Big drop in gas mileage

[Iron Horse Herb]

My 02 4x4 V8 has always got 20 -22 mpg on the highway. With nothing that I know of being different I not get 15 mpg. The truck still runs and drives like it did the day I got it. I do have 160K on it, but it runs great, just bad mileage.

Iron horse

[ThundraSpeed]

20-22HWY!?

The best Iv'e ever gotten was 18mpg Hwy on a 2wk avg filling up 6 times! (Of course I may be a little lead footed) . Have you taken a monthly or just a weekly average? What is your standard "Highway Speed"?

[Iron Horse Herb]

All of the 20 plus was on trips to Florida from Indiana, I used every type of air box mod and air filter combo I couod think of and ran 75 to 80 mph. I checked every tank back and forth and always got the same. Average 21 mpg. In town showing off for my friends I always got 17. And yes I know how to figure the mpg, I know some who look at the gas guage and miles driven and figure from that.

Thanks,
iron Horse

[tempetom]

I'd donate that Tundra to the Smithsonian Institute. Maybe Ripley's Believe it or don't also.

[cupidstoy]

o2 sensor or EGR valve will make your mileage drop. o2 sensors throw a code when bad. don't know about egr valve. also a faulty speedometer would give a false reading on miles traveled. do you always get gas locally at the same pump? sometimes the cold weather throws off the flow meters and causes you to get more or less gas than you think you're getting.

other things that could cause a sudden drop in mileage: stuck/frozen parking brake cable; bad u-joint; low tire pressure; wheel bearing going bad; bearing on alternator, a/c, powersteering pump, water pump going bad. etc.

15 is actually close to what most of us get in the winter. mine went down from 17 to around 15 when i put the snow tires on. i don't think you'll get much sympathy around here for 15! ;-)

[docsg]

Originally Posted by cupidstoy

15 is actually close to what most of us get in the winter. mine went down from 17 to around 15 when i put the snow tires on. i don't think you'll get much sympathy around here for 15! ;-)

Here we go again! I am just totally amazed at these 20+ mpg (don't actually believe it) Tundras. I had an 03' SR5, TRD that I got usually about 13 in town (small town--constant start/stop) and 16 - 17 highway (although I rarely ran a full tank out on the highway). I traded it an bought an 05' identical in every respect to the 03' except for the newer engine and the 5-speed auto. It gets about the same mpg as the 03'. I accelerate from a dead stop very conservatively, drive 70 - 80 on the interstate, avoid passing gear, etc. The new truck only as 6K and I will probably see a little increase as the mileage increases. Everybody in this area who have Tundras seems to have mpg's near mine unless they are constantly highway driven. Maybe its the blend of gas, the weather, or possibly none of us know how to drive.

[Iron Horse Herb]

I don't really give a rats *** if anyone believes me as I am the one who puts the gas in it. I told the story as it happened. I didn't want any sympathy just some reasons I might be getting a drop in mileage, thanks cupidstoy I will look at your suggestions.

[kwilson]

Iron horse, I completely believe you. With my '05 DC, in warmer weather, I get 20-21 mpg on the highway, and 16-18 city. Lately I've had a little trouble keeping my foot of the gas, but when I drive like I'm supposed to, it's not hard to get surprisinly good mileage.

[chinaloy]

It's probably the gas formulation. Most states that experience cold weather go to an oxygenated formula in the winter to reduce emmisions. Typically oxygenated gas gets about 20% worse mileage.

The southern states do not switch, AFAIK.

Just the government trying to help out with the already ridiculously high gas prices.

[Picasso]

Herb,
I continue to experience a similar thing with my truck. My gas milage fluctuates quite a bit. Over the past six months, I have on a couple of occasions gotten 20+ mpg hwy driving and then only reached 17 mpg on the return hwy trip. My city driving mpg fluctuates between the low 13s and the mid 15s yet my driving habits remain the same and I use the same gas station to fill up.

The only other time that I have had a vehicle do this was when I drove my 1990 Acura Integra on IH10 between Florida and Arizona. For some unknown reason, my mpg for the leg that went through Ft Stockton, El Paso, and through to Arizona, I would suddenly get 36mpg. All other times, I would consistently get around 32mpg. I drove that leg four times with the same result every time.

I can attribute the fluctuation in my Integra to a specific location but can't explain my Tundra. There aren't any correlations between my gas milage and maintenance (throttle body cleaning, air filter and plug replacement, etc.) either.

[Chevloray]

I was listening to Car Talk a few weeks ago. A listener called in, complaining about poor mileage. One of their questions to her, had to do with how well the heater was working. It seems, in her case, that the engine had been replaced and everything worked great, until the weather got cold. Her heater was taking a long time just to get warm. They suggested that her replacement engine, from a salvage yard, may not have had a thermostat in it.

So, maybe your thermostat is stuck in the open position, and that would slow down the warm-up and cause the computer to keep the fuel system in a richened condition, causing poorer fuel mileage than you have seen historically.

As for computing mileage, there are people who gauge their mileage by the gas gauge and miles traveled, while others are religious about theirs and only fill up at the same pump, letting the nozzle click off three times (or so), before reading the elapsed miles and tenths. Regardless of how you measure your fuel economy, you are the one to know what you are getting. In my case, my '00 2WD Limited got around 21 on a road trip, without A/C, and running at reasonable speeds, like not over 70, but mostly around 65. Around town, I'm getting a solid 15mpg, but that is with trips limited to 5-12 miles, round trip, with stops in between. It ain't the 24mpg that I got with my 220K mile '91 Celica GT, but I'm a lot more comfortable in it. My '98 ES300 Lexus gets around 24 highway and 18 around town. I'm happy. My '69 C-10 truck is getting about 10, if I dare to guess.

[docsg]

Originally Posted by Iron Horse Herb

I don't really give a rats *** if anyone believes me as I am the one who puts the gas in it. I told the story as it happened. I didn't want any sympathy just some reasons I might be getting a drop in mileage, thanks cupidstoy I will look at your suggestions.

I do believe you it just that it is very frustrating to us Tunda owners who get "crappy" mpg compared to what many of you are reporting. I sent copies of posts of owners that were getting the 20+ mpg to my non-TS friends who own Tundras and they bombarded the dealer with complaints along with me. I had an 03' that was perfect in every way and experienced none of the problems that people were reporting like brakes, etc. However, it never got good mileage (usually in the range of 13 city and 17 highway). I got so discouraged with it after reading the posts of mileages like 16-17 in town and 20+ on the highway that I traded it with 24K on a new 05' with hopes of getting the mileage being reported. But, to my dismay, the 05' gets mpg very similar to the 03' (maybe a 1 mpg improvement in both categories). It now has 6K and like the 03' has not given me any problems whatsoever except for the disappointing mpg. The truck is babied more than my neighbor's Lexus. It is garaged every night and is never put away wet. I try to adhere to the 2000 rpm rule, use only Chevron gas, and Mobil 1 and good filters. I love my truck but after reading these great mileage posts, I am now considering the Titan or going back to GM products. My mpg luck with Tundras is evidently not there.

I do have one consolation in that my 05' Harley gets about 8 - 10 more mpg than my two riding buddies. We all have the same indentical engines (1440 cc), they are all 05's, and have had the Stage 1 modifications (increased flow air cleaner, modified pipes, and the ECU remapped). I get 50 mpg consistently at highway speeds (70 - 80) while they stay in the 40 mpg range. It really p!$$3$ them off and I now I know how they feel.

Finally, I didn't mean to offend you and I'm very proud that you are getting the mileage out of your truck you are experiencing. It is frustrating, but I will never see those figures. My saving grace is that I only have to travel about 300 miles a week (mainly in town) which is about a tank of gas. I will test drive the 06' Titan soon as I have read posts of great mileages from their owners as well.

[cupidstoy]

so far the thing i've done to my truck that affects the mileage the most is the tires. docsg, i would be curious if you are running the stock TRD "offroad" tires rather than the stock bfgoodrich duellers that come on the non-trd package. the difference could be close to 2-3 mpg from my experience.

i realize there are a lot of variables that affect gas mileage, but so far tires seem to be the biggie for me. also, greasing the drivetrain every oil change seems to help a little on the 4x4 but i realize that isn't an option on yours. i also add lucas injector cleaner and upper cylinder lube to every other tank or so and that makes a little difference up to the point it pays for itself but doesn't give any net gain in cost. i buy it in bulk. at least that way i know my injectors will stay clean and at peak running condition.

still, i only get 17 with the stock tires and 14.5 - 15 with the snow tires. that's combined highway and city.

i'm afraid you won't be very happy with the titan unless they've changed 'em alot. i drove a buddy's 04 and the minute you sit in it, you'll feel surrounded by poor fit and finish, cheapo plastic gadgets. don't get me wrong, lots of power and probably a solid drivetrain. hey, i was a nissan man for years. it just seems like they've gone down in quality quite a bit lately.

good luck....

sorry to hear your having trouble at the pump.

[CATiger]

<<<<< jealous of 20+ mpg but content with 16-17 I consistently get. It's a 4x4 truck that kicks ***. I pay at the pump without qualms when I decide to torture the poor beast with daily driving duties.

I remember a thread like this a while ago and people were not aware that one guy was claiming mpg based on his V6 and was getting compared to the V8 trucks.... lol.

Back on topic... as far as checking mpg, as long as you are consistent in your method as herb was, noticing a drop like he did is most likely an indication that conditions have changed or something has gone wrong.

Enquiring minds want to know. I would be inclined to start with the thermostat based on the suggestions above. Of course, starting with a good injector cleaner like Bk44, techron or seafoam might be prudent along with routine maintenance like fresh oil & air filters (might even be due for a fuel filter?) and plugs. Throttle body, spark plugs, etc.

Let us know what you find out, iron horse.

[Tones]

docsg,
I agree with cupidstoy that it probably is related to tires. What tire pressure do you run? I run around 35 psi and get around 17 mpg in mixed city/highway driving with the V8.