Lower miles per gallon

[Dick Langendorff]

The last couple of months my mileage has gone from 19/20 down to 16 or so. No change in driving habits.The oil seems fine.On a recent trip with the 5th wheel, my mpg was the same, right at 13. 1300 miles.Last summer we were on an extended trip and I had the same 13 for the 5000 mile trip.Could there be something with a sensor?I can't figure it out.All of the MPG's are done with a hand calc. I fill before I leave, keep track of my purchases and fill when I get home. That way I know exactly what I used.Any ideas?

 

[KATOOM]

Need to know more about the truck. Year, stock, modifications, mileage, history, etc.....

 

[Killer223]

could always be the pumps are off. i can go to my local station and fill my gas can to 5 gallons. sometimes i get 4 1/4 sometimes i get 4 3/4 have to get 5 though. but the meter always reads 5.000 gallons. so just an fyi...

 

[p-Bar]

How are you pumping? ? pump till it shuts off? or top it all the way off ? which takes a lot of time

 

[Prairie Dog]

With everything running fine it's awful hard to tell whats goin on.
I have a similar situation where it seems like my trucks exhaust started to stink a lot more at idle the last couple of years. I even had a bum comment on it the other day!
But it doesn't smoke and just passed emmissions testing.

 

[KATOOM]

could always be the pumps are off. i can go to my local station and fill my gas can to 5 gallons. sometimes i get 4 1/4 sometimes i get 4 3/4 have to get 5 though. but the meter always reads 5.000 gallons. so just an fyi...

Whoa..... This is nothing to take lightly. If you ever think your fuel station pumps are inaccurate then call weights and measures. These places are supposed to be closely monitored.

 

[Hoefler]

Exactly!! In Missouri, you have to pump 1155 cubic inches for 5 gallon of fuel, You CANNOT be off more than 1 cubic inch either way!

 

[MarkEkberg]

I have often wondered about the pumps. I run fuel tanks till empty. I know exactly how much fuel fits in our cars. Every once in a while at a different fuel stop I will fit a extra gallon in?

 

[petersonj]

In Missouri, you have to pump 525 cubic inches for 5 gallon of fuel...

I don't think I will be purchasing fuel in Missouri! All the other states have to pump 1125 cubic inches for 5 gallons of fuel.

I am basing this on my experience in the hydraulic industry where 231 cubic inches per gallon is used for calculating reservoir sizes. I am sure that your error is a typo and I agree that fuel pump dispensers are required to be very accurate.

- John

 

[Hoefler]

I don't think I will be purchasing fuel in Missouri! All the other states have to pump 1125 cubic inches for 5 gallons of fuel.

I am basing this on my experience in the hydraulic industry where 231 cubic inches per gallon is used for calculating reservoir sizes. I am sure that your error is a typo and I agree that fuel pump dispensers are required to be very accurate.

- John

My bad. Just did a Google search, we are both incorrect, it is 1155 cubic inches per 5 gallon.

 

[petersonj]

My bad. Just did a Google search, we are both incorrect, it is 1155 cubic inches per 5 gallon.

I used a calculator and observed the correct number and still provided the incorrect information. I even proof read my post.

Thanks for the correction.

- John

 

[jhenderson]

I'd Jack all 4 corners and check for a dragging caliper. It doesn't take much to loose mileage.

 

[jjdiesel]

So....OP.....ever find anything as to your fuel mileage decrease?

 

[Dick Langendorff]

Thanks to everyone.jjdiesel, no I have not figured anything out. Could be more short driving and stop lights. However 4 mpg drop seems like a lot. Oil looks good using a blotter test. Will send in a sample in a month or so. When I tow the 5th wheel, it is the same as it has been for the past 12 years. Around 13+/-.

 

[jjdiesel]

Yes, that does seem like a lot to just get lost without some reason. Did you check for boost leaks?

 

[ProLean]

Mine went down by about 2 mpg when I had my new injectors installed. I bought the Bosch reman. injector on the advice of the shop because he said he would warranty them if I had any issues. Can't figure out why I'm only getting about 16.5 mpg in my normal driving cycle. My #6 was bad and causing issues (CEL and stalling) so we replaced all six at 159k along with the valve cover gasket. The truck certainly runs smoother but does not seem to have the power to tow like it did.

 

[cerberusiam]

because he said he would warranty them if I had any issues.

So, is the shop going to warranty them now that something is wrong?

 

[ProLean]

Cerb,
I don't know that something is wrong...the truck runs very smoothly. I just think that it is not towing as well (ie...hotter egt's ) which may have to do with more fuel being used since that #6 injector is working all the time again? I am not sure if I am just coming from a different experience with a faulty injector. My neighbor even commented that my truck sounds different now. I think there was a definite lope to it before.
Should I take it in and ask them to test it? What test should I ask them to run?
I have a Smarty S-06 on level 4 which is full timing, no torque management, and 90 HP. I run that towing but I'm easy on the throttle because it can get into the 1300* running up a long stretch towing 12K toyhauler. I do not stay very long at 1300* egt so I don't melt a turbo or a piston.
Thanks.

 

[KATOOM]

Remove the Smarty and see if the problem still exists. If it does then I'd have the injectors pop tested by the shop who's warrantying them, and make sure they're not pithy too. If they come back fine then while the injectors are out, have the cylinders compression tested. You may have one thats burnt, and if there is then its likely cylinder 5 or 6.

 

[cerberusiam]

I was being a little facetious with that comment, but, considering what you are seeing for results maybe not. When it comes to the shop actually doing something about it, yeah, it was a lot facetious.

The question to the answer is: what does running good really mean? If one changes ONLY the injectors with the SAME basic injector (ie. not larger nozzles) and the mpg goes down, but, the engine runs smoothly and starts good does that mean everything is fine? Unfortunately, that is going to be totally subjective to ones level of tolerance. You solved the problem with the lope, codes, maybe limp mode, but, now something else is has changed to the negative. Sucks but that is the reality of using reman injectors more often than not. They are cheaper for a reason.

If all you were having issues with were codes for 1 injector, it was a bad solenoid and likely nothing mechanical. From the mpg drop your old injectors quite likely were in better shape mechanically than the remans you have now. That really bites but it happens all the time.

A reman CR injector is really a waste of time, only use in case of emergency to get home. There is little most of these shops can do to test them, they simply don't have the expertise or equipment to do an adequate job of identifying problems. These aren't jerk pump injectors you can pop test and get a warm fuzzy all is good. CR injectors will test good 9 of 10 times and still be bad, the published specs on these things are too broad for a precision engineered component and they will fail to perform adequately when installed.

Fight these junk injectors for a while then get a GOOD set of customized CR injectors to install and the light bulb really comes on bright. You go from "I can live with this" to "WHY did I live without this". LOL!