I used to avoid the 10% ethanol stuff like the plague, but I believe it is no longer necessary to advertise ethanol content on the gas pump if it is 10% or less. I have filled up at pumps without the alcohol sign on the pump, and have definitely smelled the alky.

Probably has to do with it being an oxygenating additive now, instead of a fuel stretcher....

George

 

I get about half a MPG less in the winter on the 10% ethanol/gas mix we have here in the winter. And it makes sense because the Ethanol has less energy (BTUs) per gallon then gasoline.

 

[quote=robertbucher;6164012]Last November I got a 2005 F-150 suppercrew with the 4.6L V8. Of the Ford lot it got 15.5 mpg in town and 17.5 on the highway. Looking to do a little bbetter I installed a K&N air filter and a slightly higher profile tire. (Not wider just higher. Tire psi is at 31) I run plus grade gas and change oil at 3k. I change fuel filter at 6K. I have noticed a steady drop in mpg over the last 6 monts. (aprox. .5 mpg per month) I took it into the local ford shop last week and they said they did some software upgrades, cleaned the injectors and again changed the fuel filter. They said according to the compuer it shoul be back at 15 mpg in town. I filled up today and only got 11.9 mpg. Any one have a suggestion? Just to clear things up a bit. All the changes made tires, air filter where done just after purchace. The mpg did not drop in one fill up. The drop as been gradual over 6 months. aprox .5 mpg per fill up. I work nights so I fill up at 10:00 pm or 7 am not a hot time of the day. I use med. grade fuel from name brand stations (Shell, Chevron, Texaco) Tire psi is to factory spec for the tires. Tires are factory spec from Ford. (+ Zero size increse) Ford says their is no codes being thrown so nothing is wrong I am looking for beyond norm problem.

 

Just a stupid thought on my part,A lot of folks over oil the k/n style filters and that gets in the mass air which runns hotter and tell engine its running at a lower rpm.But you are not at that rpm and now your truck sees other sensors more to determine fuel rate.Look at your filter box and see if you can see any excess oil if you can clean filter and mass air then retry your milage.

 

dont know how everybody is getting 13 14 15 mpg when new sticker was
11 city 14 hwy i have a 05 5.4l crew and get about 10 city

 

Checking gas mileage tank to tank is going to give you wacky results. Check it over at least 500, pref. 1000 miles. That's not so say in this case (op) you shouldn't go looking for issues like tire pressure, brakes dragging, problems with the maf, which it sounds like you've done. Check again. Also, the longer term test evens out the cold/hot gas thing.

imo the hot/cold gas thing is a red herring. It's been this way forever, and the cost to "fix" the problem will end up being passed on to the consumer.

Also, a previous post mentioned MTBE as an additive. No longer in use. Leaking tanks (wtf, the let 'em leak after all these years?) spread this poison into the ground water in many areas. Truth be known, with the new engine management systems, late models do not need the oxygenates (sp?) and they probably don't do enough good on the older part of the fleet to justify their use, and they darn sure didn't do enough to clean the air to justify poisoning water. Politics keeps this stuff going, as mandating something gives the producer a license to steal, and part of the profits go back to making sure the mandate is kept in place. One of the grandaddies of this kind of thing:

Green Scissors 2002 Mohair Subsidies

Mohair today, ethanol tomorrow.....

So run it a while and check it over a longer sample. Good luck.

 

He did say in the first post that he was comparing milleage drop over 6 months...

 

K&N probably did nothing.
Larger tires hurt gas mileage
Higher Octane fuel does absolutely nothing. The wifes tail about it cleaning the engine and making it run better and get better gas mileage is full of bull.
IF anything higher octane will cause more carbon build up b/c your truck will only burn 87 octane, and no more, so the rest is just a waste of money.

Slow acceleration is key to gas mileage in these trucks. Drive like there's a egg under the gas pedal.

For the 04 in my Sig, I get 20 MPG frequently on hwy trips because I take my time getting up to speed.

 

IF your truck came with the normal 255/65/17s and you went with what I guess is 275/60/17s, it really shouldn't matter much b/c the drop from 65 to 60 will offset the upsizing of the 255 to 275. A 275/65/17 isn't that common of a tire. I would think you would have more pep and mileage with the 275s, if it's the 60 series. I considered this but the 60s on the F150 didn't fill the wheel wells good enough. Me likey macho look better.

 

I went from 265x70 to 285x75 (both R16, 30.6" vs 32.8") and also pickup up 80 pounds extra rotating weight (20 per corner) and didnt notice any worse gas milleage. And thats even with the 4.2L and highway gears, a combo which it should effect the worse. And yes I have taken into account the spedo differences, even verified on GPS. Of course with the standard deviation you normally get, its hard to see small differences so in all honesty it could have changed but by less than .5 mpg at the very most.

 

How does the engine know to burn only 87 octane and nothing higher? That doesn't make sense to me. I would think that when the spark plug fires everything in the combustion chamber is going to burn regardless. Once I finally get all my spark plugs changed I'm gonna run shell v power because of the higher octane rating (93) and it also has 5 times the cleaning solvents required by top tier fuel.

 

The engine is designed for 87 octane. You will get NOTHING from higher octane gas unless you have a programer telling your computer to take advantage of the extra octane.

If you want to waste your money, have at it. I know I won't.

 

Octane is flame retardant, meaning, the higher the octane the slower it burns. What that does for you is basically this:

timing on your truck is set to ignite the gas inside the combustion chamber at 10 degrees before top dead center (aka piston fully up). your cylinder will compress the air/fuel for a bit more, after that, the explosion of the gas pushes the cylinder down. What higher octane does is basically make that flame less violent. The higher octane can be made just as violent if you compress the air/fuel inside the combustion chamber a bit more (in the end, you'll end up with more power that way). That's why vehicles with higher compression NEED higher octane. The bad news is, you can't change your pistons all that easy to bump up the compression to make use of the higher octane gasoline/higher power. The good news is, you can change the timing on your vehicle with a tuner, basically making it ignite sooner, and thus optimize the window of time the gasoline has to burn inside your combustion chamber. That's why you see the tuners advertise tunes for different octane gasolines. The bad part about burning premium in a fully stock vehicle that requires unleaded is your engine is expecting a more violent, quicker explosion out of that gasoline, and is allowing a too short window (and/or not enough compression) for the premium gas to burn. Thus you get less of a burn, and hence why people are saying you're throwing money away. VCT confuses things a bit more so I left that out on purpose.

as for the cleaning solvents part, replace your fuel filter, and clean your injectors (professionally by having them run concentrated cleaner through them, not the crap you put in the tank), should be all the cleaning needed. If you have other crap in the combustion chamber that got past the fuel filter and injectors, you've got other problems.

Hope this helps.

 

Ahhh ok, dur dur dur, THAT makes sense, guess I was having a newb moment earlier. Thanks for clarifying.