Is anyone else gettng bad Gas Mileage?

[MikeT]

I was wondering if anyone else is getting worse mileage with their cars. In my car and my wifes van we are both getting worse gas mileage and I was wondering if the gas companies are adding more ethanol to the gas at the pumps.. I know some say 10% ethanol but can they add more? Do they have to say if they are adding ethanol? Both vehicles are running well and are up to date on maintenance.

What do you think??

 

[Patman]

Even when I run E85 in my truck the delta is not far from 10% (i.e. 15-16mpg on regular vs 14-15mpg on E85). If your fuel filter & air filter are not recently changed maybe start there. Then maybe look at a REAL injector flush not one of these dump it in the fuel deals. I had a 3000GT that got less mpg's than I expected so I cleaned the throttle body, mass air and intake one weekend and picked up several mpg.

I've seen a difference in mpg with the type of fuel we use and the brand. Both my TT & son's A4 Audis are very happy with Shell premium and can drop a few mpg if they eat at a the Chevron station or get regular Shell vs. the good stuff. My F150 is perfectly happy with any flavor and any brand.

 

[truespode]

My ram only gets 9mpg but that could be b/c it is a 1988 318 and I typically drive 80mph highways.

Ivan

 

[_JOE_]

I've been seeing a bit better economy with that Shell V-power stuff. Maybe a mile or two per gallon. Patman had some good advice about cleaning the MAF sensor and TB. These tend to get gunked up over time and can trick the computer into going richer than necessary. If you have a local garage that does 3-step fuel system cleanings that can help the MPG's if you have carbon build-up. Those kits will include a throttle body cleaner, in tank injector cleaner and a vaccuum induced combustion chamber cleaner.

How many miles on the cars? Sometimes O2 sensors can get lazy and cause a false reading to the ECU. This is usaully in higher mileage cars.

 

[MikeT]

One has 171,000 ( Honda van) and the Accord has 264,000 on it. Don't think because they are old that they should get bad mileage. Up until about 2 months ago, the Accord was regularly getting 25-26 lately it has been getting 22-23. The van was getting 22-23 last two months we are looking at 17-19. Since both had a mileage drop I thought it might be the fuel.

Patman may be on to something. Neither has had a fuel injector flush from a garage. Both have had pour it in the tank stuff though. Both run Excellent so I just never thought of the fuel injectors needing a cleaning.

 

[Patman]

You could always try to SeaFoam them. About $8 a can and has given me good results on a few vehicles. I usually run at least 1/2 a can through the vacuum line straight in to the manifold. On the Audis I actually us the front & rear ports. Gotta' let it suck in the stuff slow and then shut down and let it sit for an hour or so. Fire it up and prepare to kill every flying insect within 1/2 mile! Once it's cleared out you should notice some improvement. I typically do this right before an oil change and then run the other 1/2 through the crankcase in the driveway for about 30 minutes. It's one of those crazy snake oil sounding things that actually has worked on several instances for me.

Won't do much for the injectors but sure cleans the crap out of the intake, valves, piston crown when run through the vacuum and cleans the guts out pretty well when in the oil.

 

[MikeT]

Come to think of it, I did do a can of Sea Foam last year through the vacuum line probably 9000 miles ago on both cars. I also ran a can through the tank to help with the fuel injectors at about the same time... It did kill every bug in sight!

 

[m4i2k2e2]

i am getting horrible gas mileage. i change my airfilter and cleaned my airbox. i bought all new spark plugs and gapped them to spec. still nothing. i dont get it. and i drive 65-70 miles to work ONE WAY. it sucks. i thought it was just my car.

what do you guys mean you ran the sea foam through the vacuum lines? how did you go about doing this? do you dump it in the fuel tank? i have a 2004 explorer 4.0 v6 with 83000 on it. if that helps. thanks guys.

-mike.

 

[MikeT]

what do you guys mean you ran the sea foam through the vacuum lines?

I think the sea foam helps if your car has not been taken care of and needs the cleaning. In my case, the mileage did not go up with the sea foam, I believe because what I have was probably pretty clean to start with.

Is no one else having a recent change in their mileage???

 

[_JOE_]

MikeT is right, you need to have a build-up of carbon for the cleaner to make a big difference.

I haven't noticed it yet here, but we typically get winter blend fuels up here sometime in october that hinder mpg.

MikeT, it may be worth it for you to have the dealer hook the cars up to a scan tool and watch the switching rates of the O2 sensors and verify all the others sensors are functioning properly. My 95k mile 3 liter toyota was getting 15mpg when we got it(had about 85k). After new plugs, mass airflow sensor cleaning, transmission service, alignment, fuel system cleaning and a switch the premium fuel I usually see 19.

Have you had them aligned? New tires?

Some cars can benefit from an ECU reset from time to time. Kind of like your PC likes to be shut down sometimes. All you need to do is unhook the negative battery cable and wait about 5 minutes. Hook it up and take it out for an easy drive so it can set up the most fuel efficient parameters for the ECU.


I wouldn't think BOTH cars would be affected at the same time unless it was some sort of fuel issue though........have you tried a different brand of fuel? What rating do you use?

 

[MikeT]

We sick with (like most) 87 octane. The wheels are in alignment on both as it was very recently done. Since I replaced the starter three weeks ago, I guess the ECU got reset because I had the battery disconnected for about three hours. My trans fluid gets changed every 15,000 miles.

Could it be the summer winter fuel thing? What is the difference? Why would one make the cars get different mileage?

 

[Patman]

Sounds like you take good care of your vehicles MikeT, it sure does pay off in not buying new ones all the time. It really sounds like fuel metering to me. If the injectors are just each a little inefficient then you will see a slight loss of power and thus will be pushing the pedal just a llittle bit more and well you know the rest. I'd start with the mass airflow then a real injector flush at this point, if that doesn't resolve it maybe a trip to a good diagnostic shop to get them hooked up and see where the issue is. It might just be you have a couple injectors that need replaced with that kind of miles on them.

 

[jsantapau]

It seems to me that as the gas got cheaper my mileage went out the window on my car..... truck doesn't seem to see it as bad...

My car has a carb and as strange as it sounds it seems to me that depending on where I fill up my idle will be different and wander around ie... fill up at Chevron it will idle fine and as I go empty it will start to idle up if I fill up at Racetrack the idle will be high and settle down as it goes empty...... the truck has an early fuel management system,simple computer,o2 sensor,& tbi and I never noticed the issues that I have with the carb but the mileage went down some.

the pumps here state that gas contains anywhere from 1% to 10% alchohol which I assume is a pretty significant difference or atleast not very consistent.I kinda figured (no real science just a crapshoot from a 1/2 :moon: observation) that the fuel is different and depending on how sophisticated your fuel management system is ,is directly proportional to how odd you observe things at fill up time.

 

[MikeT]

Sounds like you take good care of your vehicles MikeT, it sure does pay off in not buying new ones all the time.

Thanks! It really does make it nice to not have a car payment

I'd start with the mass airflow then a real injector flush at this point,

Is the Mass air flow sensor something to be cleaned or replaced? I am guessing that this is on the air intake of most vehicles. I will get a Manual for my van, I already have one for the car.

 

[01HondaCR]

I'm with you. I thought the MAF was an electronic piece. Didn't realize you could clean those.

Patman, Do you remember what kinda mileage you were getting in your 3000gt? I have a non-turbo Dodge Stealth and regularly get 22-24. It's rated 18city 22 highway i believe. I know those ratings are usually a joke though. Just seems like most people get less than they are rated so i'm surprised i get more.

 

[_JOE_]

The MAF is a small heated element. The intake air cools it and the computer uses this to tell how much air is coming in. The element can get a bit of soot on it causing the computer to recieve a false reading.

 

[Patman]

Once I did all the usual anal Patman service stuff I was getting 24mpg with regularity.

Like Joe said it's a little wire or grid, the important part is DO NOT TOUCH IT WITH CARB CLEANER! CRC makes a MAF cleaner, it's significantly less caustic. Don't poke or prod the wire, just unplug the unit, detach it and clean it well then reinstall. If you run a K&N oil filter this could be the problem as the oil tends to coat the wire(s), if not there is still enough crud to make a mess of things with that kind of miles.

 

[_JOE_]

I think you meant K&N AIR filter, Patman. And even with a dry element some PCV designs direct oil vapor to the MAF sensor.

 

[Patman]

Yup that's exactly what I ment. :bang: