, oil and all that stuff.......then see how your mileage is

 

O2 sensor failing but not throwing a code .... yet.

 

x2 but also replace PCV valve, fuel filter, and clean the MAF sensor.

 

i have the records showing all the tune up work done recently (i believe), will have to go check it out. will have to get into it next weekend and check a few other things out

 

if you are going by the mileage on the odometer with the tire upgrade you are going about 105m per 100m and the added weight (more mass) and height (like a mild gear ratio change) of the new tires is going to have an effect. did you also go to a more aggressive tire style too? I also dropped mpg from the tire upgrade and lost a little acceleration.
Just my opinion.

 

Going up our mountain passes I don't see 300 miles and I'm towing nothing and in town with a bit of a leadfoot I'm getting a bit over 260 a tank;my mom gets about 320 a tank on the highway in her '99 Limited and 280ish around town so it actually surprises me you got 300 a tank with a trailer and going up some of those passes.

Was that 300 calculation a regular thing or just one trip then you did a second trip getting the 240?

Witha real heavy foot and using a bit of 4wd and no HWY I can get my mileage to be under 240 but mostly I average the 250-265 with mostly city driving.

 

Winter gas formula could be a factor, too.

 

yep, seeing that you are in Canada that might be part of the problem. Make sure your tires are properly inflated too.

 

I think that has something to do with it as well.

 

tires are properly inflated- gas is no issue, this started happening in august. when i first got this i was surprised gettting 480 km's around town driving. the tires are revo's- i went from a/t to a/t so that shouldnt make a diff.

 

Damn Canadians!!

 

Ok, here goes....

1) Ditch the crappy K&N filter if you have one (Amsoil, Truflow, plenty of better choices)
2) clean your MAF with brake cleaner (plenty of info on that)
3) if you haven't already, change plugs (OEM Denso only)
4) replace front O2 sensor (OEM Denso only)
5) pull neg batt terminal to reset ECU
6) 3 cans of Seafoam in 1/3 tank of gas, run until empty light
7) try another tank of gas and see how you do for mileage

 

I meant to refer to the winter gas.

 

Winter gas is one I agree with for sure. You don't say how many mles are on it but the A/F sensor should be replaced every 75,000 miles. As suggested above it's time for a Major tune-up including PCV, Gas filter,plugs, Clean throttle body, clean injectors and run Tech-Tron through it instead of Sea foam. Sea foam is cheaper for sure but it doesn't work near as well as Tech-Tron. Just a little TLC can go a long ways. Mike

 

Mike, with all due respect I'm not sure what you're basing this info on.

 

X2 or 3 on the winter gas (assuming all else is good to go). In Oregon they are supposed to start selling the 15% ethanol mix november 1st-February. My mileage started to suck a couple of months ago, turned out the DEQ stuck in september first. I drive to montana last week in the Tacoma, mileage went up 2-3mpg...

 

Oregon has done away with oxygenated (ethanol) gas every where except within the Portland city limits. I load and deliver fuel for a living (Shell,Tesoro,Trammo,etc...) so I can assure you the info is accurate. We no longer deliver any oxygenated fuel to Troutdale,Sandy,Gresham,Woodburn,Newberg or any of the other out lying areas. Unless things have changed Arco (which I do not deliver) used to be oxygenated year round to keep costs down. Its worth noting that the OXY gas delivered in the PDX area is a different mix than in previous years (more ethanol I suspect).

One thing many people forget is that the weather actually can have a profound affect on your mileage. I run to bend to deliver fuel on a regular basis and its amazing how much the increased drag of running in the rain can affect mileage even on a 105,000# truck. If I drive centered in the road when there is even minimal standing water (not even enough to see) it kills my mileage (yes we keep track for work). I was turning 370 mile bend runs on 71-72 gallons of diesel in the summer but when it rains I'm using 80-85 gallons for that same trip. The other interesting thing is that you can actually see the increased drag in the boost gauge. If you run down the middle of the road in a rain storm your turbo pressure will be running 20-30 psi to maintain speed when in dry conditions you may run 5-10 psi to maintain speed this is just due to the drag created by the water on 24 tires.

You would think winter economy would be better based on the air density but I guess not.

 

Just the opposite.....the dense air only works against you as you attempt to push the truck down the highway with whatever drag coefficent the vehicle has. Despite the fact that the engine may be making more power with denser air, but don't forget you need more fuel to burn with that air too. There's really no way to win on efficiency in winter, gas mileage goes down, period.

 

Jamie, It's based on over twenty years of trying additives in my vehicles and what worked best and my Mechanics opine as well. There is a world of difference in the power and fuel savings when I use Tech-Tron over Sea Foam. It's not cheap around here, it's about $8.00 for a small bottle. Just ad a bottle to 10 gallons of gas and then go drive on the freeway for awhile. You will see an immediate difference in power and gas mileage. I'm not saying that Sea Foam is a bad product or that it doesn't work, we all know it does but I feel that Tech-Tron does a much better job. Lets face it, most people use Sea Foam because it seems to work for them and a small improvement may mean alot to them and the fact that it's cheap has a lot to do with how many people like it, Mike