[willie b]

Hi all,

I have a 1998 Tacoma 2wd with the little 2.4L engine with about 140K on the odometer. This Summer I put in a K&N filter and new plugs, PCV. The mileage went up to 25-6mpg. I was so happy, I wasn't even hypermiling. Well now that it is cold my mileage has dropped to around 18.5-19mpg. :madman: For gas I use 87 octane from BP. Since then, I have put in a bottle of Gumout complete fuel system cleaner http://www.gumout.com/ourProducts/ReganeFSC.asp because the guy behind the counter said it was ~10X stronger than Lucas which I had previous experience with. At any rate, it still is not getting more than 19mpg. Of late, my wife has been driving it to work only ~5 miles each way and the short trip may be having an effect on the mileage as well. Here are my thoughts.

1. I got some bad gas, or the Winter gas with Ethanol is sucking the life out of my truck.

2. I have a clogged fuel system, but I thought that the additive would have helped by now. I don't remember doing the fuel filter, so it is a likely culprit.

3. My wife needs to drive it hard once and a while to blow out the injectors.

What do I do? Put in a tank of 93 Premium to see if the mileage improves? Try another additive, Seafoam or BG44K? Obviously, I will be changing the fuel filter as soon as I can.

Thanks in advance,
B

 

[spazzy]

5 mile drive, maybe its not getting completely warmed up and therefore not as efficient?

Maybe your wife has been driving like a bat out of hell lately

Anyway...my mpgs also drop substantially in the winter

 

[Renovatio]

Winter gas contains ethanol in it (I believe to lower the freezing point). Ethanol is not as combustive as gasoline, I've seen some figures to somewhere from 15%-30%...30% being E85. As you are experiencing close to a 25% drop in fuel efficiency, I believe that ethanol is the main culprit. Short trips could also play a role, on that note I would drive your truck for an extended period of time once every couple weeks.

Personal experience talking. I have had a 2.7L taco and 3.4L taco both seafoam. Both around 120k and never had the cleaning done before I put one can in a the gas tank, roughly containing 10 Gallons (1.6oz:1gal), and about 1/2 can slowly through the PCV valve. Be-careful if you do it as it creates a ton of smoke, but after all said an done. Got about 1-1.5mpg increase in both vehicles.

About the same time I switched out engine and gear oils to synthetic. No perceived difference with the 2wd 3.4L but the 4wd 2.7L got about 1mpg better.

Toyota has no recommendations for replacing the Fuel Filter, regardless I replaced both in the 3.4 and 2.7. No perceived difference in either taco, but a bit better piece of mind. The 2.7 is kind of a pain in the ass, have to take off the intake manifold...

Since you put a K&N filter in, I would check out the MAF. K&N oil has been known to foul up those sensors and that sensor maybe giving false readings to your ECU. You may want to try cleaning it, they have special sensor cleaner, along with the whole intake manifold while you're at it.

Good luck!

 

[nsomniac]

There is no way an ethanol blend (non E-85) is causing a 5-6 mpg drop in mileage. Gumout and additives are junk, save your money and skip that step. Have you looked at your plugs? That's usually a pretty good indicator of bad gas or a fuel system problem. MAF is also a good suggestion, I had problems with mine in both 3.4's and my 2.7. You don't sound much like a do-it-yourself kind of guy, it might be worth having a local shop check it out.

 

[willie b]

There is no way an ethanol blend (non E-85) is causing a 5-6 mpg drop in mileage. Gumout and additives are junk, save your money and skip that step. Have you looked at your plugs? That's usually a pretty good indicator of bad gas or a fuel system problem. MAF is also a good suggestion, I had problems with mine in both 3.4's and my 2.7. You don't sound much like a do-it-yourself kind of guy, it might be worth having a local shop check it out.

Well you don't sound much like a read-it-yourself guy. If you had read my post you would have seen I did the plugs this summer. The K&N filter is clean I checked that first since it could have been clogged. I will check the MAF befoe doing the fuel filter. As for additives, the do work. I have first hand experience with the Lucas in particular.

 

[mtbikerTi]

It's the 5 miles. The engine will run rich until it's warmed up completely, which likely won't occur in 5 miles.

 

[wheatgerm]

The mileage in my car also drops off significantly in the winter for shorter trips only (work is 11 miles away). The car takes longer to get warmed up completely, including the transmission. If I am on the road for a long trip, my mpg is close to summer-time mpg.

Like those above have said, its more related to your vehicle not warming up as fast as summer time.

 

[pimpbot]

Yep...

The mileage in my car also drops off significantly in the winter for shorter trips only (work is 11 miles away). The car takes longer to get warmed up completely, including the transmission. If I am on the road for a long trip, my mpg is close to summer-time mpg.

Like those above have said, its more related to your vehicle not warming up as fast as summer time.

What he said. Short trips kill your mileage.

Also, watch out for those K&N filters. The oil on those filters can end up on the MAF, making it work poorly, or not at all.

And keep that Lucas crap out of your engine. Any company that thinks that foamy motor or gear oil is a good idea oughta be publicly flogged.

 

[Jayem]

Yep, the point about the MAF is that you have to have it tuned to the airflow. I'm not sure why people think putting a K&N on a car somehow magically makes the milege better (yeah, they always say "MOAR AIRFLOW!", disregarding exactly how the engine works). I have a high-flow intake on my car, a high-flow exhaust, and the engine management software that I use (program) takes the intake/exhaust into account accordingly. It also actually increases power because it steps up the turbo boost and modifies the timing and injector pulse width accordingly.

Point is, unless you have some serious hardware and software, you aren't going to get any milege or performance gain. If it was as simple as just bolting on an K&N don't you think toyota, with their thousands of engineers, would have figured that out? If it's "free milege" they'd be stupid not to.

A. You drive a truck.

B. It's winter.

C. Ethanol, although it's not a huge impact.

D. 5 miles doesn't allow you to cruise for any significant time for "highway" milege, it most certainly causes you to accelerate, and the engine is not going to be very warm.

 

[chansen]

And keep that Lucas crap out of your engine. Any company that thinks that foamy motor or gear oil is a good idea oughta be publicly flogged.

Exactly. You don't need additives these days, unless you've got old gas and you need to add some gas line antifreeze. If a simple additive gave better fuel economy, it would already be in the gas. And anyone who sells solutions based on fuel pellets, fuel line magnets, or "vortex" fins you shove in your air intake, should be shot. Daily.

 

[zx1100]

I've been calculating my gas consumption the past few years whenever I fill up my tank and have noticed that in the colder Winter months I get, on average, 2 -3 mpg less than during the warmer Summer months. I regularly drive 70 - 100 miles a day on the highway and nothing done differently to the car.

 

[nsomniac]

Well you don't sound much like a read-it-yourself guy. If you had read my post you would have seen I did the plugs this summer. The K&N filter is clean I checked that first since it could have been clogged. I will check the MAF befoe doing the fuel filter. As for additives, the do work. I have first hand experience with the Lucas in particular.

Wow, for someone who comes on here asking for help, and has only tried additives (which every reputable mechanic not trying to sell you something will tell you are complete ********), I would think you would use less mouth and more ears. You used gumout which is worthless after listening to a guy behind a counter who just sells the stuff claiming it's 10 times better than the other stuff that doesn't work. Pure genius right there. Then you wonder if you got bad gas. If you re-read my post, you will see that I asked if you have looked at your plugs. I didn't ask if you had replaced them, because I already read you did it in summer. The problem has occurred since then, and the best way to tell if you got bad gas it to check your fuel filter and plugs. That would probably have happened after you got your new plugs, since you were getting much better gas mileage when you replaced them, huh?

Here's my advice - as others have said, it could be the weather. I was clear that it is not ethanol. Your fuel system could be fouled, along with the MAF. Any way you look at it, there are multiple areas to investigate before settling for the weather theory.

And one last thing - when you don't know very much about cars, come onto a forum and ask for help, and someone who knows a lot more than you about cars tries to help you, it's best to listen and ask questions. Otherwise just go down to autozone and let them sell you some STP fuel treatment because it's 8 kajillion times better than gumout, and you'll keep having the same problem.

 

[willie b]

Wow, for someone who comes on here asking for help, and has only tried additives (which every reputable mechanic not trying to sell you something will tell you are complete ********), I would think you would use less mouth and more ears. You used gumout which is worthless after listening to a guy behind a counter who just sells the stuff claiming it's 10 times better than the other stuff that doesn't work. Pure genius right there. Then you wonder if you got bad gas. If you re-read my post, you will see that I asked if you have looked at your plugs. I didn't ask if you had replaced them, because I already read you did it in summer. The problem has occurred since then, and the best way to tell if you got bad gas it to check your fuel filter and plugs. That would probably have happened after you got your new plugs, since you were getting much better gas mileage when you replaced them, huh?

Here's my advice - as others have said, it could be the weather. I was clear that it is not ethanol. Your fuel system could be fouled, along with the MAF. Any way you look at it, there are multiple areas to investigate before settling for the weather theory.

And one last thing - when you don't know very much about cars, come onto a forum and ask for help, and someone who knows a lot more than you about cars tries to help you, it's best to listen and ask questions. Otherwise just go down to autozone and let them sell you some STP fuel treatment because it's 8 kajillion times better than gumout, and you'll keep having the same problem.

It was the Toyota Dealer that recommended the Gumout over Lucas. I know when I don't know something and it was your insult that got the retort. I appreciate the advice not the insult. Thanks again for all of the help everyone. I really appreciate it.

I drove it on a road trip today and the mileage was much improved. It was not the 25-6 was getting over the Summer, but it was 21 and in the Winter I will take that. I will check the plugs and if they look good I will assume the gas is not the culprit.

As for the MAF, what do the experts recommend as the best way to check it?

 

[adam728]

I'm going to say it's between the winter gas and the short trips.

Winter blend fuel is different from summer (which is really a generalization, because some areas may have 4-5 different fuel blends throughout the season). Contrary to what someone else answered, summer vs winter gas has nothing to do with ethanol quantity. That, and a 30% blend is NOT E85, also wrongly stated. The main difference in summer and winter blends is the RVP, reed vapor pressure. Simplified, it's a measurement of how easily a fuel vaporizes, summer has a lower RVP to avoid vapor lock, winter has a higher RVP so your car will start even when the intake manifold is below freezing.

Anyway, it's pretty common to see a mileage drop with winter fuels. Not usually the 5-6 mpg you are seeing, but 3-10% is pretty common.


The BIG problem is the short drives. A cold engine is very inefficient, and depending on the EFI control it could be staying in an "open loop" that whole time, which means its running quite rich the whole time. Another issue with cold weather is letting a vehicle warm up. If you or your wife starts it up and waits 10 minutes before heading out, that's 10 minutes of fuel being burnt at 0 mpg. With short trips you'll never average that out.

Im with the others here that say most fuel system additives/cleaners/treatments are basically worthless. They are up there with Jiffy-Lube engine flushes, magic "friction eliminating" oil additives, etc. You'll rarely find an auto manufacturer recomending any of these things as fixes.

 

[Renovatio]

This page has some instructions to cleaning a 3.4L MAF. I'm not sure if there is a difference between the 3.4L and 2.4L MAF but it should give you a general idea.

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.htm

Im with the others here that say most fuel system additives/cleaners/treatments are basically worthless. They are up there with Jiffy-Lube engine flushes, magic "friction eliminating" oil additives, etc. You'll rarely find an auto manufacturer recomending any of these things as fixes.

Respectfully, I disagree. While I agree that engine flushes are useless; I have used, seen, and felt the effects of Seafoam. While the photos you see of the dirty "gunked" valves are often greatly exaggerated, a good additive can go a long way.

 

[willie b]

This page has some instructions to cleaning a 3.4L MAF. I'm not sure if there is a difference between the 3.4L and 2.4L MAF but it should give you a general idea.

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.htm

Renovatio,
Excellent link my friend. That is some great and easy advice. I will see how it goes this Winter, but do you think I should do the MAF cleaning before the CEL error occurs or wait?

I was considering the elbow mod. and silencer removal on the air box and intake, but was hesitant after the mileage dropped. Is there any reason to wait until Summer to do these basic mods? I know I will need to remove the fuse on the EFI or I may get a CEL error.

 

[Renovatio]

Renovatio,
Excellent link my friend. That is some great and easy advice. I will see how it goes this Winter, but do you think I should do the MAF cleaning before the CEL error occurs or wait?

I was considering the elbow mod. and silencer removal on the air box and intake, but was hesitant after the mileage dropped. Is there any reason to wait until Summer to do these basic mods? I know I will need to remove the fuse on the EFI or I may get a CEL error.

I say do it before. No reason not to do some preventative maintenance and there no guarantee that the MAF will trigger a CEL. I haven't cleaned either the 3.4L or 2.7L MAF, its on the to-do list, but no CEL as of yet.

I think I know what you're talking about with the elbow mod. Removing the excess plastic on the airbox? I would call it a snorkel but it doesn't give you any height benefit. I've removed that part anyway, no perceivable difference in either mileage or performance....not that I was expecting any. But you can do it to simplify things, makes the airbox assembly look a bit cleaner.

 

[pimpbot]

Unless...

Exactly. You don't need additives these days, unless you've got old gas and you need to add some gas line antifreeze. If a simple additive gave better fuel economy, it would already be in the gas. And anyone who sells solutions based on fuel pellets, fuel line magnets, or "vortex" fins you shove in your air intake, should be shot. Daily.

... you are trying to treat a specific issue. If you know you have dirty injectors, sometimes some Techron or Berryman Chemtool additive can free them up, but you shouldn't add it all the time. It's really a more hail mary move. If you have dirty injectors, you are probably going to have to replace them anyway.

I don't really get K&N air filters. The air filter is not the most restrictive part of the car's intake... its the intake runners.

 

[Jayem]

As for the MAF, what do the experts recommend as the best way to check it?

It's highly unlikely that your MAF is dirty. My experience with the MAF sensor is that it is usually all or nothing. What is much more likely is that you've screwed up the readings with your K&N system/intake. The system was tuned for a certain amount of airflow, which pertains to a certain reading on the sensor. If you have an aftermarket intake, it is likely that you have changed the air flow, in either the amount or just the pressure that is read, which leads your engine management to do things that you don't want it to do. This is one of the primary reasons that aftermarket intakes usually do not lead to any benefit. Even if you did manage to increase the airflow and power, this would most likely be sensed by the EGT and then the engine will reduce power back into normal parameters. The best way to deal with the MAF would be to put the stock intake and filter back in, that would ensure optimal performance for your current engine and software. You could try to defeat the system with a "hot-air" intake, which actually will increase milege because it decreases the available power and increases the temperature of the engine. Most people can't stand any power tradeoffs though (and more wear due to heat-soak), but unless you are decreasing the power or increasing the temperature of the engine, you aren't really going to increase the efficiency.

Have you heard about putting nitrogen in your tires?

 

[willie b]

It's highly unlikely that your MAF is dirty. My experience with the MAF sensor is that it is usually all or nothing. What is much more likely is that you've screwed up the readings with your K&N system/intake. The system was tuned for a certain amount of airflow, which pertains to a certain reading on the sensor. If you have an aftermarket intake, it is likely that you have changed the air flow, in either the amount or just the pressure that is read, which leads your engine management to do things that you don't want it to do. This is one of the primary reasons that aftermarket intakes usually do not lead to any benefit. Even if you did manage to increase the airflow and power, this would most likely be sensed by the EGT and then the engine will reduce power back into normal parameters. The best way to deal with the MAF would be to put the stock intake and filter back in, that would ensure optimal performance for your current engine and software.

Jayem,
I'm glad you don't think the MAF is dirty. I am not getting a CEL, so I thought it was fine as well.

I don't have a CAI, I only dropped in the K&N into my stock airbox. And over the summer I did see a mileage increase. So if the computer did not notice, something else happened?? I am going to modify the stock air box as listed above, but I doubt if it makes a huge difference. I like tinkering with it, at least if I don't like the way it performs I can always return it to stock. If I do the mods, I am planning to take the EFI fuse out to prevent a possible CEL.

Thanks again for the 100% Nitrogen suggestion, my current Nitrogen input it only about 78%.