Fuel consumption?

[crazypj]

Hi Folks,
I keep a log of how much gas I use, just about everything since I bought truck new in 04. (I had to do it when I worked as site service engineer and the habit stuck)
Anyway, my quesion is, I was getting around 27~34 mpg averages until Florida went to 10% ethanol fuel.
(34mpg on highway @ 65~75mph) It only dropped to 23mpg when I had 2,000 lbs in back coming from Pennsylvania (brakes were not too happy stopping from 75+)
Now, I have to drive much slower to get even close to the 27mpg.(55~60mph)
I don't know if its the fuel being lower quality/alcohol added or the urban myth? of vehicle ECM/ECU being programmed to use more fuel after 50,000 miles?
My driving style and distance hasn't changed but my speeds have (up to 30mph slower).
The usual suspects have been checked and all service /wear items/tyre pressures set or replaced.
Any thoughts?
PJ

 

[Wicked_Sludge]

ethanol does contain fewer BTU's per unit than gasoline, so you should expect at least a small change in economy after the ethanol switch. also note that your truck has no way of actively monitoring the fuels octane rating, and therefor you may not be taking full advantage of the ethanols 110 point octane rating.

what kind of mileage do you get now if you were to drive the same speeds as before?

 

[crazypj]

I filled up today, same gas station , same pump, down to 24.8mpg with 'normal' driving (same route to work, etc)
This is way less than I would expect, seems to be getting worse.
Something is wrong somewhere.
The ethanol isn't raising octane to 110, its probably raising the octane of 'diesel' to 87?
Even so, does anyone else know or care about their actual fuel consumption or are they just guessing?
PJ

 

[Wicked_Sludge]

pure ethanol has an octane rating of 110. since its only a 10% mix, your fuel isnt anywhere close to 110, but its still higher than the base gasolines rating.

but your right, a 29% decrease in economy isnt just the ethanol, something is wrong with your truck.

cant speak for anyone else....but i keep a running tab of my fuel economy in all 3 vehicles in an msword document on the computer. besides being able to get an accurate average, tapering fuel economy can act as an early warning system of types to tell you when something is not well with your engine.

 

[crazypj]

I use excell chart but its more or less same thing really.
I was getting between 27~29 mpg even with jaunts up to 85~90,(the 34mpg was a one off on the highway at 55~65) now its down to 25ish at only 50~70mph.
Thing is, I'm stumped what to do next without taking it to a 'stealers' and letting them check computer log.
I have a good idea of what scanning software can do as I work on Suzuki motorcycles and they use proprietary software which gives a lot of information. It allows you to isolate various components in fuel/ignition system and checks all monitored outputs from sensors.
I guess I could check primary peak voltages and see if ignition system has any issues?
The design life of injectors should be around 100,000 miles?
I have an OBD-II code reader but there are no faults showing.
Just to clarify, motor is the chain driven DOHC 2.3 Mazda engine (Made in Japan,so parts person at dealers tells me)
Its also used in a couple of the current Mazda cars?
It doesn't seem to be listed in engine section, only the SOHC 2.3
Anyone have any other idea's?
PJ

 

[Wicked_Sludge]

taking it to the dealership would probably be your easiest option....but be prepaired for them to tell you "its normal". your still getting on the low side of what your setup should be getting, though a significant and sudden drop in MPG is a cause for concern if you ask me.

dont forget about the simple things like air filters, tire pressure, fuel filters, ect.

injectors dont have a set service life. as long as you keep your fuel filter changed, they will outlast you or I. ive seen engines with over 300k on them that are still chugging along with the original injectors.

your engine is called a "Duratec", and appearantly we dont have a section for it in the tech library (guess i should ask jim about that). hit wikipedia up, they have a pretty informative article on the duratec line.

 

[MrShanks2U]

i've personally never used ethanol so i really have no knowledge or experience with it. but i have heard from several reliable sources that even though a vehicle may be flex fuel, ethanol can still cause damage in your fuel delivery system. like i said, that's just what i have heard. so going on that, maybe you should try checking your fuel system.

 

[crazypj]

I don't know if I had bad gas or something (temperatures have cooled off in Florida a bit)
I used some Chevron fuel injector cleaner and truck seems to be running a bit smoother.
Its also gotten 219miles to half tank mark on gauge instead of 187~190 which is a big improvement.
Going to fill up andd check mileage
PJ

 

[crazypj]

Checked consumption and its gone from 23.8mpg, 24.1mpg to just over 29mpg. Except for the injector cleaner ( after I used almost half tank) I haven't done anything which could be remotely considered a service item.
I'm really thinking it was bad gas after hurricanes in Texas, maybe just a bit more than 10% ethanol?
PJ

 

[Wicked_Sludge]

must have just been a fluke. glad economy is back where it belongs for you

 

[kiwi]

I have a 1984 Bronco ll Eddie Bauer manual shift five speed with standard 2.8 six in it. It has never given me more than 13 mpg!! This is in normal street and freeway driving on the speed limit. I asked about this in another forum moons ago and I think Ranger Dave came back with a suggestion to do with the carburetor but I did not understand it and it has gone from that forum so I am back at square one again. Anyone got any suggestions? I cannot afford this any longer with gas prices like they are now. I had the heads planed and cleaned and I think I got 16mpg. Maybe I made a calculation error, on the first run after that, but it is definitely back to 13 now. HELP!!

 

[adsm08]

Anyone got any suggestions?

Start your own thread somewhere appropriate instead of reviving a 3-years dead thread in the wrong area of the forum?