Hello All -

I am experiencing a change in my average fuel economy over the past couple months on my '99 V6 4WD (80K). I was getting about 19-20 on the highway, 17-18 around town. I've noted about a 15% drop in economy, notably on the highway.

I've looked at prior postings, and am hoping for help to narrow down the potential causes:

TSB '99 Fuel Gauge Issue - I bought my Runner with 40K two years ago - how can I find out if the prior owner had the TSB performed? (my gauge does bounce around a bit).

New Tires - This summer, went with Bridgestone Duelers (265/70R), whereas I had 265/75s previously. My intuition tells me there really shouldn't be much of a difference, but can anyone confirm this?

Tuning - About a month ago, thinking this was part of the problem, I cleaned the MAF, throttle body, etc (still very clean from the last time I had done this), and cleaned/re-oiled my Amsoil filter. Additionally, my plugs (OEM) are 1 year old, and look nice and clean (I had expected them to be fouled up). I also reset the EFI fuse. No improvement.

One thing I didn't do was change the fuel filter, and OK, I embarrassed to ask, but where the heck is it?? Should I replace at 80K miles? Could this be the cause?

Thanks in advance for any guidance, or other theories.

I am experiencing the same problem as of last month. it could be the "winter gas".

as a matter of fact I replaced the OEM tires with the same 265/70R REVO's before I noticed the fuel consumption increase.

I also cleaned the MAF, replaced the AMSOIL, reset the EFI and I will try to replace the plugs tomorrow.

the fuel filter is located right about underneath your butt, you can't miss it if you look under hte car.

w.

>>>*Every single one of my vehicles dropped about 12-15% this Fall, just like they do every Fall.

Oxygenated fuels, of course....Could be as simple as that.. Check the pumps where you buy fuel, see if they says "Contains Alcohol"...*EB

I checked the pump at my latest tank up - sticker noted 10% ethanol content. Could this be the sole cause of the drop?

Since you got smaller tires, your fuel economy should go up. 10-15% lower than 19-20 highway is about what I get on my SC'd runner.

The difference in fuel is an interesting theory... I'd like to see what other people say about that.

regarding the tires - I figured the smaller tires would throw off the odometer, showing less miles traveled than actual. however, I checked that on a recent trip of known distance, and I am definitely using more fuel than on prior trips.

Hey guys... I'm new to the board, but trying to get caught up as quickly as possible. I bought a '98 SR5, V6, 5-speed in November and have used this site to answer a lot of questions.

I have not heard of resetting the EFI fuse... can someone explain this? What are the symptoms? By the way, I'm averaging about 17mpg for my first couple of tanks.

Thanks a lot!
Dave

Hi, dsalvetti. I just saw your post -
The EFI fuse is located in the engine compartment fuse box - you can't miss it. By resetting - I simply mean that I pulled the fuse for a half a minute and reseated it - I've done this before to help clear OBD II trouble codes. Probably not really applicable in my case, but I did it anyway.

I threw in some valvoline fuel system cleaner, and have slowed down a bit <img src="/forums/images/graemlins/evil.gif" alt="" /> on my last long distance drive - MPG a touch higher 17.6 - but still not where I was at before. Looking to change the fuel filter next. Hopefully it's just the winter gas.