kammj

I recently just got an oil change and ever since then my MPG has been unreal.. on the computer usually i get around 17.2 L/100 km. After the oil change its sky rocketed to 24.3 L/100 km. Anyone know what happened? And is there a way i can get the 17.2 down? I do only city driving 90% of the time but that is ridiculusly high as well. Any help would be appreciated

bigmike06gt

Try cleaning your Throttle body. I noticed my mileage dropped quite a bit last month and saw that advice given on here, my mileage is right back up where it belongs again and it was easy to clean.

aaquib1992

+1 to cleaning the TB. An 05 with a never touched TB will probably be horrendously dirty/sticky.

Replace your fuel filter (there are numerous DIY threads with pics on this forum) since that needs to be changed every ~50K miles anyway. And check your tire pressure while you're at it.

What mods (if any) do you have currently?

Ford-a-tude

You had it done at a quick change place? What weight oil did they use? The spec is 5w20. Using a thicker oil will increase the resistance to turn the internals. These modern engines have tighter tolerances so the oil needs to flow easier. Most of these places employ kids that know nothing about cars. When I used to go, they would always ask me what weight oil I wanted. I always told them to read the filler cap where it's printed. Duh.

Nuke

There are many things that can cause a major change like that; some mechanical and others not. If you filled up with a much higher ethanol content fuel, you may be seeing that related loss in mileage. Reset the on-board at the next fill-up but also calculate by hand. The on-board isn't very accurate to begin with.

Did the shop adjust anything? Brakes?

moosestang

Not the tighter tolerances speech again! Show me something that shows this 4.6L 3v has tighter tolerances than any other 4.6L.

I bet you could run 5w40 in these motors with no ill effects. Besides decreased fuel economy and quite possibly less engine wear.

kammj

To answer all/most questions the car is stock other than a Mac axle-back. I have been filling up with 91 octane for the past 4-5 tanks. I reset my computer everytime i fill up just to see what i average for that tanks. They just did the oil, and it was a Ford dealership (i had a free oil change). I am getting a CAI/tune on Tuesday, and cleaning the TB would be a good idea :P. I don't drive hard at all, rarely to be honest. Even at the regular 17.2 i get driving normal why is that so high :S ever since i bought it. The car only has 52 xxx on it

Woodys2718

Hmmm I wouldn't do that (run the improper oil weight) if I were you. The company where I'm employed produces cam phasing valves (VVT, Ti-VCT) for several of today's vehicles. Including the Ford 5.4, 4.6, 3.7 and 2.0 liter engines.

The engine oil weight is VERY important for the proper function of these components. Flow forces, pressure, leakage are all directly affected by the oil weight. Within the cam phasing valve the main components are a body and spool with which electric current by means of a coil moves the spool to allow oil to flow to directed pressure, supply and tank ports of the body. The oil is directed to the cam phaser for cam adjustments.

I work in the QA dept and one of my responsibilities are customer returns. I read countless reports from Ford Technicians stating malfunction due to improper oil weight being used. ie check engine light on, due to improper function of the cam phasing valve... The very first thing they check for is proper oil weight.

I attended a 1 day "engine cleanliness" seminar at the Ford Romeo Engine Plant in Dec. 2010. This is the plant that made the 4.6 3v along with the "hand built" Shelby 5.4 L. It was a basic "best practices" seminar.

Now while I don't have the Ford tolerances used on anything other than our valve, it was stated by a Ford Supplier Quality Manager that indeed today's engines do have tighter tolerances than those once produced. Higher pressures are run in today's engines. The sole purpose of engine oil is no longer just for lubrication. Engine oil is also used to control components such as cam phasers/valves.

The clearance used in the cam phasing valve in the 5.4 and 4.6L (2005+) (body and spool) engine is a mere 3 to 7 microns (0.00011"/0.00027". To put this into perspective I believe if memory serves me a standard human hair is 0.010". So split a hair 9 to10 times and that's the clearance between the 2 most critical parts which depend on engine oil to function properly.

Countless hours are spent in Engineering, Development, Durability, etc in designing these systems to function through their 100 million life cycles. Many factors of course can contribute their improper function. However improper oil weight will certainly not allow proper phasing of the cams. You may not even see a check engine light, however I'm quite certain you won't be seeing or feeling the optimum performance you would if you were using the proper oil weight.

moosestang

So your saying the 5.4 and 4.6 have the same cam phaser tolerances? You realize one calls for 5w20 and the other 5w50 right?

I've been using 5w30 for 5 years and 30,000 plus miles. I don't trust a 5w20 for protecting my engine with the way I drive it. Might as well put olive oil in there, that **** is thin.

I wish i had an oil pressure gauge and I'd do some testing with 5w20/5w30 and 5w40.

ford switched to 5w20 to meet CAFE standards, that was without changing anything in the 4.6

Now if you could find me 1 motorcycle engine that specs 5w20, then I might believe the regurgitated tighter tolerances BS that everyone keeps repeating. You won't find one, because they don't give a pooh about CAFE.

Woodys2718

Yes, they are exactly the same part number. Keep in my mind though, these are two different motors and I can't speak for the phasers at all... don't know if they are the same. I'm sure the cams are different also.