Crummy Gas Mileage

Hey guys, getting crummy gas mileage here. Something like 14mpg on a V6. Granted I'm not doing freeway miles here, and living on an island there's plenty of hill climb, but 14 mpg seems ridiculous. My uncle gets 14mpg on his El Camino 454SS. The engine doesn't feel like its running badly, in fact it feels pretty good, but I'm wondering if it could be something funky like maybe the oxygen sensors. Is it possible they'd need replacing without throwing a code? Other things getting done are stuff like changing the fuel filter, air filter and points/plugs.

 

ScottyB, there is a lot of different factors that can cause this, some of which you have already thought of. But A big factor is winter gas mixtures get worse MPG's than summer gas. This could be a partial cause of your situation. But since you live on an island, I don't think they have winter gas so it may not be a problem, and should be fine on that.

1.) I would highly suggest switching out for new spark plugs, 2.) New air filter, 3.) Clean the MAF, Throttle body, Air intake, 4.) Add Sea Foam, etc.

There is many other things you can do to improve MPG's, you can change the fuel filter (which could help), alignment, tire balance, transmission oil, rear differential oil, etc

I don't know if the oxygen sensors will always throw a code if they go bad, but could be a possibility. Hopefully someone can chime in on that.

I hope this helps somewhat. Good luck.

 

How long have you had the vehicle? Is this a newly purchased vehicle or have you owned it for a while? In other words....what was the gas mileage prior to now?

You live in Hawaii? So, I'm guessing....you don't get the winter gas mixtures over there since you don't need it for proper combustion. So I would guess, that isn't the issue.

What tire pressure are you running? Are you still on stock tires/suspension? What octane do you run?

 

Regular Octane, everything is oem spec, parts are oem or oem replacement. Only modification to the truck as of yet are a set of bilstein 5100's to replace the oem toyota bilsteins which were dying/dead (especially the rears). Haven't had the truck very long. Just bought it last month. It gets driven regularly but not for a lot of miles, but the previous owner used it as a delivery truck so it used to. Air filter and Oil/filter was changed recently. I have a set of plugs and wires waiting for the weekend. Changed the fuel filter last weekend. Will be changing the tranny and diff fluid soon.

The truck has 175k miles on it but still runs like a champ. The previous owner took it to the dealer for the maintenance for alot of years, and then to reputable shops for it more recently so I know it's been taken care of. All the records were in the glove box.

The oxygen sensors will obviously be last due to their price and not being a regular maintenance type item. Mostly I was just wondering if that was a big deal. I've seen a bad O2 sensor totally bork some other fuel injection cars' mileage and then on other cars only really come into play when cruising at freeway speed on low revs.

 

i agree with all the above. check the "usual suspects" and tire pressure. if under warrenty i would take it to the dealer. good luck

 

can having your alignment done really help gas mileage?

 

I'm only getting about 15 mpg. My air fuel ratio sensor is bad

 

Yes

 

Whoever said tire pressure I can agree with that. Ill add an extra 5-10 psi for city driving and ill add another 30+ miles to my tank easily!!

Also I have noticed after a good alignment ill get a little better mileage so there is something to that

 

I get about 16mpg 60/40 city/hwy (A/C on all the time), I was expecting worse since my truck is lifted and I got bigger tires. I used to get about 17mpg when I was stock but I always use 92 octane and I drive with a lead foot a lot. There will be a lot of naysayers but on most fuel injected vehicles, using a higher octane does increase power and mpg slightly(its been proven). Also, most of the time the better mpg with higher octane overrides the slightly higher price of the gas. I would recheck your mpg after your tune-up as it should get better. But don't expect crazy gains, its hard to get good gas mileage in Hawaii because its so hot and humid (bad for combustion efficiency) and SO much stop and go.

 

The octane rating of gasoline is a measure of how much you can compress the gasoline before it ignites, not how “good” it is.

 

There percentage of cars that require or benefit from high-octane gas is relatively small and these cars have engines that are specifically designed to benefit from higher-octane gasoline. Keep in mind that just because a gasoline is labeled “high-octane” and costs more does not necessarily mean it is better for your car. Buying high-octane gas is not going to give you better gas mileage which is a common misconception and if your car wasn’t made to operate on high-octane gasoline, there’s really no reason for you to fork over the extra cash for it.

 

I changed the o2/fuel oxy sensor and didn't get any better.. I am getting 16-18.. Neighbor gets 23 with her 2000 4x4 automatic.. I am in the same boat as you.. 2001 v6 4x4 manual..

 

I just changed the o2/fuel ratio sensor and it didn't help much.. I bought it on ebay, it was an original denso part.. It was 1/2 price of the Toyota dealer part.

 

I guess I need to change plugs.. I owned the truck about 8 months, and put 7k miles on it.. It sucked going up hills in south Mo.. I cleaned the MAF sensor, and the throttle body was spotless.. I guess new plugs, and air cleaner are next.. I am still not getting what I want.. I want at least 20 mpg.. Is that too much to ask for??

 

Good luck on seeing 20. Thats pretty high expectations. Especially since it was rated new at 16-19. Maybe if you drive only below 50 mph without any stop and go, then you may see 20+. But how realistic is that for all use.

 

My first post but given the topic and my personal interest I thought I'd chime in. I've got a new 2010 PreRunner, its about to turn 1800 miles, not even broke in yet. I've checked a few tank fulls and have been surprised at the limited variation between "highway" and "City" MPG. That said based on this thread I can't complain one bit. She got 21.5 MPG "highway" only (a run up to Vancouver, BC and back via I5, most time between 60-75 MPH) and 19.3 MPG in and around the Eastside (city traffic). My point isn't to brag but to suggest that the truck and the V6 (auto trans) is capable of more. They're great trucks and your effort should pay off!

 

Based on my Scangauge, I see an avg of 20-25 mpg at freeway speeds (65ish). On the other hand, just maintaining a steady speed at 35, my mpg is pretty steady at 16 mpg on a long straight road. Thats just the way the truck is. I'd be really surprised if you see much better than that with a v6 auto.

A lot will also depend on how much you have to stop and go, as the first gear is really terrible for mpg, as is the case with all vehicles. (a made up example (actual figures vary on driving style, etc): the engine is working just as hard going 10 mph as it does going 60, but your only covering 1/6th the distance)

 

I didn't say that octane was a measurement of how "good" a fuel is. Octane is a gasoline's resistance to detonation. Gasoline by itself is about a 55 octane rating and pure octane is 100 if I'm not mistaken. The less "knock" events that the ECM picks up, the more it can advance ignition timing, etc which does increase power.

I read about a test using 87 and 93 octane in a 2nd gen Tacoma. It was the same truck on a loaded dyno and using 93, it gained about 10 horsepower at the crank. Because the ECM could advance the timing more or retard it less, either way, more power was made with the higher octane.

On the contrary, a common misconception is that using a higher octane(in a car that doesn't require it) will NEVER gain you extra mpg. Whenever I fuel up I always calculate my mpg and I always wondered if I should use 87 since everyone say that there is NO benefit from a higher octane in our Tacomas. So I did my own testing, I was already using only 92 octane from Shell so I already had my avg mpg which was consistent throughout. I then did 3 tanks of 87 octane also from Shell and I had a drop in mpg in all 3 tanks of 87 and I drove the same routes more or less and my driving habits stayed the same. The drop in mpg wasn't much, about 1 mpg, but if you do the math, to go the exact same distance on 87 vs. 92 the 87 actually was a hair more! Also, Shell V-Power has 5x the govt. minimum amount of additives whereas their Reg and Plus have about 2x the minimum. Also I just like the peace of mind that I know my valves and ports, etc are probably spotless. I also like the peace of mind that I can floor it when I want and not have to worry about pinging.

In summary, I don't care what ignorant people say or do. These are my own facts/opinions/preferences, nobody has to agree with them. I'm merely showing a non-mainstream perspective on things to show that not everything is "black and white" and no one knows everything.

 

Hm... I have 01 V6 manual with a lift and 32s and I am getting around 20. On the highway to Cape Cod and back I got 23ish.